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marantz 4240 pop

jFF_Bulbo

Active Member
hello everyone.
I have a Marnatz 4240 under repair, the left amplifier failed and I was able to repair it, however a problem appeared that I had not noticed before working on it.
When the selector (S001) is placed on the FM input, when the speakers are activated, it emits a very loud noise, even the DBT lights up completely, and the FM is not heard.
In all the audio inputs, CD-4, phono, tape, a noise is heard, low in volume but always present, which does not depend on the volume at which the equipment is placed.
I have completely disassembled the front, checking cable by cable and I have not found anything suspicious.
I have disconnected J701 in both amplification circuits to connect my phone directly to these stages, and they work without the noise that I mentioned.
on power suply i changed C804, C805, R812, R811, H809 (diode) and the problem still hapening.


Has anyone gone through this problem?

thank you very much for your help
 
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Were you able to solve this problem? I have the same issue. Thinking the power supply is not sending the correct voltage to the FM circuit, but am just beginning to troubleshoot and cae across this post.
Thanks
 
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