Re: [Elecraft] K2 BFO test failed

[Mike Maiorana]

Don,
My replacement BFO crystals arrived today and I installed them. My BFO
range is now 5.66 kHz. FIXED! Thank you!

I have to add a note about what I call "Elecraft Mojo". The crystals were
back ordered so there was a delay before they could be shipped. The package
was sent Friday from California on its way to Florida. USPS web page said
that the package would deliver on Monday. I checked the tracking info this
morning (Sunday) and it said that the package was at the local sorting
facility. So, on track for a Monday delivery. I went out to the mailbox to
drop off an outgoing letter this afternoon and I was surprised to see a
Priority Mail box inside. Sure enough, it was my Elecraft parts order,
delivered by the USPS ON SUNDAY!!! To make sure I wasn't losing my mind I
checked the tracking info again and sure enough, it was sorted and
delivered today. I have NEVER received regular mail on a Sunday. Just more
of that Elecraft Mojo.

And, of course, my tiny little order was treated with the same urgency and
respect as when I bought the radio new. What a great company.

Now, off to finish the alignment!
Thanks again and 73
Mike M.
KU4QO

On Sat, Sep 30, 2017 at 10:53 PM, Mike Maiorana  wrote:

> Don,
> Thank you again for your very detailed response. I think I've found the
> problem.
> After doing the visual checks you suggested I wanted to try and isolate
> the crystals to see if the problem was there.
> I left L33 alone and carefully removed the BFO crystal that was accessible
> without removing the inductor. Now CAL FCTR showed the BFO frequency as
> 0. Interesting.
>
> I then removed L33 and the second BFO crystal. Using a simple crystal
> tester/oscillator I have showed the second crystal (the one under L33) did
> not oscillate. The other crystal seemed to oscillate fine. So, it looks
> like an order for a pair of BFO crystals should get me back in business, or
> at least let me continue the alignment. Hopefully this was the only problem.
>
> Thanks again Don for your expert advice. I'll follow up when I get the
> replacement parts.
> Best regards and 73
> Mike M.
> KU4QO
>
>>
>>> I'm having an issue at the BFO test. The BFO high frequency is
>>> 4916.04 kHz
>>> and the low frequency is 4913.82 kHz. That's a difference of
>>> 2.19 kHz, well
>>> below the 3.6 kHz stated minimum.
>>>
>>>
>>>
>>
>
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Re: [Elecraft] K2 BFO test failed

[Mike Maiorana]

Don,
Thank you again for your very detailed response. I think I've found the
problem.
After doing the visual checks you suggested I wanted to try and isolate the
crystals to see if the problem was there.
I left L33 alone and carefully removed the BFO crystal that was accessible
without removing the inductor. Now CAL FCTR showed the BFO frequency as
0. Interesting.

I then removed L33 and the second BFO crystal. Using a simple crystal
tester/oscillator I have showed the second crystal (the one under L33) did
not oscillate. The other crystal seemed to oscillate fine. So, it looks
like an order for a pair of BFO crystals should get me back in business, or
at least let me continue the alignment. Hopefully this was the only problem.

Thanks again Don for your expert advice. I'll follow up when I get the
replacement parts.
Best regards and 73
Mike M.
KU4QO

On Sat, Sep 30, 2017 at 6:12 PM, Don Wilhelm  wrote:

> Mike,
>
> How did you check the value of the resistor.  If you used your DMM while
> it was in-circuit, then you have an open L33.  The BFO would oscillate, but
> the range would be restricted as yours is or more narrow.
>
> First thing, check capacitors C173 and C174 to be certain you have the
> correct values installed.  Those blue capacitors with the yellow printing
> on them are difficult to read, so use a magnifier and lots of light.
>
> Then check D37 and D38 to be certain they are oriented correctly - the
> slightly angled side is the "rounded" side.
>
> Make certain RP6 is well soldered - reflow with a hot iron (750 degF) and
> apply a bit of extra solder - you really one need the flux.  The iron dwell
> time should be about 3 seconds, but watch for the solder to flow out onto
> both the solder pad and the component lead to assure good soldering - up to
> 5 seconds dwell will not hurt anything.
>
> Then when doing the BFO Hi and BFO LO frequency checks make sure RP6 pin 7
> goes to quite near 5 volts and also quite near zero volts.
>
> The above are the easiest items to check.
> Keep in mind that the resistor which holds L33 is really an insulator, it
> serves no electrical function.
>
> You are correct that a bad BFO crystal could cause the problem, but to
> change them (change them as a matched pair), you have to lift L33.  Not too
> bad is you are careful, leave the leads connected to the resistor leads,
> heat the solder pad and pull the resistor lead out - repeat for the other
> side and lift L33 and the resistor off as an assembly.
>
> So try the easy stuff first, and if that does not cure it, contact
> Elecraft Support and request a pair of BFO crystals and a new L33 and 5.1
> meg resistor to replace them.
>
> 73,
> Don W3FPR
>
> On 9/30/2017 5:40 PM, Mike Maiorana wrote:
>
>> Thanks Don.
>> I triple-checked the inductor wires and they are well soldered to the
>> pads. I also verified the value of the resistor across it, 5.1 Mohms. I
>> reflowed the solder anyway, but no change in the BFO frequency range.
>>
>> If L33 wasn't connected would the oscillator even run?
>>
>> If one of the two crystals was bad (or not soldered properly) would you
>> also see a reduction in BFO range?
>> What about if one of the varactors had failed?
>>
>> Any further advice will be greatly appreciated.
>> Thanks and 73
>> Mike M.
>> KU4QO
>>
>> On Sat, Sep 30, 2017 at 9:57 AM, Don Wilhelm > > wrote:
>>
>> Mike,
>>
>> The inadequate BFO range is usually a result of the L33 toroid
>> leads not being well soldered.  The toroid wires are very fine and
>> sometimes are not visible to the naked eye, so use magnification
>> to examine them. When re-soldering, use a pointed tool to bring
>> the fine toroid wires down onto the solder pad instead of further
>> up on the securing resistor lead.
>>
>> For adjusting the 4 MHz Reference Oscillator (that has nothing to
>> do with the BFO range), refer to the K2 Dial Calibration article
>> on my website www.w3fpr.com  for the most
>>
>> accurate method of adjusting the Reference Oscillator.
>>
>> Be aware that the 4 MHz Reference oscillator can drift in normal
>> operation, so soon after adjusting it, run CAL PLL and CAL FIL
>> while it is still "on frequency".  That oscillator is not used in
>> operation for the K2 frequency display.  In other words, simply
>> adjusting the 4 MHz Reference does nothing for normal operation.
>>
>> 73,
>> Don W3FPR
>>
>>
>> On 9/30/2017 9:35 AM, Mike Maiorana wrote:
>>
>> Hello all. I have a K2, 6000+ serial number, that I'm trying
>> to get working
>> correctly. Unknown history. A quick test showed the filters
>> were not
>> properly adjusted (could hear both sidebands of carrier on
>> some bands). I
>> thought it would be best to do a top-down alignment.
>>
>> I adjusted the 4 MHz oscillator, 

Re: [Elecraft] K2 BFO test failed

[Don Wilhelm]

Mike,

How did you check the value of the resistor.  If you used your DMM while 
it was in-circuit, then you have an open L33.  The BFO would oscillate, 
but the range would be restricted as yours is or more narrow.


First thing, check capacitors C173 and C174 to be certain you have the 
correct values installed.  Those blue capacitors with the yellow 
printing on them are difficult to read, so use a magnifier and lots of 
light.


Then check D37 and D38 to be certain they are oriented correctly - the 
slightly angled side is the "rounded" side.


Make certain RP6 is well soldered - reflow with a hot iron (750 degF) 
and apply a bit of extra solder - you really one need the flux.  The 
iron dwell time should be about 3 seconds, but watch for the solder to 
flow out onto both the solder pad and the component lead to assure good 
soldering - up to 5 seconds dwell will not hurt anything.


Then when doing the BFO Hi and BFO LO frequency checks make sure RP6 pin 
7 goes to quite near 5 volts and also quite near zero volts.


The above are the easiest items to check.
Keep in mind that the resistor which holds L33 is really an insulator, 
it serves no electrical function.


