Older Sony AV surround amp suddenly gone all Protect Mode on me

I  have a Sony STR-K750P 5-channel 5.1 surround amp with small self-powered remote sub.  The whole setup was an everything-in-one-box kit.  It isn't much but it serves the living room TV and videogame setup well enough.  It's a minimum of 15 years old and wasn't really expensive to begin with.  It don't owe me nuthin.

Nonetheless it has done its job flawlessly and without complaint, every night until tonight.  DW turned on the setup as usual, there was a quiet 'pop' and the receiver went into PROTECT mode.  There have been no changes to inputs, outputs, or source media in about 5 years.

Tried unplugging it for a few minutes and restarting, to the same result.  Disconnected it from all input / output connections, same result.  It's currently sitting on the bench with the cover off, unplugged, and I blew all the dust out of the chassis with a compressed air can electronics cleaner.  In a few minutes I'll try again, but I expect the same results. 

Anything I'm missing?  I don't see any obvious thermal switch to reset, and anyway it wasn't hot because this was first fire up of the day.  Is it just time for a new one?

Thanks!

[edit] 

Tried letting it sit unplugged for 20 minutes to let the caps discharge.  Failed a few seconds after startup (basically as soon as the main amps come online, same as before).  Also tried reinitializing it by holding in the power button for 5+ seconds. Reinitialized and then failed into Protect mode.

Going to try leaving it unplugged overnight, just in case there is residual energy in the caps, but that's a hail mary at best.

Assuming the worst, what's the state-of-the-art in moderately priced 5 + sub surround amps these days?  General purpose movies, TV, and gaming.  We don't need it to shake the paint off the walls.  In fact, some dynamic range compression would be nice.  My hearing ain't getting any better.

Left it overnight, plugged it in, turned it on, click - straight to protect fault.  It's toast.

Duke said:

Assuming the worst, what's the state-of-the-art in moderately priced 5 + sub surround amps these days?  General purpose movies, TV, and gaming.  We don't need it to shake the paint off the walls.  In fact, some dynamic range compression would be nice.  My hearing ain't getting any better.

 

This all depends on your budget and if you want to remain with a 5.1 system. 

"They say" there are many good soundbar options these days, but I don't buy it. I prefer old school integrated AV amp/receiver, and speakers you can really crank some music through.

Amps usually go into protect mode when impedance is too low on one or more outputs. Usually caused by a pinched cable causing a short. If you've unplugged all the speaker cables !at the amp! and it still goes into protect it's probably an internal short or something  fried and usually isn't economical to repair. As far as replacement recommendations I have none. My only other input is that most sound bars are decent but there is no replacement for a good external sub. 

barefootskater said:

Amps usually go into protect mode when impedance is too low on one or more outputs. Usually caused by a pinched cable causing a short. If you've unplugged all the speaker cables !at the amp! and it still goes into protect it's probably an internal short or something  fried and usually isn't economical to repair. As far as replacement recommendations I have none. My only other input is that most sound bars are decent but there is no replacement for a good external sub. 

There are many 2.1 soundbar systems that have a separate powered sub. 

In reply to z31maniac :

I definitely want to stay 5.1 for this room.  I have 5 reasonable speakers in place plus the sub.  There is no reason any one of those should be the issue, since none have moved or been changed since installation 10+ years ago.  The wiring is mostly concealed and protected.  I suspect an internal fault in the receiver itself.

Budget is not a serious issue but I am no longer the audiophile I once was so anything that has decent amp capacity and reasonable sound quality will be fine.  I don't see much reason to spend more than a few hundred bucks.

Thanks!

Duke said:

In reply to z31maniac :

I definitely want to stay 5.1 for this room.  I have 5 reasonable speakers in place plus the sub.  There is no reason any one of those should be the issue, since none have moved or been changed since installation 10+ years ago.  The wiring is mostly concealed and protected.  I suspect an internal fault in the receiver itself.

Budget is not a serious issue but I am no longer the audiophile I once was so anything that has decent amp capacity and reasonable sound quality will be fine.  I don't see much reason to spend more than a few hundred bucks.

Thanks!

