Silver ST-757 tuning meter issue

H3NK3L

Member (SA)
Dec 17, 2020
159
121
43
France
Hello,

Short version : VU-meter indicating tuning level not working on FM
FM reception/stereo/... working fine. Tuning meter going to 5/5 when FM switch is selectedthen 0/5 and remains there no matter what signal strength. Tuning indicator seems to work fine on the other 3 bands.


Longer version

Recently got a Silver St-757 (in pretty bad shape) - The VU-meter on this thing seems to work fine on SW/LW/MW but does nothing on FM,
MPX and Stereo are set correctly (great stereo seperation, stereo led goes on when it has to).

Odd thing : the pcb had been bent and was slightly off - due to someone disassembling and reassembling a bit amateuristicly to say the least, it even had some wood-screws in it, lacked a few screws here and there, ... had one of the 3 belts replaced with in incorrect one....

Got everything up and running again, and things are sorted out for FM reception, tape deck plays like a charm, recording works like a charm, VU-meters (leds) work great,....
Just cant seem to get the Tuning VU-meter to work - when set to FM the needle goes all the way out (to 5 out of 5) and goes back and remains quietlyu sitting at 0 , no matter how good or bad the reception.

I only could find a "service manual" - more or less nothing more than a electronics schematic (no pcb, no indications just the logics schematics) - the odd thing is tuning analogue vu works with 3 bands just not on FM - it sometimes worked as long as the pcb was bent... so I already checked all contacts and circuits for broken or interrupted paths, refluxed and resoldered most of it, that brought back Stereo (I only had mono, no matter what mpx / stereo setting on the VR's).

So all is working fine...except for the VU-tuning indicator meter......on FM

Anyone had this kind of issue or possible solution or idea of where the problem may be ?

Thanks for any lights anyone may shed on this mis(t)ery
 

H3NK3L

Member (SA)
Dec 17, 2020
159
121
43
France
Issue solved, got my hands on a service manual... Rechecked every single component on the fm-tuning level path... Found a microcrack in ONE resistor... Replaced it... And look and behold... Fm tuning meter works fine again :)

(any moderator doing some cleaning, feel free to remove this post)