You are correct that a bad BFO crystal could cause the problem, but to 
change them (change them as a matched pair), you have to lift L33.  Not 
too bad is you are careful, leave the leads connected to the resistor 
leads, heat the solder pad and pull the resistor lead out - repeat for 
the other side and lift L33 and the resistor off as an assembly.


So try the easy stuff first, and if that does not cure it, contact 
Elecraft Support and request a pair of BFO crystals and a new L33 and 
5.1 meg resistor to replace them.


73,
Don W3FPR

On 9/30/2017 5:40 PM, Mike Maiorana wrote:

Thanks Don.
I triple-checked the inductor wires and they are well soldered to the 
pads. I also verified the value of the resistor across it, 5.1 Mohms. 
I reflowed the solder anyway, but no change in the BFO frequency range.


If L33 wasn't connected would the oscillator even run?

If one of the two crystals was bad (or not soldered properly) would 
you also see a reduction in BFO range?

What about if one of the varactors had failed?

Any further advice will be greatly appreciated.
Thanks and 73
Mike M.
KU4QO

On Sat, Sep 30, 2017 at 9:57 AM, Don Wilhelm > wrote:


Mike,

The inadequate BFO range is usually a result of the L33 toroid
leads not being well soldered.  The toroid wires are very fine and
sometimes are not visible to the naked eye, so use magnification
to examine them. When re-soldering, use a pointed tool to bring
the fine toroid wires down onto the solder pad instead of further
up on the securing resistor lead.

For adjusting the 4 MHz Reference Oscillator (that has nothing to
do with the BFO range), refer to the K2 Dial Calibration article
on my website www.w3fpr.com  for the most
accurate method of adjusting the Reference Oscillator.

Be aware that the 4 MHz Reference oscillator can drift in normal
operation, so soon after adjusting it, run CAL PLL and CAL FIL
while it is still "on frequency".  That oscillator is not used in
operation for the K2 frequency display.  In other words, simply
adjusting the 4 MHz Reference does nothing for normal operation.

73,
Don W3FPR


On 9/30/2017 9:35 AM, Mike Maiorana wrote:

Hello all. I have a K2, 6000+ serial number, that I'm trying
to get working
correctly. Unknown history. A quick test showed the filters
were not
properly adjusted (could hear both sidebands of carrier on
some bands). I
thought it would be best to do a top-down alignment.

I adjusted the 4 MHz oscillator, verified the PLL reference
oscillator
range (12.43 kHz), VCO test and VCO alignment. No problems up
to that
point.

I'm having an issue at the BFO test. The BFO high frequency is
4916.04 kHz
and the low frequency is 4913.82 kHz. That's a difference of
2.19 kHz, well
below the 3.6 kHz stated minimum.




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Re: [Elecraft] K2 BFO test failed

[Mike Maiorana]

Thanks Don.
I triple-checked the inductor wires and they are well soldered to the pads.
I also verified the value of the resistor across it, 5.1 Mohms. I reflowed
the solder anyway, but no change in the BFO frequency range.

If L33 wasn't connected would the oscillator even run?

If one of the two crystals was bad (or not soldered properly) would you
also see a reduction in BFO range?
What about if one of the varactors had failed?

Any further advice will be greatly appreciated.
Thanks and 73
Mike M.
KU4QO

On Sat, Sep 30, 2017 at 9:57 AM, Don Wilhelm  wrote:

> Mike,
>
> The inadequate BFO range is usually a result of the L33 toroid leads not
> being well soldered.  The toroid wires are very fine and sometimes are not
> visible to the naked eye, so use magnification to examine them. When
> re-soldering, use a pointed tool to bring the fine toroid wires down onto
> the solder pad instead of further up on the securing resistor lead.
>
> For adjusting the 4 MHz Reference Oscillator (that has nothing to do with
> the BFO range), refer to the K2 Dial Calibration article on my website
> www.w3fpr.com for the most accurate method of adjusting the Reference
> Oscillator.
>
> Be aware that the 4 MHz Reference oscillator can drift in normal
> operation, so soon after adjusting it, run CAL PLL and CAL FIL while it is
> still "on frequency".  That oscillator is not used in operation for the K2
> frequency display.  In other words, simply adjusting the 4 MHz Reference
> does nothing for normal operation.
>
> 73,
> Don W3FPR
>
>
> On 9/30/2017 9:35 AM, Mike Maiorana wrote:
>
>> Hello all. I have a K2, 6000+ serial number, that I'm trying to get
>> working
>> correctly. Unknown history. A quick test showed the filters were not
>> properly adjusted (could hear both sidebands of carrier on some bands). I
>> thought it would be best to do a top-down alignment.
>>
>> I adjusted the 4 MHz oscillator, verified the PLL reference oscillator
>> range (12.43 kHz), VCO test and VCO alignment. No problems up to that
>> point.
>>
>> I'm having an issue at the BFO test. The BFO high frequency is 4916.04 kHz
>> and the low frequency is 4913.82 kHz. That's a difference of 2.19 kHz,
>> well
>> below the 3.6 kHz stated minimum.
>>
>>
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Re: [Elecraft] K2 BFO test failed

[Don Wilhelm]

Mike,

The inadequate BFO range is usually a result of the L33 toroid leads not 
being well soldered.  The toroid wires are very fine and sometimes are 
not visible to the naked eye, so use magnification to examine them. 
When re-soldering, use a pointed tool to bring the fine toroid wires 
down onto the solder pad instead of further up on the securing resistor 
lead.


For adjusting the 4 MHz Reference Oscillator (that has nothing to do 
with the BFO range), refer to the K2 Dial Calibration article on my 
website www.w3fpr.com for the most accurate method of adjusting the 
Reference Oscillator.


Be aware that the 4 MHz Reference oscillator can drift in normal 
operation, so soon after adjusting it, run CAL PLL and CAL FIL while it 
is still "on frequency".  That oscillator is not used in operation for 
the K2 frequency display.  In other words, simply adjusting the 4 MHz 
Reference does nothing for normal operation.


73,
Don W3FPR

On 9/30/2017 9:35 AM, Mike Maiorana wrote:

Hello all. I have a K2, 6000+ serial number, that I'm trying to get working
correctly. Unknown history. A quick test showed the filters were not
properly adjusted (could hear both sidebands of carrier on some bands). I
thought it would be best to do a top-down alignment.

I adjusted the 4 MHz oscillator, verified the PLL reference oscillator
range (12.43 kHz), VCO test and VCO alignment. No problems up to that
point.

I'm having an issue at the BFO test. The BFO high frequency is 4916.04 kHz
and the low frequency is 4913.82 kHz. That's a difference of 2.19 kHz, well
below the 3.6 kHz stated minimum.


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[Elecraft] K2 BFO test failed

[Mike Maiorana]

Hello all. I have a K2, 6000+ serial number, that I'm trying to get working
correctly. Unknown history. A quick test showed the filters were not
properly adjusted (could hear both sidebands of carrier on some bands). I
thought it would be best to do a top-down alignment.

I adjusted the 4 MHz oscillator, verified the PLL reference oscillator
range (12.43 kHz), VCO test and VCO alignment. No problems up to that
point.

I'm having an issue at the BFO test. The BFO high frequency is 4916.04 kHz
and the low frequency is 4913.82 kHz. That's a difference of 2.19 kHz, well
below the 3.6 kHz stated minimum.

I verified the crystals at X3 and X4 were the correct type, along with the
values of D37, D38, C173 and C174. I didn't see any PCB trace damage in the
area. I reflowed the solder on those pins but didn't see a significant
change in the BFO frequency range. I checked the VBFO control voltage and
had 7.81 V at the high BFO frequency down to 0.00 V at the low BFO
frequency.

Any advice on how to move forward?

Thanks and 73,
Mike M.
KU4QO
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Re: [Elecraft] K2 BFO Test fails

[kruegerbenny]

Today I ordered a new L33 and X3/X4, will write as soon as they arrived ...

At this point: thank you Don for your indefatigable help!

Benny
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Re: [Elecraft] K2 BFO Test fails

[Don Wilhelm]

  Benny,

R116 is supposed to be a very high value resistor - in fact, it would be 
best if it were actually an insulator, but 5.1 megohms is sufficiently 
high to serve that purpose.  The only reason the resistor is provided is 
that it produces both a mounting anchor for L33 and its leads provide a 
place to solder the fine wires.

