This is a nice-sounding unit which I only wish would work more reliably :P It will play for a certain length of time - sometimes hours, even days, then, with a small, audible *pop*, the audio output will cease, though the unit remains powered on. Flicking it on and off will usually bring the sound back, but is not a lasting fix.
This seems to be happening more and more frequently. I have soldering and electronics experience and can go poking around inside if necessary. Whatever it takes to get it to work, short of replacing it...
Any theories or suggestions for this problem? Your help would be greatly appreciated!
without being an expert on the subject... my 1ST guess would be that you're listening louder and louder and triggering thermal protection circuit breakers or something to that effect. have you recently made a gear change that affects air circulation to your amp?
other than that... something is definately wrong. try backing off the volume a few notches to see if it stops turning off.
hmm. interesting. perhaps the amp's internal protection or something is being falsely triggered. the amp is usually kept at a very reasonable listening volume and is well ventilated.
how's internal temp measured on these? thermistors? I could take a look at those if I can find any on the board. maybe replace one with just a resistor if it has gone bad ;)
when you start getting into circuits... you lose me. i know what capacitors and resistors do and what coils do (to audio signals at least... well they turn AC into DC too in transformers) but that's about it.
if you feel confident enough to replace transistors... then you should be able to test your gear.
try to find j vigne... he's really saavy in these highly technical questions. the most technical thing i could do electronically is use thiele small parameters to design a speaker and use crossover circuit templates (and math tables) to build a crossover.
if you're listening at reasonable levels, then you're not "circuit breaking" i'd think unless your pretection is broken. when i say "thermal protection" i'm ONLY repeating a word that i've read a few times. LOL i don't know exactly how it works or if cheaper gear like sony even has it.
try checking your cables for shorts. along similar lines, when my subwoofer driver was mounted outside it's cabinet, one of the cables came lose and shorted out (at 20 minutes of low volume) causing my NAD reciever to flash brightly and literally start burning in what looks like a cracked capacitor. that's my only real experience with amplifiers and thermal LOL.
budget minded - you are much smarter than you give yourself credit for ;)
I fixed the amp in two minutes and here's how I did it: Upon cracking it open a second time, this time with an idea of what I was looking for, I found two thermistors - one each screwed down to two of the four large amplifier transistors at the big heatsink. I decoupled them from the transistors, screwed the transistors back down securely to their thermal pads, then used some spare wire to ground the thermistors together to a screw on the main board. They are now not measuring the temperature at the heatsink, but just the internal temperature of the unit
One of the thermistors may have, with time, become a bit too sensitive, causing the amp to shut down prematurely. Also, in its old age, the amp could simply be putting out a lot more heat than it used to. That would be a bad thing ;) Perhaps I should scrape off the old thermal pads and replace them with Arctic Silver V? For now, I put a fan on top to keep it cool, and we'll run it until it dies. ;) It has been rock solid and sounding just like its old self again.
There's not much "poking around" to be done with today's receivers. With the number of IC's utilized in their circuitry, there are too many components that cannot be tested indivdually as in the days of discrete components. We are talking about large scale circuits that operate on the milliamp level, so unless you have some fairly sophisticated test gear and a soldering iron that can resolder a 128 pin IC without burning it up or shorting it out and a schematic that you can read, you are best leaving this repair to a technician who has access to both. This could be as simple as a bad power switch, but there's no way to "poke around" that idea other than bypasing the switch or replacing it. "Engineering" solutions when you don't know where to start is not the best route in this instance, in my opinion.
The best thing you can do at this point is to try to isolate the problem in terms of what triggers the situation. As has been suggested, the best way to start is first consider whether anything in the system changed just before this problem first appeared. Secondly, disconnect all inputs and outputs from the receiver and run it with just the tuner playing into one set of speakers. Add more inputs to the receiver until you trace to a component or situation that causes the unit to react. Of course, the most obvious thing to check is how hot the unit gets in "normal" operation and then in a "distress" situation. If this is a purely random problem in that the unit demonstrates the complaint even when hooked to just speakers and tuner, then the best you can hope for is taking it to the best technician you can find (Sony has regional service centers that I would send it to) and hope for the best. This could be a typical problem Sony is aware of in this model.
Random, intermittent problems are very difficult to trace and repair since a technician has a difficult time finding a problem that may only show up after days of operation. If they are not standing in front of the unit at the moment it shuts down, they might have to start the procedure all over again. Same goes for checking their repair. There are some techniques a repair person can use to encourage intermittents, but that isn't always going to work on each piece of gear. Ask for an estimate of reapir costs and decide whether this receiver is worth saving.
Otherwise, the next best answer is to continue to flick it on and off.
Jan, no receiver uses a 128 pin ic this would be a very large scale integrated device, which is only used in a pc. This type of ic would have 64 pin inputs and 64 pin outputs. Good quality ss amps used in good quality receivers such as Nad and HK do NOT contain integrated circuits anywhere in the amplifier signal path. They are in fact discrete amplifier sections, containing seperate capacitors,resistors,transistors with no ic's such as integrated op amps anywhere in the amplifier sections. The amplifier sections are also not controlled by ic's, but by relays and switches directly linked to the power supply. The only ic's that are used in a good quality receiver are for digital surround decoding. In this case a 24 bit ic is the standard for most models with a 32 bit processor used on some upper end models.
ER - I believe even in this Sony receiver a large scale systems management chip would be used. This controls enough functions that it could, or might, be a possible cause for shutting down on a vry intermittent basis. This could be 64 or 128 pin. I honestly don't know. None the less, the ability to diagnose and repair large scale IC's would be required before I would suggest anyone attempt "poking around" in a contemporary receiver. That was my point.
