Someone sent me this Skar amplifier to look at, the design looks eerily similar to Audiopipe, especially the output stage. But I digress...
Arrived with the power supply section completely nuked so I rebuilt that. the output stage appeared to be fine.
When the PCB was bare on my bench, the amplifier runs fine and produces proper audio. No excessive current draw.
Once it was reinstalled in the chassis, power-up resulted in an insane current draw with the threat of blowing up the power supply section again. That must have been what took it out the first time. After tinkering around, it appears the issue occurs when the two grounds are brought together (they come together at one of the two chassis PCB mounting screws). Basically, the secondary and primary grounds when brought together is what causes this scenario.
Once i isolate the two grounds again, the amp will run fine.
The two grounds are already coupled together through the PCB itself with a resistor/capacitor network in parallel which actually starts to smoke when the amplifier is in fault mode.
I have been over this thing, and I cant find anything. I am at a loss. Only thing I can assume is the output stage is going into latchup or something. protection light also is orange.
Ideas?
Arrived with the power supply section completely nuked so I rebuilt that. the output stage appeared to be fine.
When the PCB was bare on my bench, the amplifier runs fine and produces proper audio. No excessive current draw.
Once it was reinstalled in the chassis, power-up resulted in an insane current draw with the threat of blowing up the power supply section again. That must have been what took it out the first time. After tinkering around, it appears the issue occurs when the two grounds are brought together (they come together at one of the two chassis PCB mounting screws). Basically, the secondary and primary grounds when brought together is what causes this scenario.
Once i isolate the two grounds again, the amp will run fine.
The two grounds are already coupled together through the PCB itself with a resistor/capacitor network in parallel which actually starts to smoke when the amplifier is in fault mode.
I have been over this thing, and I cant find anything. I am at a loss. Only thing I can assume is the output stage is going into latchup or something. protection light also is orange.
Ideas?
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This is most commonly caused by a shorted transformer (possibly intermittently). Twist/push/pull on the transformer to see if you ever read 0 ohms.
If not, scope the secondary ground to see what's causing the resistor to see voltage and overheat. If it's AC (square wave), you'll have to chase it down.
If not, scope the secondary ground to see what's causing the resistor to see voltage and overheat. If it's AC (square wave), you'll have to chase it down.
Thats what I was thinking was a shorted transformer, but I am not physically seeing it on the multimeter, i will likely have to take a different approach.
The fault is only there if i ground the two, otherwise it runs fine with no smoking.
I did try and measure DC voltage between the RCA ground (secondary) and primary ground, its 0 volts. However at one point a minute ago, when my meter probe on the RCA ground touched both the RCA and Chassis ground at the same time, i got a spark which was very strange. (the RCA and Chassis are 0 ohms, grounded as before) so it doesnt make sense.
I will scope the secondary as you suggested and see whats going on, I hope.
The fault is only there if i ground the two, otherwise it runs fine with no smoking.
I did try and measure DC voltage between the RCA ground (secondary) and primary ground, its 0 volts. However at one point a minute ago, when my meter probe on the RCA ground touched both the RCA and Chassis ground at the same time, i got a spark which was very strange. (the RCA and Chassis are 0 ohms, grounded as before) so it doesnt make sense.
I will scope the secondary as you suggested and see whats going on, I hope.