Re: [Drakelist] R-4C Audio Problem - RESOLVED!

[Bill Jackson]

Thanks to Garey and his documentation CD, my birdie problem is resolved!  I was
able to determine that somewhere in one of my receiver's previous lives a
capacitor was added across R83 on the audio board.  This provided a feedback
loop which caused the audio board to oscillate at approximately 330 KHz.  This
waveform was clearly visible on the audio output transistor using a scope.  It
was also backfeeding on the +14 volt buss to the crystal calibrator board which
modulated the crystal calibrator output, causing the birdies in the passband of
the receiver.  Adjusting the volume control changed the frequency of the
fundamental oscillation in the audio amp just enough to change the frequencies
of the birdies in the passband.

My receiver is now working fine and will be taking its place on my operating
table shortly.  Without Garey's documentation CD in hand, it would have been a
long and tedious search for that capacitor.

Thanks again to all!

73 de Bill, K9RZ


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Re: [Drakelist] Cleaned the TR-4

[Garey Barrell]

Richard -

The S-Meter is Zero'd with the cleverly disguised ZERO control on the 
right side of the chassis.!!  :-)


Disconnect antenna, detune RF TUNE control, and adjust ZERO control for 
S1 on the meter.  There is no S0 on Drake meters!


73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 4-B, C-Line&  TR-4/C Service Supplement CDs



Richard Palmer wrote:


There is on thing that is not spelled out. Zeroing the meter. I 
cleaned all the pots and when I went to zero the meter I found nothing 
to help me determine the proper setting. So any help there is 
appreciated.


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Re: [Drakelist] Cleaned the TR-4

[Richard Palmer]

Gary,

Since I cleaned it I knew where it was. I noticed that the zero adjust 
affected the meter's reading of the bias also ... so I wanted to get it 
set correctly.


Thanks for your help,
Richard Palmer

Garey Barrell wrote:

Richard -

The S-Meter is Zero'd with the cleverly disguised ZERO control on the 
right side of the chassis.!!  :-)


Disconnect antenna, detune RF TUNE control, and adjust ZERO control 
for S1 on the meter.  There is no S0 on Drake meters!


73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 4-B, C-Line&  TR-4/C Service Supplement CDs



Richard Palmer wrote:


There is on thing that is not spelled out. Zeroing the meter. I 
cleaned all the pots and when I went to zero the meter I found 
nothing to help me determine the proper setting. So any help there is 
appreciated.


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--
The law, in its majestic equality, forbids the rich as well as the poor to 
sleep under bridges, to beg in the streets, and to steal bread.   - Anatole 
France


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Re: [Drakelist] T4XB No +250V AND blown Filament Fuse

[Paul Gerhardt]

OK still troubleshooting but found 2 more clues

I pulled all the tubes and the AC4 power resistor R3 in the 250V line is now
cool to touch and V is 260V with NO tubes in.
When OA2 is in place (only OA2) R3 is too hot to touch and V drops about
12V.

2nd Clue I finally found what smoked in the chassis.  It was hiding under a
switch shaft in the RF compartment.  The 'smoker' was R30 the 68 ohm 1/2
watt resistor on V5 (final)

So I think maybe the tube had a grid to fil short and took out both
circuits.

I am still not getting a spot signal.  R3 is still too hot when OA2 is 'IN'

OA2 is blue not shure otherwise if it is good?  Problem may be on the 150 V
line as that powers the VFO (I think).

Still have the tubes out.

