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Help with MA5100

Fridge · 2020-02-07T21:44:29+00:00

I was given a MA5100 amp by a friend to clean up and refurbish. I am a newby at trouble shooting and can use some help. I recapped all electrolytics and some other caps in the audio path. The unit is only putting out about 4 wpc. I tested voltages throughout including all transistors. All voltages are fairly close to the schematic many are a bit high but pretty much not more than 10% high. The only issue I can find is that resistors R231 and R232 are severely overheating....discolored - burned the pcb - backside is browned. Both L and R channels are performing identically. I am trying to avoid the mistakes I have made in the past by shot gunning parts and in that process ruining the stereo...I have ruined a few, but have had more successes. What volume I do have is nice, full and clean...If any one can offer some suggestions to set me on the right path to solve this problem I would greatly appreciate it. Thanks!

Thread starter Fridge
Start date Feb 7, 2020
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ma5100 mcinstosh

Fridge

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Mar 7, 2020

Update, I pulled the triacs-one tested bad. I also found an open resistor in the power supply section. replaced bad parts and unit came back to life with a clean 45 wpc and sounds terrific! Now back to refurbishing a Thorens TD 124 that I got with the MAC.

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