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Marantz 4140 - Issue with phono channel

S

Sebio

New Member
I've recently picked up a 4140 as my first proper amp but its having some interesting issues.

Starting the amp up using the Aux channel with a cell phone connected works great. As soon as I switch to phono channel with my turn-table hooked up, audio is very quiet and I get some subtle popping/static noise.

Going back to the Aux channel from the Phono channel, the audio is quiet like in the phono channel. I can also subtly here the phono channel leaking through. When I unplug my phone and plug it back in, the volume goes back to normal.

So far, I've thoroughly cleaned all the pots, and replaced the 1uf caps on the preamp and phono board.

I'm pretty savvy with working on electronics, but this is my first amp repair.
Any ideas what could be causing this or where I should be checking? Any tips or info would be greatly appreciated!
 
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Is there good DC power on J306? Maybe you have a broken wire, see if you can follow it from J306 to ???

Tom
 
catrafter said:
Is there good DC power on J306? Maybe you have a broken wire, see if you can follow it from J306 to ???

Tom
Click to expand...
J306 is pulling around 0.2V. I'm not sure what it should be pulling but in the process of checking things, It seems to be working correctly now, and I cant seem to recreate the issue. I'll keep an eye on it for now I guess.

I appreciate you coming in to help. I definitely want to learn more about servicing these type of amps.
 
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