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Mcintosh MC240 Hum on one channel, need help

lens42

Member
2008-03-16 8:05 pm
I’ve noticed in several MC240s that the 12k 2W plate resistors don’t age well and can be way off. The signal path is push-pull throughout, which normally rejects supply ripple, but If a component in one side of one channel is way out, it could cause an imbalance in that channel, reducing ripple rejection. You may *also* have a weak supply filter cap, with the good channel still valiantly rejecting ripple.
 
I’ve noticed in several MC240s that the 12k 2W plate resistors don’t age well and can be way off. The signal path is push-pull throughout, which normally rejects supply ripple, but If a component in one side of one channel is way out, it could cause an imbalance in that channel, reducing ripple rejection. You may *also* have a weak supply filter cap, with the good channel still valiantly rejecting ripple.


That's quite a good diagnosis, and certainly shows you have some education/experience in the matter.
Made my day.
:)