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Help! I have been asked to try to fix a model 7885 (about mid 70's) PA mixer amplifier designed by GMS for (and built by) Gretsch. It has been fried. There are two bad power transistors, two bad voltage regulator looking things and a couple (if not more) cooked resistors. I have not been able to find any information on any of it. I downloaded data sheets for the two 2N3055 power transistors. I can't find any existance or history of the 642 or the GE 47828 voltage regulator looking things. I can't find a schematic so I don't know the value of the two resistors.
The good thing that urges me onward is the fact that the PC traces are all clean even though the other side of the board looks like it was hit by some sort of incendiary device. All of this damage is on the rear power supply and final section. The inputs and preamp section is on another board on the front of the case that looks fine.
Does any one have one of these or any information or history of having worked on one???
The good thing that urges me onward is the fact that the PC traces are all clean even though the other side of the board looks like it was hit by some sort of incendiary device. All of this damage is on the rear power supply and final section. The inputs and preamp section is on another board on the front of the case that looks fine.
Does any one have one of these or any information or history of having worked on one???
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