Long story in short.
Amp came in for repair. Outputs were fine, but the driver boards needed rebuild. Done.
Amp powers up, but the outputs are getting hot and the current draw increase at idle rapidly.
Now this got me confused a lot....
If i play some tone thru the RCA at max gain without a load, amp just draw 1A stable....lowering the gain increases the current draw and vice verse - increasing the gain lowers the current draw.
What is going on ? Why the sinewave amplitude affects the current draw without a load, this does not seem right.
I've tested almost everything - diodes, resistors, bias transistors D1859, outputs, checked for solder bridges, even recapped the bloody thing.
Rail voltages and aux voltages are OK, no issues there. Is this an issue with the biasing ? There are 2 resistors across the bias transistor, if i'm being right they, the ratio between them sets bias Ic ? And there are no emitter resistors but diodes in the output section after the outputs ? I'm confused.
Any ideas ?
Amp came in for repair. Outputs were fine, but the driver boards needed rebuild. Done.
Amp powers up, but the outputs are getting hot and the current draw increase at idle rapidly.
Now this got me confused a lot....
If i play some tone thru the RCA at max gain without a load, amp just draw 1A stable....lowering the gain increases the current draw and vice verse - increasing the gain lowers the current draw.
What is going on ? Why the sinewave amplitude affects the current draw without a load, this does not seem right.
I've tested almost everything - diodes, resistors, bias transistors D1859, outputs, checked for solder bridges, even recapped the bloody thing.
Rail voltages and aux voltages are OK, no issues there. Is this an issue with the biasing ? There are 2 resistors across the bias transistor, if i'm being right they, the ratio between them sets bias Ic ? And there are no emitter resistors but diodes in the output section after the outputs ? I'm confused.
Any ideas ?
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Shorting emitter to collector ?
Perry - yes. My small lab. power supply is 10A max...and even mounted into the heatsink, amp draws 10A max after 7-8 seconds of idling and then laboratory power supply protection kicks in. I do not really want to hook it up at my bigger power supply...
Have you contacted Gordon ad The Amp Doctor? He built these amps.
The Amp Doctor - Servicing your amp!
The Amp Doctor - Servicing your amp!