Realistic STA-2000 AM works but no FM at all

[bradyhylla]

Hello there folks,

Picked it up from Savers several months ago (with a Lab 400 ). Got it home and no sound at all. After alot of chasing down problems, all new electrolytics, contact cleaner, snake pit of wires and lots of desoldering - labeling - and soldering I managed to get er all working. EXCEPT, I get absolutely NO FM at all. It doesnt even sound like its trying to pull in any stations and the meter has absolutely no deflection at all.

I am ok with reading schematics and can usually manage to get things working again but troubleshooting FM circuits is a mystery to me and there doesnt seem to be much on youtube to guide me through troubleshooting FM circuits.

Has anyone else had this problem with this receiver or a similar receiver? Any suggestions on where i should start troubleshooting? Any help would be greatly appreciated.

 

[gadget73]

first thing first, make sure the FM tuner circuits have proper voltage going to them. I don't have a schematic handy (got a link to the one you are using?) but some things turn voltage off to the tuner(s) when not in use and crunchy contacts in the switch could do it. Also not sure the specific config on this but a lot of gear has the metal "can" around the tuning condenser where the RF amp, oscillator, and mixer live, a board where the IF and detector live, and sometimes the stereo decoder will be on that board or a separate one. Need to verify voltage on all of it.

Beyond that, what do you have for test equipment? Absolute bare minimum will be a good voltmeter but to really do tuner work you need a signal generator and a scope, and for alignments it needs to be a sweep generator and an FM stereo generator to do the whole thing properly.

 

[Binkman]

Welcome to A.k.
if you don't have the service notes go to bottom page "Service Info"
ttps://www.hifiengine.com/manual_library/realistic/sta-2000.shtml

 

[Ylli]

Gadget73 has got you on the right track I think. But I'll add some specifics. Find the AM/FM IF & MPX board. Hopefully the wires that connect to it are numbered. Using your voltmeter, you should find about +13 volts on terminal 9. You should see just a little bit less on terminal 8 (call it +12.5 for reference). Being sure the receiver is set to FM Stereo, you should also see +12.5 on terminal 3. The above is power into the AM/FM IF & MPX board.

The +12.5 at terminal 7 also goes to switch section SA-5, and when SA-5 is in the FM position, power is supplied to the FM Front end on terminal 5. I would expect to see +12.5 volts there. If you have difficulty locating terminal 5 on the FM front end, look for the junction of a 10K and a 4.7K resistor. Look for that +12.5 volts on the end of the 10K *not* connected to the 4.7k .

Found this: