When I turn on, in "protect" mode. I think the issue is with the power supply. It will cost $50 just to figure out what is wrong. Is it worth fixing? Can I replace the power supply myself? I know it is old, but I take care of my stuff and don't want to throw it out?
Nope, you can't do this yourself. Pay the fee for an estimate. If it is a fixable problem, the fee will be deducted from the repair costs. If you don't want to spend $50 on a receiver you don't think is worth fixing, then just start shopping for new.
Wendy, I had the 373 years ago, which came out around the same time. I found it acceptable at the time, but looking back I would now find it to be bright and grainy (I do remember what it sounded like). I myself would spend that $50 on another, more up to date model that has smoother sound and that will be more enjoyable for you to listen to.
Again, this is only my opinion.
For better advice, what speakers do you currently use?
Don't spend any money repairing an older receiver! Products nowadays are truly disposable. They cost more to repair then they are worth. problem is that after you make the repair, you are still stuck with an old receiver that could have something else go bad in a month. It is an older model that had middling power, & older surround technology. A new receiver will have dolby digital, DTS, & Lossless signal processing. Usually more power, & equal power to all channels. HDMI & Component video switching which didn't even exist back then. I just purchased a factory refurb Onkyo TX-SR606 for $315 with shipping and a 1 year warranty from accessories4less.com they have several models from Onkyo & Marantz. you can get the Onkyo SR506 for $200 with warranty. It will blow away what you have now with all the new decoders & HDMI. 75 watts per channel and Audessy to set up & equalize your speakers in your room! That beats spending $100 or more to fix your dinosaur.
I wouldn't spend money to fix to an A/V receiver. Like Scott said, they're (usually) very cheaply made (not saying they're crap, perhaps "mass-produced" would be a better term). They also become obsolete. For a couple hundred more than what it would cost to fix you could get a brand new receiver with more power that has decoders for all the fancy new HD audio formats.
I was an audio tech for 15 years so please believe what you read here.
Assuming that this unit has discreet circuitry, you will find that each channel has two output transistors tied to a large heat sink. Each transistor pair has a separate circuit that biases that set. This circuit comprises of several resistors plus other components that do that job.
The "protect" error means that one or more of the output circuits shorted. More than likely the output transistors were what shorted which also took out several of the resistors I spoke of which bias and provide the signal to the output transistors.
Assuming that you know how to check the outputs to find which one is shorted, you would then have to check the circuit components that feed that set of transistors. If you fail to replace even one defective component in that maze you will fry everything you just replaced.
Nope, don't even consider trying to repair that amp. Not only is it dangerous, but it is also a loosing battle.
If you want it repaired, pay to have it done. Otherwise, replace it. This is not a DIY job.