It sounds like you have a bad L33 or one end that is not actually 
soldered.  Make certain the tinned part of the very fine wire is 
actually soldered to the lead of R116.
If it is well soldered, request a replacement L33 from 
parts(at)elecraft(dot)com.

73,
Don W3FPR

On 12/4/2010 8:03 PM, kruegerbenny wrote:
 Hi,

 grounding of L33 doesn't bring the expected signal (7.xMHz). D37 seems to be
 mounted the right way (round caps in direction to front panel).
 If I put a resistor parallel to R116(it should be the right one:
 grn-brw-grn-(gold)), i get the 4.9MHz oscillation, but still no signal at
 TP2 (in this case, i get the following frequencies by contacting the int.
 probe to U11-P7: 4918.75 and 4916.12).


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Re: [Elecraft] K2 BFO Test fails

[kruegerbenny]

So, hello again.

First of all i want to excuse but I give you some false informations. The
8.x MHz signal I measured was/is at Pin 7, not Pin 6 of U11. I did the test
with grounding L33/X3/X4 and there's some interesting behaviour (at Pin 7):
When I ground L33/X3/X4, the measured signal is about 7.7MHz. By removing
the jumper(to ground), the frequency changes to 4.9MHz. 

After that, I changed the order of instructions:
Now I connect the probe at P7(U11) and then ground L33/X3/X4. The result:
Before grounding 8.02MHz, after grounding 4.9MHz (also when I remove the
jumper)

Benny


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Re: [Elecraft] K2 BFO Test fails

[Don Wilhelm]

  Benny,

Actually you should have a better signal at U11 pin 6 than you do at pin 
7, but let that go for right now (we may get back to it if necessary).

So you do get the proper BFO frequency when grounding the crystals, and 
as I recall you measured a low resistance across L33, so it should have 
continuity - all that should be good.

Now, monitor the oscillation at U11 pin 6 (or pin 7) while you ground 
the side of L33 that is NOT connected to X4 and X5.
Ignore any oscillation other than the 4.9 kHz because that is what you 
are looking for.

If you get a 4.9 kHz oscillation with the low end of L33 connected to 
ground, then check the value of C172 - it should be 0.01 uF (marked 
103).  Also verify again that D37 is mounted the right way 'round.

If you cannot get a 4.9 kHz oscillation with the lower end of L33 
grounded, inspect the soldering of those fine wires to the leads of the 
1/8 watt resistor very carefully - and make sure what you used for that 
high value 1/8 watt resistor was the correct item.  It is a very high 
value resistor, and is actually used as an effective insulator across 
L33 to both solder the fine wire leads and secure L33.  If you used 
anything else, that could cause your problems.

73,
Don W3FPR

On 12/4/2010 1:47 PM, kruegerbenny wrote:
 So, hello again.

 First of all i want to excuse but I give you some false informations. The
 8.x MHz signal I measured was/is at Pin 7, not Pin 6 of U11. I did the test
 with grounding L33/X3/X4 and there's some interesting behaviour (at Pin 7):
 When I ground L33/X3/X4, the measured signal is about 7.7MHz. By removing
 the jumper(to ground), the frequency changes to 4.9MHz.

 After that, I changed the order of instructions:
 Now I connect the probe at P7(U11) and then ground L33/X3/X4. The result:
 Before grounding 8.02MHz, after grounding 4.9MHz (also when I remove the
 jumper)

 Benny


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Re: [Elecraft] K2 BFO Test fails

[kruegerbenny]

Hi,

grounding of L33 doesn't bring the expected signal (7.xMHz). D37 seems to be
mounted the right way (round caps in direction to front panel).
If I put a resistor parallel to R116(it should be the right one:
grn-brw-grn-(gold)), i get the 4.9MHz oscillation, but still no signal at
TP2 (in this case, i get the following frequencies by contacting the int.
probe to U11-P7: 4918.75 and 4916.12). 


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Re: [Elecraft] K2 BFO Test fails

[Don Wilhelm]

  Benny,

Thanks for providing your name, and very good luck on acquiring your 
amateur license.
I am also adding K2 to the subject - some here like to filter by rig type.

OK, first the frequency is wrong, are you certain you have the time 
scale on your 'scope calibrated?  The K2 BFO crystals should be marked 
for 4915 kHz (or something near that) - check those markings first.

Then check continuity through L33 with your ohmmeter - it is best 
checked from the top of the board which will check for improperly 
soldered connections too.  If the resistance is quite high, you may have 
an open L33 or an improper solder connection.

Also check D37 to be certain it is not installed backwards - that could 
kill the BFO signal.

Check for a solder bridge at pins 3, 4, 5 and 6 of RP6 - that also will 
kill the signal.

73,
Don W3FPR


On 12/3/2010 4:50 PM, kruegerbenny wrote:
 Q24: 5,76V

 L33(left): 8,33MHz(240mV peak-to-peak)
 L33(right): no signal (i think here is the lost)


 I have to admit that I don't have a call sign yet, but I'm already learning
 for the exam (I'm a student a had a lot to do the the last months..)

 Thanks for your help

 Benny
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Re: [Elecraft] K2 BFO Test fails

[kruegerbenny]

crystal values checked - ok
continuity of L33 checked - ok
D37 is correctly installed
and I resoldered all pins of RP6

any other ideas?

(how can I check if the crystals are ok?)

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Re: [Elecraft] K2 BFO Test fails

[Don Wilhelm]

  Benny,

Well, if all that is OK, then it should work unless there is a problem 
with Q24.  Check the value of C169 as well as C173 and C174.

It is particularly worrysome that you are seeing something around 8 MHz 
at pin 6 of U11.  Please tell us how you are measuring that frequency 
('scope or frequency counter).

If indeed you are getting an 8 MHz signal, you may have bad crystals at 
X3 and X4, but that would be quite unusual.
There is not an easy method of checking the crystals.

You may want to beg parts(at) elecraft(dot)com for replacement BFO 
crystals and a replacement L33.

Please include your name on all posts to this reflector.

73,
Don W3FPR

On 12/3/2010 7:03 PM, kruegerbenny wrote:
 crystal values checked -  ok
 continuity of L33 checked -  ok
 D37 is correctly installed
 and I resoldered all pins of RP6

 any other ideas?

 (how can I check if the crystals are ok?)

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Re: [Elecraft] K2 BFO Test fails

[Don Wilhelm]

  Benny,

Additional thoughts - check D38 for correct orientation.
Try putting a jumper from the junction on L33, X3 and X4 to see if you 
get oscillation at 4915 kHz or something close to that frequency - if 
you do, the crystals are OK and your problem is with L33, D37, C169 or Q24.

73,
Don W3FPR


On 12/3/2010 7:03 PM, kruegerbenny wrote:
 crystal values checked -  ok
 continuity of L33 checked -  ok
 D37 is correctly installed
 and I resoldered all pins of RP6

 any other ideas?

 (how can I check if the crystals are ok?)

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Re: [Elecraft] K2 BFO Test fails

[kruegerbenny]

I will do the tests tomorrow, but one question: 
A jumper from junction of l33,x3 and x4 to where?

Benny

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Re: [Elecraft] K2 BFO Test fails

[Don Wilhelm]

  Benny,

To ground.

73,
Don W3FPR

On 12/3/2010 8:15 PM, kruegerbenny wrote:
 I will do the tests tomorrow, but one question:
 A jumper from junction of l33,x3 and x4 to where?

 Benny

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[Elecraft] K2 BFO Test problems ( Align. and test, Part II )

[Toni Martin]

Hi all,

In the process to test and alignement Part II, I have
the following issue:  I don´t get the correct range of
BFO values. In my case the set of values are:

- Using CAL FCTR  ...  4913,63 Khz.
- BFO High Freq. ..  0,00
- BFO Low Freq   4912,60 Khz.

