Re: [time-nuts] question about HP 5601a harmonic generator

2017-12-25 Thread Morris Odell 
Hi,

Fortunately I have not had this problem but I did have to deal with a destroyed 
SRD in a HP 5110A  synthesizer driver a few years ago. The SRD in that device 
is maintained at an elevated temperature in a little oven and as a result of a 
thermostat failure it was reduced to a charred blob. With no possibility of 
finding an original  replacement I set the harmonic generator module up on the 
bench ( no easy feat!) and tried a range of different diodes to see if any of 
them would work. After a lot of experimentation I finally hit on a power 
varactor diode that was the final frequency multiplier in a junked cellphone 
transmitter from the original analog FM system that was eventually replaced 
with the current digital one. That diode was made by National Panasonic and is 
a gold plated stud mounted device. I had to fiddle around to fit it in but the 
5110A has not missed a beat since. Of course, in the 5110A it does operate at a 
much lower frequency than the 5061A, but it's original use was i
 n the upper VHF range I think.

If you can't find a replacement you might have to resort to similar 
experimentation .

Morris



> May I know if anyone knows the part number or the specification of the 
> step recovery diode in the harmonic generator for the old HP 5601A 
> cesium frequency standard?
> 


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[time-nuts] question about HP 5601a harmonic generator

2017-12-25 Thread cdelect 
When working on the A4 assy. the ONLY adjustments you should make are:

- Cavity frequency, unscrew locking ring and while looking at the A7 J1
signal or 2nd harmonic reading adjust for max and then lock down.

- Attenuator, Unlock with allen, adjust for same, usually pulled all the
way out. Remember to lock.

-S5 the one by the attenuator, only needed if tube swapped but if you
adjust make sure the peak does not slip when you tighten the locknut.

- the top pot, adjust for the same.

- If you adjust any of the other locknutted plungers you will NEVER get
back to where you need to be

Cheers,


Corby

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Re: [time-nuts] question about HP 5601a harmonic generator

2017-12-24 Thread paul swed 
Kejia
Rick gave you some very good information. I have to agree that the SRDs are
pretty tough from my experience. I have several 5061s. But they do need the
bias and the RF at the level indicated in the manual. Not to much not to
little.
There is also a RF attenuator knob on the multiplier. So pretty easy to
mess it up. Seems that knobs are also a favored choice to adjust. Try to
back everything out like the manual says and see if you can get things
going.
If the diode is really bad your only hope is a bad 5061 on ebay. Many have
bad tubes and are parts units. But they still seem to get a pretty high
price.
Good luck
Paul
WB8TSL

On Sun, Dec 24, 2017 at 1:42 PM, Richard (Rick) Karlquist <
rich...@karlquist.com> wrote:

> I extensively studied the 5061 harmonic generator when I
> was designing the harmonic generator in the 5071A.
> We are now going on 30 years since that work.  The diode
> had some HP part number.  Even if you knew this part
> number, you would need to have the Part Information Report
> microfiche that gave the vendor part number.  The
> chances of this diode still being available are very slim.
> So you are not going to get an exact replacement, except
> by cannibalizing another 5061 harmonic generator assembly,
> assuming it doesn't also have a bad diode.  As far as
> replacing it with a different diode, that too would be
> questionable.  SRD's have magic unspecified parameters
> when it comes to what they do in a circuit.  The 5061
> generator in particular has extremely high efficiency
> due to its unique design.  It was designed by a Korean
> professor named Soon Choi (IIRC) who spent a summer
> at HP.  He left no known documentation as to how the
> design works, or how to specify the SRD.
>
> After a long period of study, I concluded that I was
> never going to match the efficiency in any simple
> circuit.  The diode mounted directly in the waveguide
> is the magic.  Fortunately, by that time, we could use
> a phase locked DRO and get around this problem.  Len
> Cutler in his usual style criticized me for "taking the
> easy way out", but he eventually came around to my
> way of thinking.
>
> I will give you a little hope.  The harmonic generator
> consists of a bunch of silver plated parts that are
> supposed to fit together and achieve electrical conductivity.
> After many years, the silver and tarnish and upset the
> electrical conductivity.  You might try disassembling
> the diode mount and cleaning up everything.  After
> you reassemble it, you might have good news.
>
> I will say that I have never heard of an SRD failing,
> and as you say, it looks good at DC.  What possible
> failure mechanism could selectively make the diode
> stop generating harmonics but other wise be OK at DC?
> Somehow let the pixie dust escape without letting the
> smoke escape.  Seems unlikely.
>
> Also check the drive circuitry.  SRD's need tricky components
> to make them "step" correctly.  Again, poor grounding due
> to corrosion could spoil the harmonic generation.
>
> Rick Karlquist N6RK
> Member of the 5071A design team
>
>
> On 12/24/2017 3:54 AM, Kejia Lee wrote:
>
>> Dear All,
>>
>> Happy Christmas!
>>
>> May I know if anyone knows the part number or the specification of the
>> step
>> recovery diode in the harmonic
>> generator for the old HP 5601A cesium frequency standard?
>>
>> I recently received this toy. The cesium tube seems to be OK, and I had
>> located the problem being
>> no 9GHz from the waveguide. I checked the diode, the DC properties seems
>> to
>> be OK, but just
>> can not generate frequency comb any more. I really hope I can repair it as
>> a personal new-year gift.
>>
>> I will be really appreciated, if you had any suggestions.
>>
>> Best regards,
>>
>> K.
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>> ailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>>
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Re: [time-nuts] question about HP 5601a harmonic generator

