These are a nightmare to fix and pop their output devices almost instantly if you short a speaker lead. I have worked on SA-12 and SA-100, but not specifically the SA-220.. If someone has the parts to fix this amplifier that is a miracle, but I can't say whether spending that kind of money on one of these amplifiers is worth it.
The output devices do have to be very closely matched and the originals are no longer made. Someone at some point had identified substitute devices that if matched would work ok.. I no longer have the information unfortunately.
Have you checked all of the internal fuses. The SA-12 the one I have worked on most recently had 3 fuses per channel - I suspect the SA-220 is not too different and if you are very lucky one or two of those have blown and the output devices might be ok. (not that likely)
Never, ever allow the speaker leads to short, even for a moment as that is all it takes to blow the outputs if signal is present on the outputs. The fuses do not blow quickly enough and the mosfets self destruct. If you have one bad fet you should replace all of them. The devices under short conditions grossly exceed the safe drain to source current rating even at very low signal levels and melt...
The output devices do have to be very closely matched and the originals are no longer made. Someone at some point had identified substitute devices that if matched would work ok.. I no longer have the information unfortunately.
Have you checked all of the internal fuses. The SA-12 the one I have worked on most recently had 3 fuses per channel - I suspect the SA-220 is not too different and if you are very lucky one or two of those have blown and the output devices might be ok. (not that likely)
Never, ever allow the speaker leads to short, even for a moment as that is all it takes to blow the outputs if signal is present on the outputs. The fuses do not blow quickly enough and the mosfets self destruct. If you have one bad fet you should replace all of them. The devices under short conditions grossly exceed the safe drain to source current rating even at very low signal levels and melt...
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