I repaired the PS of this amp - 8x IRF3205 and A1266 driver pairs with BD140 units. Amp powers and plays, but seems to drop into protect at very high gain/output. 1-ohm load, rated at 1000w at 1ohm. The amp draws about 70A from the bench and then falls into and then back out of protect. Thats probably only about 500w if that. Just before protect engages, the amp starts to clip.
Is this normal or is there something going on? I figured 1000w true (if it IS true) would pull over 100A from my bench.
Thank you
Is this normal or is there something going on? I figured 1000w true (if it IS true) would pull over 100A from my bench.
Thank you
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Understood. Actually I had forgot to turn on my bench ps. The amp was pulling down a Pb battery. It’s pulling up to 90ish amps now.... but I think there’s still a possible issue? The bottom waveform clips way before the top. Maybe this is why I don’t really care for class D. VDiv set to 5v. Probe at 10x.
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Not getting any vDC offset across +/- speaker terminals.. Maybe 0.100vDC at clip.
Even under NO LOAD, the bottom waveform clips before the top same as image above. I'm only seeing about 42vAC across speaker terminals. Checking rail voltage.....
Even under NO LOAD, the bottom waveform clips before the top same as image above. I'm only seeing about 42vAC across speaker terminals. Checking rail voltage.....
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Rail voltage is 126vDC directly across rect Anode and Cathode center legs. Output FETs are all seeing +-62vDC referencing RCA shield depending on the leg/fet etc. The FETs I am certain are seeing rail voltage.
So... Something is causing this amp to clip at about 40vAC at speaker terminals. I'd think there should be another 70ish AC volts on tap due to having such a high rail. Rail is not sagging under tests/load or no load more than 0.5vDC.
Where can I look from here? The class D output driver boards are quite busy.
Thank you
So... Something is causing this amp to clip at about 40vAC at speaker terminals. I'd think there should be another 70ish AC volts on tap due to having such a high rail. Rail is not sagging under tests/load or no load more than 0.5vDC.
Where can I look from here? The class D output driver boards are quite busy.
Thank you
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If you use one scope channel for the rails and the other for the output, do you see that much of a difference between the output and rail?
Test the 2 channels on the same point to make sure both channels are reading the same.
Test the 2 channels on the same point to make sure both channels are reading the same.
5vDiv. 10x on the probes. Reference is RCA shields for both probes. One probe on the rail directly at output FET set to DC on scope. Other probe on speaker terminal set to AC. I think shows a better story but does this look alright? Looks like a few volts shy of rail on both sides.
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Are the vertical amp 'cal' pots set to full clockwise for both channels?
This doesn't look like 50v/div. That would make the rail voltage about ±140v.
This doesn't look like 50v/div. That would make the rail voltage about ±140v.
Scope wasn’t calibrated but I think it is now. Cal was way off almost a factor of x2. Here it is again calibrated and showing at 20vDiv. Seems to be better matching now to my fluke 16 measuring +-63vdc rails. Perhaps this amp doesn’t need any more Dr Zeus vaccines.
