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Repeatedly blowing channels on MCA-50 amp?

GoMrPickles

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I have a Marantz AV8802A connected to an Anthem MCA-50 for home theater use (front/center/right only). I had the MCA-50 repaired by Anthem/Paradigm in 2018; the capacitors were replaced on all five channels. (I'd like to downsize this whole system, but that's a question for another thread.)

A little while after getting the 8802A (also 2018), the center channel on the MCA-50 blew. I moved the "center" to an unused channel on the MCA-50. It was fine for a few years but blew a few months ago. I moved the center to the last unused channel on the MCA-50, and it blew last night. ("Blew" -> sound cuts out or gets garbled.)

The left and right channels have been fine for years; it's just the "center" that goes. We listen at low volumes, usually -50 to -40 dB on the AV8802A. Could this be an issue with the AV8802A, or did I just get a bad repair on the MCA-50? Amp channels should not die after a couple of years of light use, let alone a few months or weeks.

I'm going to find a local shop to work on it; hopefully it can be repaired for not-too-much and I'll sell it after.

TIA.
 
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GoMrPickles

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What center speaker you use?
It's a Polk Audio something-or-other I got for $200 used. (Lots of space constraints... I'm looking to get rid of this thing, too.)

Connection from the AV8802A to the MCA-50 is XLR balanced cables, probably Monoprice cables or something similar.
 

tomtoo

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It's a Polk Audio something-or-other I got for $200 used. (Lots of space constraints... I'm looking to get rid of this thing, too.)

Connection from the AV8802A to the MCA-50 is XLR balanced cables, probably Monoprice cables or something similar.

If I blow always with that speaker my amp, i would be sceptical about that speaker.
 
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GoMrPickles

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If I blow always with that speaker my amp, i would be sceptical about that speaker.
It happened with a Paradigm Studio CC v2, back when I first got the MCA-50... but not with the Studio 100 v2's that the L/R channels were driving. So I guess the only common thread amongst all of these is the center channel output on the AV8802A, but I've never heard of a processor blowing an amp. It doesn't seem like the output levels are such that that would happen. Unless something is busted in the AV8802A, I guess?
 

DonH56

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I have a vague memory of some Marantz preamp outputs injecting a signal burst or DC offset, maybe just at start-up. No idea if it applies to your AV8802A, maybe do a search or check the threads on AVS? And I could be misremembering...
 
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GoMrPickles

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I have a vague memory of some Marantz preamp outputs injecting a signal burst or DC offset, maybe just at start-up. No idea if it applies to your AV8802A, maybe do a search or check the threads on AVS? And I could be misremembering...
I posted in the AV8802A thread on AVS forum; I also took the AV8802A in to a local repair shop. They said it was a bad HDMI board, which was also suggested by a few folks on AVS Forum. I'll get it replaced ($700, bleh) and then figure out if I should keep using or resell the thing. The HDMI board was suggested as a culprit by a few ppl on AVS; apparently the unit runs hot enough (it does get very hot) to cook itself. Great. I was using it in an open cabinet with ~4" clearance above it, but that may not have been enough... or it may have been bad since I bought it.

I tested the amps one channel (laptop/dac/amp/one speaker channel) at a time and didn't hear any issues.
 

DonH56

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I posted in the AV8802A thread on AVS forum; I also took the AV8802A in to a local repair shop. They said it was a bad HDMI board, which was also suggested by a few folks on AVS Forum. I'll get it replaced ($700, bleh) and then figure out if I should keep using or resell the thing. The HDMI board was suggested as a culprit by a few ppl on AVS; apparently the unit runs hot enough (it does get very hot) to cook itself. Great. I was using it in an open cabinet with ~4" clearance above it, but that may not have been enough... or it may have been bad since I bought it.

I tested the amps one channel (laptop/dac/amp/one speaker channel) at a time and didn't hear any issues.
Well, that is annoying! I can see the center amp channel going bad if it is in the middle of the chassis where it can really heat up, but strange that the HDMI board would fail only for the center channel. Guess that is where the signals are demodulated to discrete channels?

Maybe try one of those coolers that sits on top to suck out the hot air? (I could use a hat that does that but I am a renewable source of hot air...)
 
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GoMrPickles

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Well, that is annoying! I can see the center amp channel going bad if it is in the middle of the chassis where it can really heat up, but strange that the HDMI board would fail only for the center channel. Guess that is where the signals are demodulated to discrete channels?

Maybe try one of those coolers that sits on top to suck out the hot air? (I could use a hat that does that but I am a renewable source of hot air...)
I found this post about replacing the board; frankly $700 seems like a bargain. If I decide to use the processor again, I might try one of these. That said, the wife was pretty excited when I moved all the gear from the living room to the garage...
 

peng

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It happened with a Paradigm Studio CC v2, back when I first got the MCA-50... but not with the Studio 100 v2's that the L/R channels were driving. So I guess the only common thread amongst all of these is the center channel output on the AV8802A, but I've never heard of a processor blowing an amp. It doesn't seem like the output levels are such that that would happen. Unless something is busted in the AV8802A, I guess?

Have you measured the AV8802A's center channel pre out dc and ac voltage? That's easy to do if you have a multimeter. I highly doubt it is the issue but it should be measured just in case.
 
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GoMrPickles

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Have you measured the AV8802A's center channel pre out dc and ac voltage? That's easy to do if you have a multimeter. I highly doubt it is the issue but it should be measured just in case.
I have not; it's at the shop for a while for repairs. I can check that when I get it back.
 
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