I talked with PapaZBill about this a long time ago and he suggested I start a thread. So here it is.
I've repaired this amplifier 3 times now. Every time it ends the same. Amp performs well. Amp dies at random. The first time is lasted a month. The second time, it lasted a week. The third time I decided to use it in my own vehicle to rule out 3rd party issues/abuse and subject it to an automotive environment. Perhaps witness it myself. It beat the brakes off my LMS 15's for nearly a month. Then one day, The moment it powered on - the PS popped. The track hadn't even loaded yet so it was signal free. The failure is always with one of the N channel devices. Never the same one really. I have used 3 different parts here. The 640, the 640n and 31n20d. I don't believe they're the cause of the problem. I've subjected this amplifier to high stress situations, lots of measurements, and every twist imaginable. I have not been able to replicate this failure mode on my bench. I was hoping someone knew something I don't to make this repair a 4th - and final - time.
Board is pictured. Thanks in advance.
I've repaired this amplifier 3 times now. Every time it ends the same. Amp performs well. Amp dies at random. The first time is lasted a month. The second time, it lasted a week. The third time I decided to use it in my own vehicle to rule out 3rd party issues/abuse and subject it to an automotive environment. Perhaps witness it myself. It beat the brakes off my LMS 15's for nearly a month. Then one day, The moment it powered on - the PS popped. The track hadn't even loaded yet so it was signal free. The failure is always with one of the N channel devices. Never the same one really. I have used 3 different parts here. The 640, the 640n and 31n20d. I don't believe they're the cause of the problem. I've subjected this amplifier to high stress situations, lots of measurements, and every twist imaginable. I have not been able to replicate this failure mode on my bench. I was hoping someone knew something I don't to make this repair a 4th - and final - time.
Board is pictured. Thanks in advance.
Attachments
Does twisting the inductor or flexing the board change the idle current?
Are there any solder connections (especially in the drive area) that aren't clean that could be intermittent?
Have you tried heating and cooling various areas of the circuit to see if that caused any problems?
Were the parallel FETs matched?
Are there any solder connections (especially in the drive area) that aren't clean that could be intermittent?
Have you tried heating and cooling various areas of the circuit to see if that caused any problems?
Were the parallel FETs matched?
Pay special attention to the DC voltage across the 12v Zeners for the drivers, when you heat/cool them.
Because the output inductors look to be firmly in place, you may not be able to flex them enough to cause idle current to rise.
The sleeves on the inductor leads become perforated due to heat and vibration and may be rubbing against adjacent turns.
Whenever we get amps in with this type of sleeve, we replacing them with the sleeve pictured below.
The 12 volt Zener's in the annotated white boxes should be checked as Perry suggested.
The sleeves on the inductor leads become perforated due to heat and vibration and may be rubbing against adjacent turns.
Whenever we get amps in with this type of sleeve, we replacing them with the sleeve pictured below.
The 12 volt Zener's in the annotated white boxes should be checked as Perry suggested.
Attachments
Is there current limiter or just gate protection.
Either way possibly diodes or Zener's test ok but have been damaged
with multiple output failures either gate zeners or diodes if limter
. or numerous components damaged from failure
like limiter clip detect etc etc tied to the output , but still works regardless
with damaged componets . till amp gets hot and has odd current wars.
does DC on output drift oddly with high temp. could be current sources
with bad connections or drifted parts. or coil / caps with broken leads
and not all visible. as in lead connections not visible on top , bottom of board
looks soldered. but actual lead broken on component hidden.
Either way possibly diodes or Zener's test ok but have been damaged
with multiple output failures either gate zeners or diodes if limter
. or numerous components damaged from failure
like limiter clip detect etc etc tied to the output , but still works regardless
with damaged componets . till amp gets hot and has odd current wars.
does DC on output drift oddly with high temp. could be current sources
with bad connections or drifted parts. or coil / caps with broken leads
and not all visible. as in lead connections not visible on top , bottom of board
looks soldered. but actual lead broken on component hidden.