Long time reader, but first time member to AK. I need some help with my CR-620. Like other folks, I obtained this Yamaha for the spare change in my pocket at a garage sale. Bought it mostly because of the way it looked. It has been my trusty garage unit for some time, and I recently decided to give it a tune up as it always sounded a bit flat. The only item not functioning was the FM-Mute mode. Well, after replacing the electrolytics, discrete transistors, and a few diodes, the unit sounds wonderful. However, the FM Muting mode still does not work.
When FM Muting is selected the sound goes off. I can still hear the stations if I crank the volume to 10. The FM Muting circuit on the CR-620 is pretty basic and just puts a higher voltage on pin 6 of IC201. I have confirmed all the voltages in the path, and confirmed the FM Stereo LED is good. The only thing I have noticed is that the voltages on the IC201 LA3350 IC are ~500mV low vs the schematic, including the power pin (11.9V vs 12.4V per schematic). My next step would be to replace the LA3350, but I have read on other threads that these are pretty tough ICs.
I have been raking my brain on this one for a couple weeks and it seems I am missing something simple. Help!
Note: I do not have access to scope or signal generator.
When FM Muting is selected the sound goes off. I can still hear the stations if I crank the volume to 10. The FM Muting circuit on the CR-620 is pretty basic and just puts a higher voltage on pin 6 of IC201. I have confirmed all the voltages in the path, and confirmed the FM Stereo LED is good. The only thing I have noticed is that the voltages on the IC201 LA3350 IC are ~500mV low vs the schematic, including the power pin (11.9V vs 12.4V per schematic). My next step would be to replace the LA3350, but I have read on other threads that these are pretty tough ICs.
I have been raking my brain on this one for a couple weeks and it seems I am missing something simple. Help!
Note: I do not have access to scope or signal generator.
