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(Older) Trace Elliot tuning ports?
- Thread starter PhatBasstard
- Start date
I could be wrong, but......
My GP12SMX has the AH250 power amp output stage. I too, read about the "star washer" issue and got me to have a poke about inside. I noticed...
Yes, there is chassis ground that I took off the screw to. There WAS a star washer there. It did look a little oxidised, so i sanded the chassis top and bottom (to get off the paint) and put 2 new star washers, against both sides of the chassis.
I now realise that my 1994 model has the MOSFET amp and not the "BiPolar Bear" amp. Appears that the "Bipolar Bear" amp was an aptly named bipolar transistor design. When MOSFETS "blow" or thermally and/or electrically go supernova, they go in an "open" status and theoretically nothing goes to the speakers. When the BiPolar design melts, it "goes DC" and sends unfiltered 60Hz through your speakers, destroying them.
I had an old PEAVEY centurion bass head that did this to me twice (went DC- output capacitors fried) , but thankfully it didnt kill my 2x15 sunn bin. After the second time it went into the dumpster.
I'n not an expert, I just know what mosfets look like from being a radio shack nerd a century ago.........
My GP12SMX has the AH250 power amp output stage. I too, read about the "star washer" issue and got me to have a poke about inside. I noticed...
Yes, there is chassis ground that I took off the screw to. There WAS a star washer there. It did look a little oxidised, so i sanded the chassis top and bottom (to get off the paint) and put 2 new star washers, against both sides of the chassis.
I now realise that my 1994 model has the MOSFET amp and not the "BiPolar Bear" amp. Appears that the "Bipolar Bear" amp was an aptly named bipolar transistor design. When MOSFETS "blow" or thermally and/or electrically go supernova, they go in an "open" status and theoretically nothing goes to the speakers. When the BiPolar design melts, it "goes DC" and sends unfiltered 60Hz through your speakers, destroying them.
I had an old PEAVEY centurion bass head that did this to me twice (went DC- output capacitors fried) , but thankfully it didnt kill my 2x15 sunn bin. After the second time it went into the dumpster.
I'n not an expert, I just know what mosfets look like from being a radio shack nerd a century ago.........