2017-12-24 Thread Kejia Lee 
Dear Richard,

Very nice to hear from you, and thank you a lot for the help!
Indeed, I have cleaned the erosion still not working.

I am trying to now* remeasure the break voltage of the diode*.
I suspect that the doping get diffused in the isolation layer after age,
which make it a good diode, but with different parameter for the step
recovery.

>From what I see in the circuit, I understand that *I need to tune the *
*resonance at a given frequency to have higher voltage to make sure *
*the diode reversely discharged*. I noted the tuning is very tricky, as
the waveguide assembly is also a part of the resonance circuit.

*Do you have a internal dimension of the assembly*, that will help speed up
with the EM calculation to understand which screw for what.

Best regards,

Kj

2017-12-25 2:42 GMT+08:00 Richard (Rick) Karlquist :

> I extensively studied the 5061 harmonic generator when I
> was designing the harmonic generator in the 5071A.
> We are now going on 30 years since that work.  The diode
> had some HP part number.  Even if you knew this part
> number, you would need to have the Part Information Report
> microfiche that gave the vendor part number.  The
> chances of this diode still being available are very slim.
> So you are not going to get an exact replacement, except
> by cannibalizing another 5061 harmonic generator assembly,
> assuming it doesn't also have a bad diode.  As far as
> replacing it with a different diode, that too would be
> questionable.  SRD's have magic unspecified parameters
> when it comes to what they do in a circuit.  The 5061
> generator in particular has extremely high efficiency
> due to its unique design.  It was designed by a Korean
> professor named Soon Choi (IIRC) who spent a summer
> at HP.  He left no known documentation as to how the
> design works, or how to specify the SRD.
>
> After a long period of study, I concluded that I was
> never going to match the efficiency in any simple
> circuit.  The diode mounted directly in the waveguide
> is the magic.  Fortunately, by that time, we could use
> a phase locked DRO and get around this problem.  Len
> Cutler in his usual style criticized me for "taking the
> easy way out", but he eventually came around to my
> way of thinking.
>
> I will give you a little hope.  The harmonic generator
> consists of a bunch of silver plated parts that are
> supposed to fit together and achieve electrical conductivity.
> After many years, the silver and tarnish and upset the
> electrical conductivity.  You might try disassembling
> the diode mount and cleaning up everything.  After
> you reassemble it, you might have good news.
>
> I will say that I have never heard of an SRD failing,
> and as you say, it looks good at DC.  What possible
> failure mechanism could selectively make the diode
> stop generating harmonics but other wise be OK at DC?
> Somehow let the pixie dust escape without letting the
> smoke escape.  Seems unlikely.
>
> Also check the drive circuitry.  SRD's need tricky components
> to make them "step" correctly.  Again, poor grounding due
> to corrosion could spoil the harmonic generation.
>
> Rick Karlquist N6RK
> Member of the 5071A design team
>
>
> On 12/24/2017 3:54 AM, Kejia Lee wrote:
>
>> Dear All,
>>
>> Happy Christmas!
>>
>> May I know if anyone knows the part number or the specification of the
>> step
>> recovery diode in the harmonic
>> generator for the old HP 5601A cesium frequency standard?
>>
>> I recently received this toy. The cesium tube seems to be OK, and I had
>> located the problem being
>> no 9GHz from the waveguide. I checked the diode, the DC properties seems
>> to
>> be OK, but just
>> can not generate frequency comb any more. I really hope I can repair it as
>> a personal new-year gift.
>>
>> I will be really appreciated, if you had any suggestions.
>>
>> Best regards,
>>
>> K.
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>> To unsubscribe, go to https://www.febo.com/cgi-bin/m
>> ailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>>
>>
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Re: [time-nuts] question about HP 5601a harmonic generator