When I try to set up all filters following the
instruccions on page 93, I  have got the correct
values in CW Norm. and LSB modes, but I can´t get the
correct values in CW Rev. / USB modes. The maximun
value that I can get in this modes is  4914,00 Khz.
The rest of tests included in this section are
corrects

Note:  In my K2 kit I don´t  received ( or I have lost
it  ) the diode D36 - SMT1B and I have replaced it
(temporarily) for an IN4007. Could be this change the
reason of my troubles ???.

Of course, I checked and re-checked the values and
solders of all the components involved in the BFO
schematics ( L33, D37, D38, C169, C173, C174, X3 and
X4 )

All suggestions will be appreciated.

73´s
Toni, ea3gby
( K2 - s/n 6379 in building process )


  

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Re: [Elecraft] K2 BFO Test Problems

[Craig Young]

All,

I thought I'd write describing what the issue was for the record.  In  
the end it was a bad connection on U10 of the Control Board.  Pin 13  
was not soldered correctly, so V BFO was incorrect.  When tested on  
the RF board V BFO did not move between 0 and 8 Vdc as required (it  
hovered around 5.5 Vdc).  I much appreciate the effort of Gary AB7MY  
at Elecraft for helping me track this down.


73,

Craig AC6NN


On 19 Feb, 2007, at 0:17, Don Wilhelm wrote:


Craig,

The problem is most likely in one of the following  areas:
1) The L33 inductor
2) The varactors
3) The crystals themselves.

The very most likely problem is a poor solder connection, and the  
second

most likely is misplaced components.
The DC voltages look to be within reason, and it is probably not  
the fault

of U11.

We can get to precise measuremnts tomorrow, it is getting late here  
today.


73,
Don W3FPR


-Original Message-

Hello again,

I've continued my troubleshooting efforts but the problem persists.
I had reflowed all connections except those of X3, so I removed L33
and R116 to do so.  Everything appears to be well connected and I
don't see any shorts.

I checked the DC voltages on U11 using the internal probe and have
the following values:

Pin 1:  1.4
Pin 2:  1.4
Pin 3:  0.0
Pin 4:  4.8
Pin 5:  4.8
Pin 6:  5.6
Pin 7:  5.0
Pin 8:  6.0

I used the RF probe to check the voltages with the following results:

U11, pin 6: 0.74
TP2:0.024

The DC voltages for U11 pins 6 and 7 are a bit low and the RF probe
values are on the edges.  Is it possible that U11 is bad?

73,

Craig


On 18 Feb, 2007, at 10:46, Craig Young wrote:


Hello to the group.

I am currently working through the Alignment and Test, Part II and
have run into the following issue.  When I perform the BFO Test, I
don't get the proper range.  The set of values I get are:

BFO High Freq.: 4917.31 kHz
BFO Low Freq.:  4916.97 kHz
Range: 0.34 kHz

The documentation states that if the BFO range is less than 3.6
kHz, the varactor diodes (D37 and D38) or the crystals (X3 and X4)
may be incorrect.  However, I've verified them and they are
correct.  I've also gone around looking for bad soldering (cold
joints or bridges) and didn't see anything obvious.  I've checked
the resistors and capacitors in the BFO section and they appear to
be correct.

Does anyone have any ideas of where I should look next?

73,

Craig AC6NN

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[Elecraft] K2 BFO Test Problems

[Craig Young]

Hello to the group.

I am currently working through the Alignment and Test, Part II and  
have run into the following issue.  When I perform the BFO Test, I  
don't get the proper range.  The set of values I get are:


BFO High Freq.: 4917.31 kHz
BFO Low Freq.:  4916.97 kHz
Range: 0.34 kHz

The documentation states that if the BFO range is less than 3.6 kHz,  
the varactor diodes (D37 and D38) or the crystals (X3 and X4) may be  
incorrect.  However, I've verified them and they are correct.  I've  
also gone around looking for bad soldering (cold joints or bridges)  
and didn't see anything obvious.  I've checked the resistors and  
capacitors in the BFO section and they appear to be correct.


Does anyone have any ideas of where I should look next?

73,

Craig AC6NN

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Re: [Elecraft] K2 BFO Test Problems

[Craig Young]

Hello again,

I've continued my troubleshooting efforts but the problem persists.   
I had reflowed all connections except those of X3, so I removed L33  
and R116 to do so.  Everything appears to be well connected and I  
don't see any shorts.


I checked the DC voltages on U11 using the internal probe and have  
the following values:


Pin 1:  1.4
Pin 2:  1.4
Pin 3:  0.0
Pin 4:  4.8
Pin 5:  4.8
Pin 6:  5.6
Pin 7:  5.0
Pin 8:  6.0

I used the RF probe to check the voltages with the following results:

U11, pin 6: 0.74
TP2:0.024

The DC voltages for U11 pins 6 and 7 are a bit low and the RF probe  
values are on the edges.  Is it possible that U11 is bad?


73,

Craig


On 18 Feb, 2007, at 10:46, Craig Young wrote:


Hello to the group.

I am currently working through the Alignment and Test, Part II and  
have run into the following issue.  When I perform the BFO Test, I  
don't get the proper range.  The set of values I get are:


BFO High Freq.: 4917.31 kHz
BFO Low Freq.:  4916.97 kHz
Range: 0.34 kHz

The documentation states that if the BFO range is less than 3.6  
kHz, the varactor diodes (D37 and D38) or the crystals (X3 and X4)  
may be incorrect.  However, I've verified them and they are  
correct.  I've also gone around looking for bad soldering (cold  
joints or bridges) and didn't see anything obvious.  I've checked  
the resistors and capacitors in the BFO section and they appear to  
be correct.


Does anyone have any ideas of where I should look next?

73,

Craig AC6NN

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RE: [Elecraft] K2 BFO Test Problems

[Don Wilhelm]

Craig,

The problem is most likely in one of the following  areas:
1) The L33 inductor
2) The varactors
3) The crystals themselves.

The very most likely problem is a poor solder connection, and the second
most likely is misplaced components.
The DC voltages look to be within reason, and it is probably not the fault
of U11.

We can get to precise measuremnts tomorrow, it is getting late here today.

73,
Don W3FPR

 -Original Message-

 Hello again,

 I've continued my troubleshooting efforts but the problem persists.
 I had reflowed all connections except those of X3, so I removed L33
 and R116 to do so.  Everything appears to be well connected and I
 don't see any shorts.

 I checked the DC voltages on U11 using the internal probe and have
 the following values:

 Pin 1:1.4
 Pin 2:1.4
 Pin 3:0.0
 Pin 4:4.8
 Pin 5:4.8
 Pin 6:5.6
 Pin 7:5.0
 Pin 8:6.0

 I used the RF probe to check the voltages with the following results:

 U11, pin 6:   0.74
 TP2:  0.024

 The DC voltages for U11 pins 6 and 7 are a bit low and the RF probe
 values are on the edges.  Is it possible that U11 is bad?

 73,

 Craig


 On 18 Feb, 2007, at 10:46, Craig Young wrote:

  Hello to the group.
 
  I am currently working through the Alignment and Test, Part II and
  have run into the following issue.  When I perform the BFO Test, I
  don't get the proper range.  The set of values I get are:
 
  BFO High Freq.: 4917.31 kHz
  BFO Low Freq.:  4916.97 kHz
  Range: 0.34 kHz
 
  The documentation states that if the BFO range is less than 3.6
  kHz, the varactor diodes (D37 and D38) or the crystals (X3 and X4)
  may be incorrect.  However, I've verified them and they are
  correct.  I've also gone around looking for bad soldering (cold
  joints or bridges) and didn't see anything obvious.  I've checked
  the resistors and capacitors in the BFO section and they appear to
  be correct.
 
  Does anyone have any ideas of where I should look next?
 
