[Premium-Rx] Plessey PSR-2282A Troubleshooting

[thoyer]

Short update:

I didn't find any shorted tantalums and all of the voltages are good. Now
that doesn't mean some of the tantalums are not leaky but for now I forge
ahead.

The RF Filter module (B) has most of the reed relays inoperable. I tested
each one and 80% don't work. It looks like at one point someone had changed
out a few and even those don't work. I'll need to revisit this section
later.

For now I bypassed that module and fed an RF signal into module A. If I pump
in a high level signal 0.5mv I can hear the signal and the frequency seems
to be spot on.

Looks like an issue in the RF gain circuit where the multiplexer on the
front panel board is not selecting the RF gain pot at all. There seems to be
a logic issue - probably a bad IC somewhere. I checked the 4 to 16 line
decoder that operates the RF gain mux and while the inputs to the decoder
seem valid, none of the outputs respond to the input changes. There is some
inhibit logic which latches the decoder input to the output and that appears
to have an issue. I need to spend some more time there......

But one thing I have come across is that the documentation I have is for a
BFO that uses a pot and the unit I have has an encoder for the BFO
adjustment. Would anyone have the correct schematic for the front panel with
the encoder?

Thanks, 

Tom


-----Original Message-----
From: Heinz Breuer [mailto:dh2fa at me.com] 
Sent: Monday, October 07, 2019 10:55 AM
To: Thomas Hoyer
Subject: Re: [Premium-Rx] Plessey PSR-2282A Troubleshooting

Hello Tom,
I found the usual shorted tantalum capacitors in my Plessey 2250 and 2282. 
vy 73 Heinz DH2FA, KM5VT


Von meinem iPhone gesendet

> Am 07.10.2019 um 16:48 schrieb Thomas Hoyer via Premium-Rx
<premium-rx at mailman.qth.net>:
> 
> Have one of these on the bench now. All front buttons seem to work, tuning
works but I have no response to an RF input - only slight audio noise with
volume all the way up.
> All fault LEDs are on indictating no faults present.
> Looking for some ideas on where to start from thos ethat have been there,
done that. There may be an area prone to failure?
> TomW3TA
> ______________________________________________________________
> Premium-Rx mailing list
> Home: http://mailman.qth.net/mailman/listinfo/premium-rx
> Help Page: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Premium-Rx at mailman.qth.net Help Contact eMail:  
> radio at 8zo.com Home Page:  http://www.premium-rx.org/