[MRCA] Re: Angry Nine Woes

[Radio Station KW1I]

Thanks Dennis for the review of that fix.  I printed out a copy and placed 
it in my GRC-9 tech pub.

Good luck Al!

Dale
KW1I

----- Original Message ----- 
From: <W7QHO at aol.com>
To: <al at ar88.net>; <boatanchors at theporch.com>; <milsurplus at mailman.qth.net>; 
<mrca at mailman.qth.net>
Sent: Wednesday, August 01, 2007 7:38 PM
Subject: [MRCA] Re: Angry Nine Woes



In a message dated 8/1/07 4:09:38 PM, al at ar88.net writes:


> I'm back to working on an AN/GRC-9 that's been lying around here for too
> long. No TX output as there is not enough grid drive to the 2E22 to
> actuate the safety relay that turns on the screen grid. DC on the PA
> grid (pin 5 of the test connector) is about minus 12-15 volts. It's
> supposed to be -60. All tubes have been checked. Voltage and
> resistance on the tube pins checks OK. Grid drive to the driver tube is
> maybe 10% low. Tuned circuits seem to peak. Same problem on all three
> bands crystal or MO. (This is giving me /deja vu/. I had the same sort
> of trouble with a 2-meter Gonset that I gave up on. I'm a receiver
> guy.) Any suggestions?
>
>
Al, et-al,

GRC-9 drive problems; ah, yes...   Following information sent around last
fall.

"Speaking of GRC-9s, there is a capacitor in these sets that requires a 
major
disassembly effort to replace.   C-114 bypasses the cold ends of the PA
driver tuned circuits and is buried inside the can (T-104) that houses these 
coils.
  Leakage is manifested in low grid bias and hence improper biasing of the
2E22 suppressor grid when operating in the Phone mode.   This problem has
surfaced in four different rigs out here in the past year.

See ER #118 for a description of just how hard it is to replace this
component.   In response to this I've come up with a considerably less 
painful
solution as outlined below.   Implemented in three different sets so far 
with
excellent results.   The mod essentially involves grounding out the failed 
component
and shunt feeding the 2E22 grid.

By removing the variable cap assembly it is possible to reach the point 
where
the lead coming out of the can from Point 3 on the circuit diagram connects
to the wiper on "S101H Sect 4 FR". There are two blue wires coming off this
point too, one running over to pin 5 on the metering socket and the other to
R106. Cut the two blue wires loose and then GROUND the lead coming out of 
the
can from Point 3 where it connects to switch wiper, see above. In cutting 
the
blue wires snip off so as to give yourself as much lead length coming out of
the cable they run into as possible, see below.

Next, remove the short wire running from pin 3 (grid) on the 2E22 socket 
over
to the adjacent switch section and replace this connection with a .001 mica.
Connect the two blue wires (see above) through a small RF choke to pin 3 on
the 2E22. Bypass the cold end of the choke (where the blue wires are
connected) through a .01 cap to ground. Rather than leaving this end of the 
choke
dangling I anchored the wire lead through a small hole drilled through one 
side of
the fiber core of adjacent L101. (Picture available on request.)

Tight quarters here, lots of hemostat work and a bit of cussing too, but 
MUCH
easier than getting inside T104. No room for a full size 2.5 mh RF grid
choke but found a miniature version that worked FB. Inductance here probably 
not
too critical. Check carefully to make sure nothing shorts when the back
section is folded up in place. I had to shorten up one of the screws that 
holds
the interconnecting cable socket in place to prevent interference."

hope this works for you.

Dennis D. W7QHO
Glendale, CA



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