 

Still probably worth it to disconnect all of the speakers and see if the problem fixes itself. It is possible that a rat/mouse chewed through a speaker wire, or else something on one of the speakers failed - HIGHLY unlikely, but you'd want to eliminate the possibility, if only to protect the new receiver. 

In your price range, I'm partial to Yamaha, but I think you'll probably be fine with any 5.1/5.2/7.1/7.2 from Onkyo, Denon, or Yamaha in that price range. Sony too, but for some reason I've never been a fan, despite owning a receiver of theirs for a long time. 

When I was in electronics school in the Air Force an instructor once said that electronics fail once you let the magic smoke out. 

Try unplugging all the speakers and see what happens. Edit see that was already suggested. 

Yeah, to be clear, I disconnected all the inputs and outputs last night and tried resetting it several times while only plugged into the wall.  Left it overnight completely unplugged from everything and only plugged the power cord in this morning.  Tried the power and it went to immediate fault condition as soon as the amps kicked on.

Dead horse is dead.  I'll stop beating it.

I've had good luck with Yamaha, too, mtn, and I like Denon.  I always bought Sony TVs from back in the CRT days with good luck, and this little 5.1 setup came as a heavily-discounted add-on when we bought our last big Trinitron CRT at least 15 years ago (and probably closer to 20?).  I can't complain about that.

Is optical input still a thing?  My TV is 10 years old and running fine.  If I recall correctly I'm running optical out of the TV to the receiver for digital sound.  With a newer receiver I may have more options but I honestly don't recall what the TV will output in the way of digital audio.

Thanks for everybody's input.

In reply to Duke :

Optical is still a thing. Or it was 3 years ago when I bought my garbage soundbar. 

Paying close attention to this thread for when I finally get to upgrade

Optical has mostly been replaced by HDMI, but it looks like most receivers still have at least one optical input. See one linked below - that isn't a recommendation for that receiver, although it is probably pretty damn good, it is just the first one that I saw on my search. 

https://www.crutchfield.com/p_022RXV385/Yamaha-RX-V385.html

I had a Sony STR-DE597 do exactly the same thing.  Started out going into protect mode occasionally, got progressively worse and finally just would power up and immediately go into protect mode.  Since it started slowly and got progressively worse, and the protect circuit is triggered by overcurrent on the output stage, it's probably an electrolytic cap that was going bad.  I just gave up on it and bought a Pioneer VSX-532 which is just fine for my needs.  I have another AV receiver in my home theatre room, a Pioneer VSX-1022 that has been cranking along just fine for about 12 years, so I'm pretty pleased with them.

mtn said:

Optical has mostly been replaced by HDMI, but it looks like most receivers still have at least one optical input. See one linked below - that isn't a recommendation for that receiver, although it is probably pretty damn good, it is just the first one that I saw on my search.

https://www.crutchfield.com/p_022RXV385/Yamaha-RX-V385.html

Thanks.  I have no particular interest in sticking with optical but if my memory serves that is my only option for getting digital audio out of my TV.  It may, however, have been my only option for getting digital audio into the receiver.

stukndapast said:

I had a Sony STR-DE597 do exactly the same thing.  Started out going into protect mode occasionally, got progressively worse and finally just would power up and immediately go into protect mode.  Since it started slowly and got progressively worse, and the protect circuit is triggered by overcurrent on the output stage, it's probably an electrolytic cap that was going bad.  I just gave up on it and bought a Pioneer VSX-532 which is just fine for my needs.  I have another AV receiver in my home theatre room, a Pioneer VSX-1022 that has been cranking along just fine for about 12 years, so I'm pretty pleased with them.

This one went from literally working every time for 15+ years to not working at all in one shot.  I'll look into Pioneer stuff too.  Thanks!

Yeah, something went Poof due to age.  Don't know if you're inclined to dig into it, but this guy does:

In reply to 1988RedT2 :

Yeah, I saw that, and my inner cheapskate briefly toyed with the idea.  But I'm not busting out my soldering skzillz on a receiver pushing 20 years old that was a mid-level consumer model even then.

With the speaker comment, I'd just buy the nicest Onkyo (I'm partial to Onkyo over Denon) you feel like spending the money on, hook everything back up and enjoy.

Duke said:

In reply to 1988RedT2 :

Yeah, I saw that, and my inner cheapskate briefly toyed with the idea.  But I'm not busting out my soldering skzillz on a receiver pushing 20 years old that was a mid-level consumer model even then.