  73,
 
  Craig AC6NN
 
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[Elecraft] K2 BFO Test Range Question

[SABorns]

In doing BFO Test (pg62) my BFO Low Freq. is 4912..87. The  manual says it 
should be less than 4912.7. Will this cause a problem? The BFO  range from high 
to low is 4.39kHz
73, Steve K8IDN
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[Elecraft] K2 BFO Test Problem Solved (again)

[SABorns]

Problem solved. I am feeling a little stupid at the moment. I  had the same 
issue with another K2 that I built some time ago but forgot the  solution. I 
fixed the problem by adding a 2pf cap from the  junction of X3, X4 and L33 to 
ground.  My brain must be going.
73, Steve K8IDN
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Re: [Elecraft] K2 BFO Test

[Bill Coleman]

On Dec 9, 2005, at 8:56 AM, Don Brown wrote:

I have used this method on 3 or 4 of the K2's I have built. I use a  
1pF or
2pF NPO cap to lower the bottom end of the range to get it to meet  
the spec.
I agree with you on pulling the crystal much with this method. I  
would not
recommend cap values above maybe 3 or 4 pF. I have never needed  
more than 1
pf. Padding C173 and C174 is a better method if the radio needs  
more than 1
or 2 pf. I believe this method was suggested by Gary at Elecraft  
some time
back. At any rate it is a little easier to do than the padding or  
change out

of C174 and C173


To get the BFO range I needed for RTTY, not only did I have to pad  
C173 and 4, but after I had added maximum capacitance there, I went  
ahead and added 2 pF to pull the crystal. I have not noticed any  
stability problems, and the BFO range is just about perfect.


Bill Coleman, AA4LR, PP-ASELMail: [EMAIL PROTECTED]
Quote: Not within a thousand years will man ever fly!
-- Wilbur Wright, 1901

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RE: RE: [Elecraft] K2 BFO Test

[Don Wilhelm]

Don B.

Thanks for that information - it adds credibility to that method along with
a good dose of common sense.

Don W. W3FPR

 -Original Message-

 Hi Don and All

 I have used this method on 3 or 4 of the K2's I have built. I use
 a 1pF or
 2pF NPO cap to lower the bottom end of the range to get it to
 meet the spec.
 I agree with you on pulling the crystal much with this method. I
 would not
 recommend cap values above maybe 3 or 4 pF. I have never needed
 more than 1
 pf. Padding C173 and C174 is a better method if the radio needs
 more than 1
 or 2 pf. I believe this method was suggested by Gary at Elecraft
 some time
 back. At any rate it is a little easier to do than the padding or
 change out
 of C174 and C173


 The other Don

 Don Brown
 KD5NDB



 - Original Message -
 From: Don Wilhelm [EMAIL PROTECTED]
 To: [EMAIL PROTECTED]; [EMAIL PROTECTED]; elecraft@mailman.qth.net
 Sent: Thursday, December 08, 2005 5:03 PM
 Subject: RE: RE: [Elecraft] K2 BFO Test


  Sverre,
 
  I have not tried that small capacitor from the junction of the crystals
  and
  L33 so I cannot comment on it from that standpoint.
 
  What I would like to state is that when one pulls a crystal by
 any method,
  the stability becomes worse as the amount of pulling becomes
 greater.  One
  should be aware of this and related facts when modifying any
 circuit in a
  way that is not 'approved and tested'.  Also due to the nature of
  crystals,
  something that happens to work in one situation may not work
 the same for
  all cases.  Remember that I am only bringing up cautions here, I am not
  makeing a firm statement about the operation one way or another.
 
  It certainly would be nice if someone (or better yet, several someones)
  with
  access to suitable instrumentation could try this or any other mod and
  report the results.  The fact that it worked on a sample of one does not
  create a statement that it will work in other cases - that is simple
  statistical knowledge - I would like to see something that says
 it works
  in
  at least 5 or 10 trials before drawing any firm conclusions.
 
  So, yes I think it should be left on your website, but you may
 want to put
  a
  Use at your own peril disclaimer on all those that are not
 'approved by
  Elecraft' or otherwise adequately tested (and I invite you to
 add any of
  my
  mods to that group as well, even though I have absolute
 confidence in my
  own
  work).
 
  73,
  Don W3FPR
 
   -Original Message-
   
The preferred method of padding the BFO capacitors is to
maintain the ratio between C173 and C174 by paralleling them
with capacitors.  A single capacitor from the junction to
ground will be in parallel with the series combination of
C173 and the varactor D38 and could make the BFO less stable
than it should be.
   
  
   Don,
  
   How about a single capacitor (1-4 pF) from the junction of the
   crystals and
   the L33 inductor as in
  
http://www.ac6rm.net/mailarchive/html/elecraft-list/2005-08/msg00562.html?
  Does that create potential stability problems also?
 
  I've got this link on my K2 mods page and just wanted to make sure I can
  recommend it and keep it there. I have never had any problems
  with BFO range
  myself so I have no personal experience with this myself.
 
  73
 
  Sverre
  LA3ZA
  http://www.qslnet.de/la3za/
 

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Re: RE: [Elecraft] K2 BFO Test

[Don Brown]

Hi Don and All

I have used this method on 3 or 4 of the K2's I have built. I use a 1pF or 
2pF NPO cap to lower the bottom end of the range to get it to meet the spec. 
I agree with you on pulling the crystal much with this method. I would not 
recommend cap values above maybe 3 or 4 pF. I have never needed more than 1 
pf. Padding C173 and C174 is a better method if the radio needs more than 1 
or 2 pf. I believe this method was suggested by Gary at Elecraft some time 
back. At any rate it is a little easier to do than the padding or change out 
of C174 and C173


The other Don

Don Brown
KD5NDB



- Original Message - 
From: Don Wilhelm [EMAIL PROTECTED]
To: [EMAIL PROTECTED]; [EMAIL PROTECTED]; elecraft@mailman.qth.net
Sent: Thursday, December 08, 2005 5:03 PM
Subject: RE: RE: [Elecraft] K2 BFO Test


 Sverre,

 I have not tried that small capacitor from the junction of the crystals 
 and
 L33 so I cannot comment on it from that standpoint.

 What I would like to state is that when one pulls a crystal by any method,
 the stability becomes worse as the amount of pulling becomes greater.  One
 should be aware of this and related facts when modifying any circuit in a
 way that is not 'approved and tested'.  Also due to the nature of 
 crystals,
 something that happens to work in one situation may not work the same for
 all cases.  Remember that I am only bringing up cautions here, I am not
 makeing a firm statement about the operation one way or another.

 It certainly would be nice if someone (or better yet, several someones) 
 with
 access to suitable instrumentation could try this or any other mod and
 report the results.  The fact that it worked on a sample of one does not
 create a statement that it will work in other cases - that is simple
 statistical knowledge - I would like to see something that says it works 
 in
 at least 5 or 10 trials before drawing any firm conclusions.

 So, yes I think it should be left on your website, but you may want to put 
 a
 Use at your own peril disclaimer on all those that are not 'approved by
 Elecraft' or otherwise adequately tested (and I invite you to add any of 
 my
 mods to that group as well, even though I have absolute confidence in my 
 own
 work).

 73,
 Don W3FPR

  -Original Message-
  
   The preferred method of padding the BFO capacitors is to
   maintain the ratio between C173 and C174 by paralleling them
   with capacitors.  A single capacitor from the junction to
   ground will be in parallel with the series combination of
   C173 and the varactor D38 and could make the BFO less stable
   than it should be.
  
 
  Don,
 
  How about a single capacitor (1-4 pF) from the junction of the
  crystals and
  the L33 inductor as in
  http://www.ac6rm.net/mailarchive/html/elecraft-list/2005-08/msg00562.html?
  Does that create potential stability problems also?
 
  I've got this link on my K2 mods page and just wanted to make sure I can
  recommend it and keep it there. I have never had any problems
  with BFO range
  myself so I have no personal experience with this myself.
 
  73
 
  Sverre
  LA3ZA
  http://www.qslnet.de/la3za/
 

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RE: RE: [Elecraft] K2 BFO Test

[Sverre Holm]

 -Original Message-
 
 The preferred method of padding the BFO capacitors is to 
 maintain the ratio between C173 and C174 by paralleling them 
 with capacitors.  A single capacitor from the junction to 
 ground will be in parallel with the series combination of 
 C173 and the varactor D38 and could make the BFO less stable 
 than it should be.
 

Don,

How about a single capacitor (1-4 pF) from the junction of the crystals and
the L33 inductor as in
http://www.ac6rm.net/mailarchive/html/elecraft-list/2005-08/msg00562.html?
Does that create potential stability problems also?

I've got this link on my K2 mods page and just wanted to make sure I can
recommend it and keep it there. I have never had any problems with BFO range
myself so I have no personal experience with this myself.

