spaghetti
Active Member
Hi, I have 2 of these vintage receivers, they both show the same issue with FM stereo, there are very few stations that are received in stereo. I am trying to figure out if I can do something to improve the situation.
I recapped the IF and MPX sections of one receiver, but things are unchanged. Most of the cap values were off by 50%. Of course the stronger the signal, the more likely FM stereo will engage. But I noticed a strange behavior: I expected stereo to kick in when the signal is at the highest, but many times it kicks in earlier and goes out just before the signal reaches its peak.
There's not much to adjust on the MPX board, I uploaded the tuner section schematics here: https://i.imgur.com/rcdrCYBr.jpg and the adjusting points here: https://imgur.com/KfYUhei
so my guess the issue is in the FE or the discriminator.
Any suggestion of what could be the issue? What parts should be aligned? I have an oscilloscope and a signal generator that covers also FM frequencies with a 1Khz internal oscillator.
Thanks!
I recapped the IF and MPX sections of one receiver, but things are unchanged. Most of the cap values were off by 50%. Of course the stronger the signal, the more likely FM stereo will engage. But I noticed a strange behavior: I expected stereo to kick in when the signal is at the highest, but many times it kicks in earlier and goes out just before the signal reaches its peak.
There's not much to adjust on the MPX board, I uploaded the tuner section schematics here: https://i.imgur.com/rcdrCYBr.jpg and the adjusting points here: https://imgur.com/KfYUhei
so my guess the issue is in the FE or the discriminator.
Any suggestion of what could be the issue? What parts should be aligned? I have an oscilloscope and a signal generator that covers also FM frequencies with a 1Khz internal oscillator.
Thanks!