 

I think you've made the right decision!

Very few of my forays into consumer electronics have ended well.  I consider myself older and wiser.

OK, front runner right now is the Yamaha RX-V485 at $399.  We've recently made the plunge to Google Home and this offers connectivity and decent performance. 

The other option is the Denon AVR-650H also at $399.  The Denon also offers Google Home connectivity.

Right now I switch cable and gaming sources at the TV and output all the audio from the TV to the digital audio in on the receiver.  The sales person at Crutchfield was suggesting that I do the reverse and switch sources at the receiver and pipe video only out to the TV.

The only problem I see with this is that neither of these receivers are Chromecast compatible, which is not an issue if I go from TV > Receiver as I have been.

If it really is better that I go Receiver > TV, then the Yamaha is the stronger winner because it has 4k upscaling, which the Denon doesn't.

Thoughts?

Onkyo doesn't seem to offer Google Assistant interactivity.  They are Cnet's current favorite, but they like the 7.1 unit and I don't really think I need 7 channels in this room.  Plus it's huge and I'm not sure it will fit where I need it to.

Duke said:

Onkyo doesn't seem to offer Google Assistant interactivity.  They are Cnet's current favorite, but they like the 7.1 unit and I don't really think I need 7 channels in this room.  Plus it's huge and I'm not sure it will fit where I need it to.

 

A cool feature with many of the 7.1 receivers, if you ever decided did want a bit more oomph from the system, you can change the settings and bi-amp a big set of front mains.

OK, Battle Royale time:  Sony STR-DN1080 versus Yamaha RX-V585 versus Denon AVR-S750H

PICK YOUR WINNER - Budget is $500 and won't go up any further. 

We've decided to throw an extra c-note into the pot and step up a model.  We probably won't use it now but we're looking at 7.2 systems; many offer 2-zone flexibility with 5.1 in one room and 2-channel in another, or bi-amping as described above.  They also seem to offer some more future-resistant encoding options and additional HDMI inputs.  Some of the units in this price range offer a little more wattage; some don't.

I know the Onkyo TX-NR696 has gotten good reviews, but it just won't fit in the space we have to put it.  We're limited to a little over 13" deep and the Onkyo is pushing 15".

I am open to entirely other suggestions, too.

Thanks!

[edit] I have a mild preference for one of those three above, but I will keep it to myself for right now.  I also have a least favorite, but again, only by the slimmest of margins.

I'm personally soured on Denon, I've killed two of their mid-level receivers over the past decade playing them LOUD. 

And for some reason, I have an inherent bias against Sony. No real or explainable reason, but they feel like BOSE to me. There is no value there, just the name.

I was going to suggest the Onkyo TX-NR777 I currently have until I realized it doesn't meet your size requirements and it's approaching $600 at Best Buy. 

OK, thanks.  I've been partial to Sony TVs all my life, and this previous AVR just came as a package at a deep discount with the TV.  I've got no complaints and it's done its job but I'm not sold.  It just seemed like when I bumped the budget a little Sony popped back into the mix.

The Denon is my mild favorite because it includes eArc compatibility.  That's not a factor right now but seems like it will help in a couple years when I go to a 4K TV.

Denon reviews have mentioned it was a little quieter than others.  I hear your comments above but I don't know how hard I'm going to exercise it - the speaker setup is not that big and there is the powered sub to help with the heavy lifting.  Nonetheless if I go that route I will keep your caution in mind.

Thanks again for all your input - I appreciate it.  I've been out of this arena for quite a while and it's been a significant couple of decades.

z31maniac said:

And for some reason, I have an inherent bias against Sony. No real or explainable reason, but they feel like BOSE to me. There is no value there, just the name.

I feel the same way. I actually had some bad experiences with Sony making me think they were taking advantage of their past reliability reputation. I have since had some positives, though. I would consider them low-fi, and in the absence of an obvious choice, Yamaha is my default when it comes to consumer grade electronics. In my experience, the Yamaha stuff gives decent sound on a budget. As far as reliability, they've all failed on me except for one manufacturer. I have NAD equipment that I've been using for 30 years that still works like new. They have AV options but it's a little pricey.