73

Sverre
LA3ZA
http://www.qslnet.de/la3za/
 

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RE: RE: [Elecraft] K2 BFO Test

[Ken K3IU]

Sverre:

This fix (that you describe) worked for me on a K2 that I built within the
past year. The LOW BFO freq was just slightly high and putting a low value
cap as you describe lowered the LOW freq to within specs, didn't change the
high BFO freq, and did not cause any instability. I don't remember the exact
value cap I used and the K2 is no longer here for me to look at.
 
73,
Ken K3IU

-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Sverre Holm
Sent: Thursday, December 08, 2005 4:07 PM
To: [EMAIL PROTECTED]; elecraft@mailman.qth.net
Subject: RE: RE: [Elecraft] K2 BFO Test

 -Original Message-
 
 The preferred method of padding the BFO capacitors is to maintain the 
 ratio between C173 and C174 by paralleling them with capacitors.  A 
 single capacitor from the junction to ground will be in parallel with 
 the series combination of
 C173 and the varactor D38 and could make the BFO less stable than it 
 should be.
 

Don,

How about a single capacitor (1-4 pF) from the junction of the crystals and
the L33 inductor as in
http://www.ac6rm.net/mailarchive/html/elecraft-list/2005-08/msg00562.html?
Does that create potential stability problems also?

I've got this link on my K2 mods page and just wanted to make sure I can
recommend it and keep it there. I have never had any problems with BFO range
myself so I have no personal experience with this myself.

73

Sverre
LA3ZA
http://www.qslnet.de/la3za/
 

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RE: RE: [Elecraft] K2 BFO Test

[Don Wilhelm]

Sverre,

I have not tried that small capacitor from the junction of the crystals and
L33 so I cannot comment on it from that standpoint.

What I would like to state is that when one pulls a crystal by any method,
the stability becomes worse as the amount of pulling becomes greater.  One
should be aware of this and related facts when modifying any circuit in a
way that is not 'approved and tested'.  Also due to the nature of crystals,
something that happens to work in one situation may not work the same for
all cases.  Remember that I am only bringing up cautions here, I am not
makeing a firm statement about the operation one way or another.

It certainly would be nice if someone (or better yet, several someones) with
access to suitable instrumentation could try this or any other mod and
report the results.  The fact that it worked on a sample of one does not
create a statement that it will work in other cases - that is simple
statistical knowledge - I would like to see something that says it works in
at least 5 or 10 trials before drawing any firm conclusions.

So, yes I think it should be left on your website, but you may want to put a
Use at your own peril disclaimer on all those that are not 'approved by
Elecraft' or otherwise adequately tested (and I invite you to add any of my
mods to that group as well, even though I have absolute confidence in my own
work).

73,
Don W3FPR

 -Original Message-
 
  The preferred method of padding the BFO capacitors is to
  maintain the ratio between C173 and C174 by paralleling them
  with capacitors.  A single capacitor from the junction to
  ground will be in parallel with the series combination of
  C173 and the varactor D38 and could make the BFO less stable
  than it should be.
 

 Don,

 How about a single capacitor (1-4 pF) from the junction of the
 crystals and
 the L33 inductor as in
 http://www.ac6rm.net/mailarchive/html/elecraft-list/2005-08/msg00562.html?
 Does that create potential stability problems also?

 I've got this link on my K2 mods page and just wanted to make sure I can
 recommend it and keep it there. I have never had any problems
 with BFO range
 myself so I have no personal experience with this myself.

 73

 Sverre
 LA3ZA
 http://www.qslnet.de/la3za/


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RE: [Elecraft] K2 BFO Test

[Don Wilhelm]

Ted,

Yes, you should get the BFO range and frequency correct - you can continue
with no extra effort, but it must be resolved eventually, and there is no
time like the present to do it.

Check the values of the capacitors C173 and C174, and while you are at it,
check C169 too.  Additionally, check the varactors D37 and D38 for the
correct type (1SV149 - the smaller ones) qne proper orientation.  Be certain
the BFO crystals were the ones you soldered in - they are typically marked
ECS D4.91 -S

If you find all the above correct, you may have to pad Capacitors C173 and
174.  Should that become necessary, use 47 pf in parallel with C174 and 120
pf in parallel with C173.  The padder capacitors will lower the low
frequency end more than the high frequency end of the range, so it should
work for you - but do the padding only if there is nothing else wrong with
the components.

73,
Don W3FPR

 -Original Message-

 I am in the process of testing the BFO on page 62.  Everything
 tested fine up to this point but now I can not get the proper BFO
 range.  The BFO high frequency is 4917.56 and the BFO low
 frequency is 4914.26.  This provides a BFO range of 3.2 kHz. It
 appears that I can not the the BFO low frequency below 4912.7 as
 specified in the manual.  I checked L33 to make sure R116 is not
 shorting any turns.  Should I troubleshoot this problem before
 proceding?  If so where else should I look.  Thanks.

 Ted K6OI


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Re: RE: [Elecraft] K2 BFO Test

[wongtheo]

All the components look right.  I guess I've got the dreaded high Q crystals.  
I've noticed in the Elecraft archives that it is possible to put a capacitor at 
the junction of X3/X4 to ground.  Which is the preferred method?  

Thanks.
 
 From: Don Wilhelm [EMAIL PROTECTED]
 Date: 2005/12/07 Wed AM 09:30:04 PST
 To: [EMAIL PROTECTED], 
   elecraft@mailman.qth.net
 Subject: RE: [Elecraft] K2 BFO Test
 
 Ted,
 
 Yes, you should get the BFO range and frequency correct - you can continue
 with no extra effort, but it must be resolved eventually, and there is no
 time like the present to do it.
 
 Check the values of the capacitors C173 and C174, and while you are at it,
 check C169 too.  Additionally, check the varactors D37 and D38 for the
 correct type (1SV149 - the smaller ones) qne proper orientation.  Be certain
 the BFO crystals were the ones you soldered in - they are typically marked
 ECS D4.91 -S
 
 If you find all the above correct, you may have to pad Capacitors C173 and
 174.  Should that become necessary, use 47 pf in parallel with C174 and 120
 pf in parallel with C173.  The padder capacitors will lower the low
 frequency end more than the high frequency end of the range, so it should
 work for you - but do the padding only if there is nothing else wrong with
 the components.
 
 73,
 Don W3FPR
 
  -Original Message-
 
  I am in the process of testing the BFO on page 62.  Everything
  tested fine up to this point but now I can not get the proper BFO
  range.  The BFO high frequency is 4917.56 and the BFO low
  frequency is 4914.26.  This provides a BFO range of 3.2 kHz. It
  appears that I can not the the BFO low frequency below 4912.7 as
  specified in the manual.  I checked L33 to make sure R116 is not
  shorting any turns.  Should I troubleshoot this problem before
  proceding?  If so where else should I look.  Thanks.
 
  Ted K6OI
 
 
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RE: RE: [Elecraft] K2 BFO Test

[Don Wilhelm]

The preferred method of padding the BFO capacitors is to maintain the ratio
between C173 and C174 by paralleling them with capacitors.  A single
capacitor from the junction to ground will be in parallel with the series
combination of C173 and the varactor D38 and could make the BFO less stable
than it should be.

You are welcome to try the single capacitor solution, but do beware of the
pitfalls.  If you would like further documentation on padding the BFO,
download the K2 AtoB instructions and look at the 2nd column of page 12.

73,
Don W3FPR

 -Original Message-

 All the components look right.  I guess I've got the dreaded high
 Q crystals.  I've noticed in the Elecraft archives that it is
 possible to put a capacitor at the junction of X3/X4 to ground.
 Which is the preferred method?

 Thanks.
 
  From: Don Wilhelm [EMAIL PROTECTED]
  Date: 2005/12/07 Wed AM 09:30:04 PST
  To: [EMAIL PROTECTED],
  elecraft@mailman.qth.net
  Subject: RE: [Elecraft] K2 BFO Test
 
  Ted,
 
  Yes, you should get the BFO range and frequency correct - you
 can continue
  with no extra effort, but it must be resolved eventually, and
 there is no
  time like the present to do it.
 
