[Premium-Rx] Help request on a particular WJ-8718A/MFP

[Mark Donaldson]

Paolo,
 
As with anything electronic that needs to be troubleshot, get a manual and start with the power supply. I have lost count of how many times the fix was as simple as fixing a faulty regulator or shorted cap in the power supply. If you do not have a manual already I believe Steve Pappin has one on his site for download.
 
73s
 
Mark WA1QHQ

--- On Thu, 8/2/12, pviappiani at tin.it <pviappiani at tin.it> wrote:


From: pviappiani at tin.it <pviappiani at tin.it>
Subject: [Premium-Rx] Help request on a particular WJ-8718A/MFP
To: premium-rx at mailman.qth.net
Date: Thursday, August 2, 2012, 5:46 AM



August 02, 2012

Hi all:
My name is Paolo and I'm from La Spezia, Italy. 
Recently I acquired a (rare?) Watkins-Johnson WJ-8718A/NAV/MFP (S/N 3332) receiver, not working.
It was missing of the Power Switch (S1) and of the USB-LSB Filter Cards but it is very clean and it seems in good overall conditions; it is provided with both the 1-Hz option (8-digit frequency display) and the 10-Hz BFO option.
I replaced the power switch and I fired up the radio, but it doesn't work yet: after startup all the numerical displays of the front panel indicate "0" and all the pushbutton red LED's light up, but there is no effect when pushing any of the buttons or when turning the tuning knob. 
Every control is inoperative and the three "fault" LED's in the front panel remain always lit. 
Any advice on this general fault or about where I can start troubleshooting? 
Maybe some experienced friend can help me!

Further details:
This radio is provided with the following boards in the Interface and Synthesizer sections:
IF Interface (MFP-A3): Card 794308;
Synthesizer Interface/Memory (MFP-A4): Card 794275 (Backup Battery missing);
I/O Interface (232M-A3): Card 796037-2;
1-Hz Option (A2): Card 796022-2;
1st-3rd LO Synth (A5A1): Card Ass'y 791630-4;
2nd LO Synth (A5A2): Card 791601-2;
10-Hz BFO Synth (A5A3): 796181-2.

I noticed that the two LED's in the 1-Hz Option Card (796022-2) near the shield aluminium can glow for a while at startup and turn off quickly (one of them remains lit for a few seconds instead); also the DS-1 LED in the 10-Hz BFO Option Card (796181-2) glows (and turns off suddendly).
I noticed also that the TO-3 transistor (Voltage regulator?) that is located behind the front panel (near the meter, almost at the bottom) becomes hot quickly (the temperature of all the other voltage regulators seems to be normal instead).
Can anyone help me? Thank you very much in advance!

Incidentally: has anyone the Schematic Diagrams (and/or the description, Parts List and location of components) of the 1-Hz Option Card (796022) and of the 10-Hz BFO Optional Card (796181)? They could be very helpful for me!

Thanks again, best regards and 73,

Paolo

- Paolo Viappiani
Via G. B. Valle 7
19124 La Spezia, Italy
Phone: ++39-187-21647
email: pviappiani at tin.it  
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