From: Garey Barrell 
Subject: Re: [drakelist] TR7 Display problem


Garey Barrell  made an utterence to the drakelist gang
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Bud -

The 10T and 10R voltages should be ~10R and ~0T in receive, and reverse 
in transmit.   There are transistor drivers for these voltages on the 
Transmit Exciter board.  Q306 is the 10T driver and Q307 is the 10R 
driver.  These switches double as "fuses" since any short on either 
line, even momentary, will blow them.  From your measurements, Q307 is 
open.  Whatever destroyed it may or may not have been corrected by your 
earlier repair.

This will have to be resolved before anything else is done.

You can check the counter by switching to EXT and putting an HT near the 
input lead.

There are two VCOs, one 160 through 20 and the other is for 15 and 
10M.   Normally, with the Fixed Rcv button IN to unlock the VCOs, the 
counter should rise and wander around 17 MHz with Bandswitch on any 
position up to 20M.  On the 15 and 10M positions, it should settle and 
wander around 32 MHz.

3.5V for the "5V" line on the Power Supply board is normal.   It's used 
only for biasing the PIN diode switches.

73, Garey - K4OAH
Atlanta

Drake C-Line Service Manual
http://hr99.home.mindspring.com/R-4C_Servicez/>



sebdesn wrote:

>"sebdesn"  made an utterence to
the drakelist gang
>----------------------------------------------------------------------
>  I have a TR7 that on powerup reads 96670.0 and then drifts down to 96625
>after a few minutes. Tuning knob does not change it. Band switch does not
>change it except on 15 and 10 meters it goes to 9590.Up, down, store,and
>both fixed are out.aux program is on norm and does not change anything,
>counter is on norm. Checked +10v and +5v on parent board as ok. In rcv +10T
>is .386v and +10R is 0v.
> Ps board  26v dc reg is 23.2v. The -5v dc out of the power supply board
>is -3.5v. Control voltages are 3.8 6.5 4.4 5.3 3.8v .
>About 10 years ago the thing would power up at (I think)37XXX and hunt.
>Talked to Drake and they said check a resistor  on ps board. Did, and it was
>smoked and replaced it.Still did not play, was busy and put it on shelf till
>now.
>  Any direction would be appreciated.
>
>Also would like to thank Peter VE3AX  for his magnum opus on changing of the
>pin diodes in the TR7. Just did that on my other one,worked great.
>
>Bud  WØHG
>
>  
>
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