EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: manfredkallfass on January 14, 2017, 03:15:44 pm
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Dear all,
I bought a marantz 75 SR 1040 amp 2 years ago.
After 1 year it started "muting" itself for some seconds, mostly when the volume was a little bit high (not THAT high tho). It muted with a sort of "click" - the same sound of when it turns on or off.
It looked like it actually went off during the peaks of amplitude...like a volume protection.
Then at one point it just went bananas and it won't play anymore. It did not even turn on.
I changed one of the fuse, which was burnt, and when i turned it on again it burnt the new fuse.
I have had no time to work on it for one year. Now i have a little time and I would know if your knowledge can let me understand where to start from to repair it...(maybe capacitors are gone...?). If needed i can send you some more details, pictures, ...
The speakers I was using were quit bad, found in the trash: 8 ohm, they handle 10 to 90 W each. 98db/1w/1m as sensitivity if that matters... One of them has a destroyed woofer. :D
Thank you, all the best,
manf
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It was an exceptionally bad idea to use known defective speakers. You now have at a minimum one amplifier channel blown (possibly both channels).
The output transistors for at least the one channel are now shorted; quite possibly other parts such as driver transistors, resistors, diodes, bias transistor, etc damaged as well.
Easy job for an experienced technician, probably challenging for a novice.
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Thanks for the answer, not very encouraging but I will try to look at it if i get some time. Or get a new amp. And a new speaker.