  Check the values of the capacitors C173 and C174, and while you
 are at it,
  check C169 too.  Additionally, check the varactors D37 and D38 for the
  correct type (1SV149 - the smaller ones) qne proper
 orientation.  Be certain
  the BFO crystals were the ones you soldered in - they are
 typically marked
  ECS D4.91 -S
 
  If you find all the above correct, you may have to pad
 Capacitors C173 and
  174.  Should that become necessary, use 47 pf in parallel with
 C174 and 120
  pf in parallel with C173.  The padder capacitors will lower the low
  frequency end more than the high frequency end of the range, so
 it should
  work for you - but do the padding only if there is nothing else
 wrong with
  the components.
 
  73,
  Don W3FPR
 


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RE: RE: [Elecraft] K2 BFO Test

[Tedd Wong]

I just added the pad capacitors to c174 and c173.  It helped but not enough.  
The high freq. is now 4917.37 and low is 4913.92 for a range of 3.45 kHz.  Is 
it possible to get new crystals from Elecraft if indeed I do have the ones with 
the higher Q?

Thanks
 
 From: Don Wilhelm [EMAIL PROTECTED]
 Date: 2005/12/07 Wed PM 01:31:31 PST
 To: [EMAIL PROTECTED],  elecraft@mailman.qth.net
 Subject: RE: RE: [Elecraft] K2 BFO Test
 
 The preferred method of padding the BFO capacitors is to maintain the ratio
 between C173 and C174 by paralleling them with capacitors.  A single
 capacitor from the junction to ground will be in parallel with the series
 combination of C173 and the varactor D38 and could make the BFO less stable
 than it should be.
 
 You are welcome to try the single capacitor solution, but do beware of the
 pitfalls.  If you would like further documentation on padding the BFO,
 download the K2 AtoB instructions and look at the 2nd column of page 12.
 
 73,
 Don W3FPR
 
  -Original Message-
 
  All the components look right.  I guess I've got the dreaded high
  Q crystals.  I've noticed in the Elecraft archives that it is
  possible to put a capacitor at the junction of X3/X4 to ground.
  Which is the preferred method?
 
  Thanks.
  
   From: Don Wilhelm [EMAIL PROTECTED]
   Date: 2005/12/07 Wed AM 09:30:04 PST
   To: [EMAIL PROTECTED],
 elecraft@mailman.qth.net
   Subject: RE: [Elecraft] K2 BFO Test
  
   Ted,
  
   Yes, you should get the BFO range and frequency correct - you
  can continue
   with no extra effort, but it must be resolved eventually, and
  there is no
   time like the present to do it.
  
   Check the values of the capacitors C173 and C174, and while you
  are at it,
   check C169 too.  Additionally, check the varactors D37 and D38 for the
   correct type (1SV149 - the smaller ones) qne proper
  orientation.  Be certain
   the BFO crystals were the ones you soldered in - they are
  typically marked
   ECS D4.91 -S
  
   If you find all the above correct, you may have to pad
  Capacitors C173 and
   174.  Should that become necessary, use 47 pf in parallel with
  C174 and 120
   pf in parallel with C173.  The padder capacitors will lower the low
   frequency end more than the high frequency end of the range, so
  it should
   work for you - but do the padding only if there is nothing else
  wrong with
   the components.
  
   73,
   Don W3FPR
  
 
 
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[Elecraft] K2 BFO Test

[wongtheo]

I am in the process of testing the BFO on page 62.  Everything tested fine up 
to this point but now I can not get the proper BFO range.  The BFO high 
frequency is 4917.56 and the BFO low frequency is 4914.26.  This provides a BFO 
range of 3.2 kHz. It appears that I can not the the BFO low frequency below 
4912.7 as specified in the manual.  I checked L33 to make sure R116 is not 
shorting any turns.  Should I troubleshoot this problem before proceding?  If 
so where else should I look.  Thanks.

Ted K6OI
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[Elecraft] K2 BFO test after adding a capacitor

[Rolf Moberg, OH6KXL]

Hello!

After few weeks building incativity due to hot summer I'm back in my 
shack. My K2 #4759 has been on the air several months. However, BFO 
lower limit frequency didn't meet the required 4912.7 kHz


Leigh, WA5ZNU sent me a mail which he had got from Gary from Elecraft. 
Gary adviced to add 1-4pF NP0-capacitor to junction of X3 and X4. I mean 
the lower junction in schematics. That is connected to L33. I added 
1.5pF NP0 capacitor on the bottom of the RF board. Other pin of 
capacitor was soldered to ground pad of X4.


BFO is now working OK. You can find the new frequencies below. Original 
frequencies are shown in the brackets.


BFO High Freq. 4917.17 kHz (4917.23 kHz) must be = 4916.3 kHz
BFO Low Freq.  4912.50 kHz (4912.95 kHz) must be = 4912.7 kHz

I'd be interested in the technical report why adding a little cap to the 
paralleel of L33 and series with parallel connected crystals lowered the 
oscillator frequency. I'm not an engineer. But I'd like to understand.


Should I make CAL FIL (and CAL PLL) again after this mod? I assume they 
are not needed.


Rolf Moberg
oh6kxl
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RE: [Elecraft] K2 BFO test after adding a capacitor

[W3FPR - Don Wilhelm]

Rolf,

Yes, re-do CAL FIL to properly reposition the filter passbands - the BFO
controls that positioning, so any change in BFO frequency will cause a
shift.

You should not need to run CAL PLL since the PLL reference oscillator has
not been changed.

Why does adding a capacitor change the frequency?  The BFO is actually a
VXO, and the frequency is controlled by changing the capacitance in the
circuit - normally that is done by changing the voltage on the varicaps, but
since your total capacitance range was slightly out of normal a small padder
capacitor needed to be added.

73,
Don W3FPR

 -Original Message-

 Hello!

 After few weeks building incativity due to hot summer I'm back in my
 shack. My K2 #4759 has been on the air several months. However, BFO
 lower limit frequency didn't meet the required 4912.7 kHz

 Leigh, WA5ZNU sent me a mail which he had got from Gary from Elecraft.
 Gary adviced to add 1-4pF NP0-capacitor to junction of X3 and X4. I mean
 the lower junction in schematics. That is connected to L33. I added
 1.5pF NP0 capacitor on the bottom of the RF board. Other pin of
 capacitor was soldered to ground pad of X4.

 BFO is now working OK. You can find the new frequencies below. Original
 frequencies are shown in the brackets.

 BFO High Freq. 4917.17 kHz (4917.23 kHz) must be = 4916.3 kHz
 BFO Low Freq.  4912.50 kHz (4912.95 kHz) must be = 4912.7 kHz

 I'd be interested in the technical report why adding a little cap to the
 paralleel of L33 and series with parallel connected crystals lowered the
 oscillator frequency. I'm not an engineer. But I'd like to understand.

 Should I make CAL FIL (and CAL PLL) again after this mod? I assume they
 are not needed.

 Rolf Moberg
 oh6kxl

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RE: [Elecraft] K2 BFO Test: BFO low freq is really low

[Ron D'Eau Claire]

Excellent catch by both you and Jim, K4ZM, who replied off line.  A flaky
input stage to the counter certainly would fit the symptoms.

Please, never be shy about speaking up on the reflector!  That's what makes
this forum so valuable.

It's been nearly four years since I built old number 1289 and I had
forgotten about that Builder's Alert.

Thanks! 

Ron AC7AC

-Original Message-



A possible cause of misreading the BFO frequency at TP2 may be due to  the
K2 
frequency counter being insensitive.
 
See Elecraft Builders Alert #21 of October 19, 2004...
 
Regards,
Bob, G3VVT



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[Elecraft] K2 BFO Test: BFO low freq is really low

[Jason Marten]

I've come to the Alignment and Test, Part II.  I think I'm having a problem 
under the BFO test.


Following the instructions, I switch to 40m, hook up the frequency counter 
to TP2, and get a reading of 4913.52.  The manual says I should get 
something between 4908 and 4918.  So far, so good.


Next, I go to the part where you determine the BFO range.  After hitting 
Band+, I get a reading of 4917.54 kHz.  The manual says you need = 4916.3, 
and it's usually between 4916--4917.  Maybe a tad high, but looks good to 
me.  After hitting Band-, I get a reading of 2456.11 kHz.  The manual says 
it must be = 4912.7 (which it most certainly is) but it is usually about 
4909--4912 (which is isn't, by a long shot).  This results in a range of 
2461.43.  The manual says it must be = 3.6 (which it is, by a lot), but 
it's typically 4--6 kHz.


