From: "Ken, WA2LBI" 
Subject: Re: [drakelist] R4A AGC inop.


George,

A few questions:
* Did you verify that the transistor is good? It might be loose as the result of
somebody's previous attempt to repair the same problem. I have had bad ones.
* When you turn the function switch to standby does the S meter rise to 60 and
is the receiver muted?
* While monitoring the AVC/AGC line test point does it change as the function
switch is moved from ON to Standby?
* Have you verified that the bias supply voltage is present and correct?
* Does bias voltage appear at the high side of the RF gain control?
* Have you checked for continuity and proper resistor values in the vicinity of
the RF gain control?

Ken, WA2LBI

Quoting George :

>
> Hi all
> went through it and found the transistor on the agc board was loose
> resoldered and went to readjust the bias and s meter. I turned the
> rf gain fully counterclockwise and it would not move the s meter to 60 like
> it did before and was bouncing around. still no agc action.....
>
> George ne2i
>
>
>
> ----- Original Message -----
> From: "Ken, WA2LBI" 
> To: "George" 
> Cc: 
> Sent: Friday, April 09, 2004 4:04 AM
> Subject: Re: [drakelist] R4A AGC inop.
>
>
> >
> > George,
> >
> > Since this receiver is new to you don't overlook the possibility of
> MULTIPLE
> > problems. I serviced a R-4B last year that had similar symptoms, among
> others,
> > to yours and it turned out to have several bad tubes and resistors. Of
> course I
> > had swapped tubes in order to isolate the problem but I was actually
> swapping
> > one bad tube for another! Talk about chasing your tail!
> >
> > Have you checked all the voltages and resistances against the
> corresponding
> > charts in the manual? That is a good place to start with a new rig with an
> > unknown history.
> >
> > Keep us posted on your progress.
> >
> > Ken, WA2LBI
> >
> > Quoting Garey Barrell :
> >
> > >
> > > George -
> > >
> > > OK..
> > >
> > > Measure the voltage at TP-2 (on top of the chassis, just in
> > > front of the Passband tuner.)  Should measure -1.35 volts
> > > with the the Preselector detuned on any band.
> > >
> > > Have you tried both Fast and Slow AVC?  If no AVC in either
> > > position, try swapping the Calibrator tube, 12BA6, with
> > > either of the IF tubes, V4 or V5.  Something is loading the
> > > AVC line.  If this doesn't help, try swapping the RF Amp, V1
> > > with another 12BZ6.
> > >
> > > Beyond this, you'll have to find what is either loading or
> > > shorting the AVC line.  Possibly one of the grid resistors
> > > of V1, V4 or V5 cracked or open.  They can go up in value
> > > considerably without affecting the AVC, so unless they are
> > > open, look elsewhere.
> > >
> > > Let us know what you find.
> > >
> > > 73, Garey - K4OAH
> > >
> > >
> > >
> > > George wrote:
> > >
> > > > To add to that it is an 11 tube model (no 12av6)
> > > >
> > > > George NE2I
> > > >   ----- Original Message -----
> > > >   From: George
> > > >   To: drakelist{at}www.zerobeat.net
> > > >   Sent: Thursday, April 08, 2004 9:00 PM
> > > >   Subject: [drakelist] R4A AGC inop.
> > > >
> > > >
> > > >   Just bought an r4a and it seems like the agc is not
working at all
> > > >   I have to ride the rf gain or I get way too much audio and
> distortion
> > > >   It has good sensitivity and is spot on frequency wise.
> > > >
> > > >   Also when I select NB or cal the s-meter pegs and I
dont get any
> audio.
> > > >
> > > >   Thanks
> > > >   George NE2I
> > > >
> > > >
> > > ----------------------------------------------------------------------
> > > Submissions:        drakelist{at}www.zerobeat.net
> > > Subscribe:          majordomo{at}www.zerobeat.net - subscribe
drakelist in
> body
> > > Unsubscribe:        majordomo{at}www.zerobeat.net - unsubscribe drakelist
> in
> > > body
> > > Hopelessly Lost:    majordomo{at}www.zerobeat.net - help in
body of message

---