is anyone familiar with a flashing red protector light and how to find out what is causing it?
The 9090DB is a very nice unit, of course when it is working.
I have worked on quite a few 9090DB's, plain 9090's, and some 8080db's which are very similar.
The most common problem I have found in these units is bad fusable resistors on the driver board. The ones that "go bad" are the 150 ohm, 180 ohm, 10 ohm and 4,7 ohm
These are the small 1/4 w and 1/2 w resistors with a light colored body. They actually drive so far out of value that they cause the protect circuit to stay engaged.
While there can be other issues with these units such as bad outputs, and other problems on the driver board causing this problem you have.
If you are not familiar with electronics I would suggest you find someone who can do it for you that is qualified. If you have never worked on units such as this, you can actually cause a lot more problems, as well as getting hurt. The repairs typically require a soldering iron, Solder, Solder wick, Multimeter with Ohmeter, voltmeter and Ammeter functions and replacement parts. And after it is repaired, many times special cleaners and deoxit sprays are required to eliminate intermittancies in the controls and switches.
I am not sure of your location but I am in Brooklyn New York. If you are local I help you with the repair.
This is the output detection circuit sensing a fault. One by one eliminate the possibilities. With power off, volume at minimum, disconnect the speakers, carefully check that the speaker output terminals, top and bottom, are free of stray strands of wire, causing the short, turn on, check if light is still illuminated. Next, disconnect all inputs, check again, is the input voltage set correctly for your region? (110-120vac for north america). If all these easy fixes don't clear the light, the problem is internal. Cheapest fix, but least likely is a fault in the protection circuit itself, next cheapest is a bad power supply, the most expensive and most likely is one or more output transistors are bad (shorted or open, it is a fault condition). This is a non-user serviceable part, be sure to seek out a reputable tech with references. Do not throw this one away.
This is a highly collectable unit, it is arguably the best receiver Sansui made, it is worth something to folks even in it's broken condition. (Audiogon, Audio Asylum, eBay…)
I do vintage restoration and have worked on this model before, but only in the Lowell MA/Nashua NH area. I don't ship and I don't travel.
Probably a defect in the power amplifier. It could be any of several problems, from poor connections to shorted components.
If you are in the St. Louis area I can recommend someone that can help you with repairs.
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