The Fisher 500T No FM Stereo

[Sterling245]

Hi everyone! I've been working on a Fisher 500t and cannot seem to get FM stereo. The unit has been recapped as well as other bad/out of spec parts replaced. The stereo lamp does light indicating that it is receiving the 19khz pilot, but upon checking with my Sencore SG-165, I confirmed that it is still mono. I have not messed with the tuner allignment as it appears to be quite good as it is. In addition to the no-stereo problem, I do not believe FM muting is working either. I can live without muting as I would never use it anyways, but I would like to get FM stereo working properly. Prior to posting this I did the 6-way test on all the transistors on the MPX board (they are socketed, so easily accessible), and all appear to be good. Has anyone else had this problem and/or have an idea as to what might be causing it?

 

[Punker X]

Hifiengine has to different manuals an early and late. MPX looks pretty much the same layout. Having a SG-165 you should be able to attempt the alignment on it. Make you have the correct alignment tools, you don't want to crack any of the tuning cores.

 

[Sterling245]

If I remember correctly it is the later one. I have a copy of the correct service manual. I was reluctant to try and align it before addressing issue with the MPX as I don't want to risk making the problem harder to fix...

 

[Punker X]

If I remember correctly it is the later one. I have a copy of the correct service manual. I was reluctant to try and align it before addressing issue with the MPX as I don't want to risk making the problem harder to fix...

The problem may be that it is not adjusted correctly. Just because you get a stereo lamp doesn't mean the 19Khz is good. There's a trigger adjustment there. You can probable adjust that so the stereo lamp is on most of time.