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Sony TA-N80ES Power Amplifier

Hi. First time user here. I hope this post is in the appropriate place.

I found this site when I was looking for documentation for my Sony TA-N80ES power amplifier, which after 25 years or so of being on literally 24/7, I discovered the other day was no longer outputting to the connected speakers (which I have confirmed are working.) There is no external fuse cap. I was hoping to find that that there is an easily-accessible internal fuse that might be blown. I found the pdf service manual here at hifiengine (https://www.hifiengine.com/manual_library/sony/ta-n80es.shtml), but I am not a technician and though I'm comfortable doing maintenance inside a desktop computer, I must admit I can make almost nothing of the Sony's schematic. The pdf file is just scanned images, and is not searchable.

I'm posting here in search of some guidance. Here's more detail on the situation.

The amp still gets hot when powered on. But the speakers (Yamaha NS-10M's, other test units) receive no signal.

The amp was plugged into a typical 6-outlet power strip, which was in turn plugged into some kind of (no doubt cheap) surge protector before plugging into the wall. Also on that same power strip was the studio computer, video monitor, and some other lighter stuff.

NOTE 1: There was an unrelated power failure of the entire house between the last time the amp was known to work, and when I found it was no longer driving the Yamahas. Before the power was finally turned back on for good, the power went on and off a couple of times. My first thought was somehow the outage was responsible for the amp's problem, especially given that that the outage and the two false returns of power were among the very few times in 25 years that the Sony had ever been without power and not switched on. (The thing is a monster!)

NOTE 2: Following the outage, NONE of the other items that shared the power strip with the Sony amp showed any signs of having experienced a power surge or other problems. The computer needed rebooting, but that was it. Nor was the power strip's breaker tripped during the outage.

I'm not sure what this adds up to, but I suspect there might be clues as to what can be ruled in and out from those two Notes.

Offhand, I'd guess that the facts of Note 2 argue that the power outage in the house had nothing to do with the TA-N80ES's failure. But I don't know.

The fact that the amp is still drawing power, but not outputting to the speakers, I'd guess means that the problem lies deeper than a fuse or circuit breaker to protect from AC surges. But again, I don't know. I have not opened the casing, but sniffing around the top and bottom grilling, there is no odor of a burned out component.

I'm hoping that it's a fuse of some kind, and changing it would be along the same lines as changing a CMOS battery on a motherboard, but something tells me that won't be the case.

Any ideas? Is there a fuse that I might be able to change? How much disassembly would be involved?

Thank you!

Re: Sony TA-N80ES Power Amplifier

That amplifier is quite complex. I don't see any fuses that are easily replaced; there are quite a few fuse resistors that can go bad, and stop the amplifier from functioning. Most are in the power amp section and some are in the protection circuit. This looks like a job for a technician.

Re: Sony TA-N80ES Power Amplifier

Thank you, Johnnysan. That's just the kind of reply I was looking for -- though I'd been hoping for a happier diagnosis, like learning there would be an easily-accessible fuse as soon as I popped the case open!

When I asked elsewhere, someone told me that the amp "uses relays to switch the speakers and if the relay is defective as often happens" there would be no sound.

Does that sound right, or plausible?

Thanks again.