Hi guys, I have a G22000 under restoration that I feel like simply does not want to live. Little background, when it came in right channel of the amp out, left "worked". Found the power supply for the right channel had out of spec resistors that looked really crusty, along with bad regulators. Specifically R08 and R16 which are in series with the driver board rails. Replacement brought the channel back, recapped the driver board and the power supply and sounded great.
Both channels worked now so recapped the left channel and left channel power supply. After the left channel was recapped noticed what sounded like low frequency oscillation. Ran function generator into channel and noticed under 100hz or so the distortion was terrible, then...smoke, R33 and the resistor on the back of the driver board smoked and burned taking out the outputs. Both amps were biased fine. So now I am thinking it is something what was replaced so have gone back through and checked every part replaced and not finding anything wrong. When I take voltages on the left channel power supply I get a higher then normal positive rail. Looks like normal should be around 82vDC, I am getting 94-95vDC. This amp is rather confusing in how the rail comes off the power supply to the driver board, back to the power supply. If I power the unit with the driver board in, the resistor R33 on the driver board starts to smoke.
The B+ rail of 94-95vDC I am reading with the driver board out. I am comparing it to the working side and it is higher and never reduces to a little over 80v which it seems it should. Any tricks to pin point the short or part that is drawing excessive current? I am thinking the driver board is a victim of the power supply having an issue down stream. Something notorious for failure on the board I am missing?
Thank you in advance for any help!
Both channels worked now so recapped the left channel and left channel power supply. After the left channel was recapped noticed what sounded like low frequency oscillation. Ran function generator into channel and noticed under 100hz or so the distortion was terrible, then...smoke, R33 and the resistor on the back of the driver board smoked and burned taking out the outputs. Both amps were biased fine. So now I am thinking it is something what was replaced so have gone back through and checked every part replaced and not finding anything wrong. When I take voltages on the left channel power supply I get a higher then normal positive rail. Looks like normal should be around 82vDC, I am getting 94-95vDC. This amp is rather confusing in how the rail comes off the power supply to the driver board, back to the power supply. If I power the unit with the driver board in, the resistor R33 on the driver board starts to smoke.
The B+ rail of 94-95vDC I am reading with the driver board out. I am comparing it to the working side and it is higher and never reduces to a little over 80v which it seems it should. Any tricks to pin point the short or part that is drawing excessive current? I am thinking the driver board is a victim of the power supply having an issue down stream. Something notorious for failure on the board I am missing?
Thank you in advance for any help!