It looks like I'm meeting the letter of the law based on the = and = 
requirements, but I'm nowhere near the typical ranges on the BFO low freq. 
and range.


Following this test in the manual is some info on what to do if the 
frequencies are too high or too low:


First off, I did not use a frequency counter to adjust C22 on the control 
board,   I used a separate receiver and hooked up a wire from its antenna 
jack to the 4 MHz crystal, as described in the manual.  This resulted in me 
turning C22 less than 30 degrees counter clock wise (anti clock wise).  This 
seems reasonable to me, so I don't think C22 is off by very much.  However, 
I think I might want to try using a frequency counter, to get a little more 
accuracy in calibration.  Could anybody recommend an affordable frequency 
counter?  I've never shopped around for them, so I have no clue as to the 
price, etc.


The third point mentions I might have shorted out part of L33.  Looking 
under a loupe, I did not see any evidence of a short, and in fact, I can 
slide L33 underneath R116, it doesn't appear that heating R116 affected L33.


The fourth point mentions L33 could be broken.  I put my DMM on the tiny 
leads attached to R116 and got 1.7 Ohms.  Does this sound reasonable?


The final point says to check the capacitors and diodes in the BFO circuit.  
After another quick look, this appears to be OK to my eyes.


Any help would be appreciated!


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Re: [Elecraft] K2 BFO Test: BFO low freq is really low

[W3FPR - Don Wilhelm]

Jason,

Yes, 2456 kHz IS way too low - in fact it is quite out-of -bounds - and is 
close to only half the frequency that it should be.


First thing to check is soldering, then re-check the soldering, and when you 
are finished, check soldering again.  Use the schematic to identify those 
components in the BFO area and check them carefully for good solder joints 
and proper values.


Be certain the varactor diodes are the correct type, and be certain the 
crystal the correct one and is properly soldered.  The BFO is a VXO type 
circuit, and if everything is proper, it would be very difficult if not 
impossible to pull a good crystal by 50% of its frequency.  If everything 
else is correct, you may have a bad crystal (or perhaps it is shorted at the 
solder joints by excess solder) - consider removing the crystal, cleaning up 
the solder and putting it back in.


Lastly, look for something wrong with either the counter probe or the RF 
voltage at the BFO test point.  It is possible (but not probable) that the 
voltage is high enough to properly count the frequency at the high end, but 
drops off at the low end and counts only approximately half the pulses.  If 
you have a 'scope (or build the RF probe included with your K2 kit), it 
should be able to tell you if the RF voltage is really lower at the low 
frequency end.


The calibration of the 4 MHz reference may cause reading to be off by a bit, 
but not nearly the difference you are reporting.  If you set it with another 
receiver, you are close enough for now - you can refine it later when you 
have completed the K2 and are ready to do a precise dial calibration.  I 
recommend using the most recent method of zeroing WWV and comparing the BFO 
and VCO frequencies (previously known as the N6KR method).  Details are on 
the Elecraft website and can also be found in the K2 dial calibration 
article on my website www.qsl.net/w3fpr.


73,
Don W3FPR


- Original Message - 
From: Jason Marten [EMAIL PROTECTED]


I've come to the Alignment and Test, Part II.  I think I'm having a 
problem under the BFO test.


Following the instructions, I switch to 40m, hook up the frequency counter 
to TP2, and get a reading of 4913.52.  The manual says I should get 
something between 4908 and 4918.  So far, so good.


Next, I go to the part where you determine the BFO range.  After hitting 
Band+, I get a reading of 4917.54 kHz.  The manual says you need = 
4916.3, and it's usually between 4916--4917.  Maybe a tad high, but looks 
good to me.  After hitting Band-, I get a reading of 2456.11 kHz.  The 
manual says it must be = 4912.7 (which it most certainly is) but it is 
usually about 4909--4912 (which is isn't, by a long shot).  This results 
in a range of 2461.43.  The manual says it must be = 3.6 (which it is, by 
a lot), but it's typically 4--6 kHz.


It looks like I'm meeting the letter of the law based on the = and = 
requirements, but I'm nowhere near the typical ranges on the BFO low freq. 
and range.


Following this test in the manual is some info on what to do if the 
frequencies are too high or too low:


First off, I did not use a frequency counter to adjust C22 on the control 
board,   I used a separate receiver and hooked up a wire from its antenna 
jack to the 4 MHz crystal, as described in the manual.  This resulted in 
me turning C22 less than 30 degrees counter clock wise (anti clock wise). 
This seems reasonable to me, so I don't think C22 is off by very much. 
However, I think I might want to try using a frequency counter, to get a 
little more accuracy in calibration.  Could anybody recommend an 
affordable frequency counter?  I've never shopped around for them, so I 
have no clue as to the price, etc.


The third point mentions I might have shorted out part of L33.  Looking 
under a loupe, I did not see any evidence of a short, and in fact, I can 
slide L33 underneath R116, it doesn't appear that heating R116 affected 
L33.


The fourth point mentions L33 could be broken.  I put my DMM on the tiny 
leads attached to R116 and got 1.7 Ohms.  Does this sound reasonable?


The final point says to check the capacitors and diodes in the BFO 
circuit.  After another quick look, this appears to be OK to my eyes.


Any help would be appreciated!


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RE: [Elecraft] K2 BFO Test: BFO low freq is really low

[Ron D'Eau Claire]

It looks like the counter is only registering half the frequency and it's
really at 4912 kHz. 

I don't think it's physically possible for the BFO to oscillate down there.
Certainly not under crystal control. C22 won't vary your counter time base
enough to cause anything like that sort of error. You can confirm that he
counter is working by simply going back to the other end of the range where
you read 4917.54 kHz and confirm it still works. 

I'm really stumped to suggest where it might be happening though. I'd say
the counter but if you get a good reading at 4917.54, I don't see how that
could be it.  

Ron AC7AC

-Original Message-
I've come to the Alignment and Test, Part II.  I think I'm having a problem 
under the BFO test.

Following the instructions, I switch to 40m, hook up the frequency counter 
to TP2, and get a reading of 4913.52.  The manual says I should get 
something between 4908 and 4918.  So far, so good.

Next, I go to the part where you determine the BFO range.  After hitting 
Band+, I get a reading of 4917.54 kHz.  The manual says you need =
Band+4916.3,
and it's usually between 4916--4917.  Maybe a tad high, but looks good to 
me.  After hitting Band-, I get a reading of 2456.11 kHz.  The manual says 
it must be = 4912.7 (which it most certainly is) but it is usually about 
4909--4912 (which is isn't, by a long shot).  This results in a range of 
2461.43.  The manual says it must be = 3.6 (which it is, by a lot), but 
it's typically 4--6 kHz.

It looks like I'm meeting the letter of the law based on the = and = 
requirements, but I'm nowhere near the typical ranges on the BFO low freq. 
and range.

Following this test in the manual is some info on what to do if the 
frequencies are too high or too low:

First off, I did not use a frequency counter to adjust C22 on the control 
board,   I used a separate receiver and hooked up a wire from its antenna 
jack to the 4 MHz crystal, as described in the manual.  This resulted in me 
turning C22 less than 30 degrees counter clock wise (anti clock wise).  This

seems reasonable to me, so I don't think C22 is off by very much.  However, 
I think I might want to try using a frequency counter, to get a little more 
accuracy in calibration.  Could anybody recommend an affordable frequency 
counter?  I've never shopped around for them, so I have no clue as to the 
price, etc.

The third point mentions I might have shorted out part of L33.  Looking 
under a loupe, I did not see any evidence of a short, and in fact, I can 
slide L33 underneath R116, it doesn't appear that heating R116 affected L33.

The fourth point mentions L33 could be broken.  I put my DMM on the tiny 
leads attached to R116 and got 1.7 Ohms.  Does this sound reasonable?

The final point says to check the capacitors and diodes in the BFO circuit.

After another quick look, this appears to be OK to my eyes.

Any help would be appreciated!


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