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McIntosh MX113 what is the voltage source for the FM tuner?

E

Ethan Pierce

New Member
I am trying to remedy the FM tuner, there is no signal, no hum or noise at all. All other functions on the preamp work fine, AM is fine and everything.

I am getting a reading of 3v all the back to the IF chassis but I am unsure what components actually supply the correct 24v to the FM tuner. Anyone have experience with this issue?
 
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PE9ZZ said:
S301 rear wafer. The service manual is pretty clear.
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I guess I am more unfamiliar with how the FM works on this tuner than I thought. It was my understanding that the tuner pulls from the power supply 044-576 to the IF chassis then to the MPX and then through the preamp. Upon further inspection I am only getting 3v from the power supply as well, all the way back through Q201 (which has seemed to have left dark burn marks on the PCB)
 
It is a so-called preceiver, a receiver without output amp. Its construction is unusual because of the 24 V rail. But it looks like you found the cause. It is annoying McIntosh obscures the part numbers. Fortunately the power supply can be fixed with many alternatives because they are not critical.
 
PE9ZZ said:
It is a so-called preceiver, a receiver without output amp. Its construction is unusual because of the 24 V rail. But it looks like you found the cause. It is annoying McIntosh obscures the part numbers. Fortunately the power supply can be fixed with many alternatives because they are not critical.
Click to expand...
That is good to know, I will attempt to find the best replacement. I had taken the output transistor out and measured it with my mm. The readings still seemed like it was putting out a good amount of current but to be honest I don't know what exact numbers I am looking for. I am used to fixing speakers, turntables, and recapping receivers. FM troubleshooting is new to me, I don't know anyone personally that knows anything about it and I am not sure how deep I actually want to get into it because it seems like a it's time and tools investment I might not be ready for. Someday for sure but this is unit is working perfectly otherwise so fixing this would make it cherry. I will let you know how the transistor swap goes and we can go from there. Thank you for you help!
 
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