2017-12-24 Thread Richard (Rick) Karlquist 

I extensively studied the 5061 harmonic generator when I
was designing the harmonic generator in the 5071A.
We are now going on 30 years since that work.  The diode
had some HP part number.  Even if you knew this part
number, you would need to have the Part Information Report
microfiche that gave the vendor part number.  The
chances of this diode still being available are very slim.
So you are not going to get an exact replacement, except
by cannibalizing another 5061 harmonic generator assembly,
assuming it doesn't also have a bad diode.  As far as
replacing it with a different diode, that too would be
questionable.  SRD's have magic unspecified parameters
when it comes to what they do in a circuit.  The 5061
generator in particular has extremely high efficiency
due to its unique design.  It was designed by a Korean
professor named Soon Choi (IIRC) who spent a summer
at HP.  He left no known documentation as to how the
design works, or how to specify the SRD.

After a long period of study, I concluded that I was
never going to match the efficiency in any simple
circuit.  The diode mounted directly in the waveguide
is the magic.  Fortunately, by that time, we could use
a phase locked DRO and get around this problem.  Len
Cutler in his usual style criticized me for "taking the
easy way out", but he eventually came around to my
way of thinking.

I will give you a little hope.  The harmonic generator
consists of a bunch of silver plated parts that are
supposed to fit together and achieve electrical conductivity.
After many years, the silver and tarnish and upset the
electrical conductivity.  You might try disassembling
the diode mount and cleaning up everything.  After
you reassemble it, you might have good news.

I will say that I have never heard of an SRD failing,
and as you say, it looks good at DC.  What possible
failure mechanism could selectively make the diode
stop generating harmonics but other wise be OK at DC?
Somehow let the pixie dust escape without letting the
smoke escape.  Seems unlikely.

Also check the drive circuitry.  SRD's need tricky components
to make them "step" correctly.  Again, poor grounding due
to corrosion could spoil the harmonic generation.

Rick Karlquist N6RK
Member of the 5071A design team

On 12/24/2017 3:54 AM, Kejia Lee wrote:

Dear All,

Happy Christmas!

May I know if anyone knows the part number or the specification of the step
recovery diode in the harmonic
generator for the old HP 5601A cesium frequency standard?

I recently received this toy. The cesium tube seems to be OK, and I had
located the problem being
no 9GHz from the waveguide. I checked the diode, the DC properties seems to
be OK, but just
can not generate frequency comb any more. I really hope I can repair it as
a personal new-year gift.

I will be really appreciated, if you had any suggestions.

Best regards,

K.
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[time-nuts] question about HP 5601a harmonic generator

2017-12-24 Thread Kejia Lee 
Dear All,

Happy Christmas!

May I know if anyone knows the part number or the specification of the step
recovery diode in the harmonic
generator for the old HP 5601A cesium frequency standard?

I recently received this toy. The cesium tube seems to be OK, and I had
located the problem being
no 9GHz from the waveguide. I checked the diode, the DC properties seems to
be OK, but just
can not generate frequency comb any more. I really hope I can repair it as
a personal new-year gift.

I will be really appreciated, if you had any suggestions.

Best regards,

K.
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