Paul K3PG in 'snowy' MD
pix on http://pgerhardt.blogspot.com




On Thu, Feb 4, 2010 at 11:31 AM, Paul Gerhardt  wrote:

> Turned on my Working T4Xb and smoke came out the bottom of the rig which I
> can't see for some reason.  The filimant fuse (8A pigtail lead fuse near the
> 3 big power resistors) is open so replaced that, then no 250 V B+ and found
> R3 1K 5 watt resistor to be open.  Both of these were 'effect' and not cause
> (I suspect).  I changed R3 and got 150V and R3 is hot.  Unhooked the yellow
> 250V wire to the rig and V is good about 270V.  Turned power OFF and
> measured Resistance on yellow wire and it is low only about 150 ohms.  Last
> thing is always suspect and for this the last thing I did a few days ago was
> install some used FleaBay finals which worked ok it seemed but were very
> weak only about 60-70 watts out (maybe one was not working?)  Put the bright
> light on the bottom and compared to photo I took before and fail to 'see'
> any burned parts on the bottom but there was smoke and I think it was from a
> hot wire and not a componet.  Will probably change the finals back to the
> 'other' weak ones that were at least putting out 120W into the Cantenna and
> see what is pulling the 250V B+ line down.
> Any ideas on this one?
>
> 73
> Paul
>
>


>
>
> --
> Paul Gerhardt
> K3PG
> http://pgerhardt.blogspot.com
> QRP ARCI 6674
> FP 274
>
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Re: [Drakelist] T4XB No +250V AND blown Filament Fuse

[Garey Barrell]

Paul -

OK.  See below.

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 4-B, C-Line&  TR-4/C Service Supplement CDs



Paul Gerhardt wrote:

OK still troubleshooting but found 2 more clues
I pulled all the tubes and the AC4 power resistor R3 in the 250V line 
is now cool to touch and V is 260V with NO tubes in.
When OA2 is in place (only OA2) R3 is too hot to touch and V drops 
about 12V.


The 0A2 will glow blue when it is working, and will have +150V across 
it.  12V drop across R3 is a little high, but is about 1.5W dissipation, 
assuming it is 100 ohms.
2nd Clue I finally found what smoked in the chassis.  It was hiding 
under a switch shaft in the RF compartment.  The 'smoker' was R30 the 
68 ohm 1/2 watt resistor on V5 (final)
So I think maybe the tube had a grid to fil short and took out both 
circuits.


I think that's where we started!  :-)
I am still not getting a spot signal.  R3 is still too hot when OA2 is 
'IN'


SPOT will not be present with V8 out of the socket.

Again, 12 V drop across R3 is ok, only 1.5W, and if the 0A2 is blue, 
it's regulating.  The +150 bus drives the PTO, BAND OSC and the screen 
of the PreMixer, along with V1, V2 Screen and V3 screen.  The PTO supply 
should have about 11 V on it, at the "low" end of R64, 6k @ 5W.


OA2 is blue not shure otherwise if it is good?  Problem may be on the 
150 V line as that powers the VFO (I think).



Still have the tubes out.
Paul K3PG in 'snowy' MD
pix on http://pgerhardt.blogspot.com 



On Thu, Feb 4, 2010 at 11:31 AM, Paul Gerhardt > wrote:


Turned on my Working T4Xb and smoke came out the bottom of the rig
which I can't see for some reason.  The filimant fuse (8A pigtail
lead fuse near the 3 big power resistors) is open so replaced
that, then no 250 V B+ and found R3 1K 5 watt resistor to be
open.  Both of these were 'effect' and not cause (I suspect).  I
changed R3 and got 150V and R3 is hot.  Unhooked the yellow 250V
wire to the rig and V is good about 270V.  Turned power OFF and
measured Resistance on yellow wire and it is low only about 150
ohms.  Last thing is always suspect and for this the last thing I
did a few days ago was install some used FleaBay finals which
worked ok it seemed but were very weak only about 60-70 watts out
(maybe one was not working?)  Put the bright light on the bottom
and compared to photo I took before and fail to 'see' any burned
parts on the bottom but there was smoke and I think it was from a
hot wire and not a componet.  Will probably change the finals back
to the 'other' weak ones that were at least putting out 120W into
the Cantenna and see what is pulling the 250V B+ line down.
Any ideas on this one?
73
Paul



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