Let me start by saying that I was a CET in the 70s but have not worked on a tuner since then. I have a scope, millivolt meter, DVM and function generator, but not a sweep generator. I have had this Sanyo Plus 55 receiver for 5 years, I made discreet replacements for the STK Darlington packs, and mainly keep it for the tuner. The tuner has gotten to the point that it will not pick up anything on FM unless the stereo muting is on and even then the reception is poor. It used to be quite good. I hooked up another receiver to the antenna and it worked great.
I checked the voltages on IC201 (LA1231N) FM muting chip, all except 13 and 16 are correct. 13 is 0.131vdc and 16 is 0.154vdc. I pulled C210/C212/C330 and they are fine. The voltages on IC301 are correct. I wonder if this chip is bad or is there a likely culprit I should be looking at?
Thanks
I checked the voltages on IC201 (LA1231N) FM muting chip, all except 13 and 16 are correct. 13 is 0.131vdc and 16 is 0.154vdc. I pulled C210/C212/C330 and they are fine. The voltages on IC301 are correct. I wonder if this chip is bad or is there a likely culprit I should be looking at?
Thanks
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You can proceed by replacing the LA1231N IC. However, that does not guarantee the board's functionality. If changing the IC does not solve the problem, some other component connected to the IC maybe bad. Please check if some other component is getting extremely hot or looks physically damaged. Also check with a multimeter if there is a broken trace or short circuit.