Working on a digital design M5. When I got the amp, the outputs were shorted and driver board bad. I removed all output, rail rectifiers and driver board. No shorted mosfets in the power supply but the amp is in protect. Pulled all the mosfets in the power supply. Not in protect. Relay turns on. I've isolated the problem to one of the power supplies. I can load all the others and the amp turns on. No protect. All driver transistors check good and drive signal looks good to the gates. When I load it with the mosfets, the power supply is immediately in protect. The mosfets do not get hot or short. Any ideas?
Hi Perry. No DC on the output filter. No outputs or output driver board in the amp. Rail rectifiers out of the amp. Protect light turns on immediately only when I load this one power transformer.Runs fine with the other 5 power transformers loaded.
Sometimes, one transformer will drive voltage to a circuit that could possibly either produce voltage that trips the protection or that powers a defective circuit.
Secondary of the power transformer is disconnected. The winding feeding the 12V regulators is disconnected. Still in protect.I don't see what else it could be powering.
I don't see what could be different between the two transformers if the secondaries are disconnected.
Post a photo of the component side of the entire main board and the component side of any driver boards if no one can help.
Post a photo of the component side of the entire main board and the component side of any driver boards if no one can help.
Here are the picks. Output driver board same as the Sun Down Audio SCV-7500D. Very similar to the Ampere 8 and AQ20 Sch. I'm only working on the power supply right now. There's nothing wrong with power supply driver board.
Attachments
Are the added white windings connected to anything? Or are their terminals simply loose, not even touching each other?
Does moving the shunt on the driver board make a difference?
Does moving the shunt on the driver board make a difference?
The white windings are for the +/- 15V rails. It is not hooked up at this time. I will use it to trouble shoot the output section once I get the power supply running properly.
No, changing the shunt makes no difference.
No, changing the shunt makes no difference.
I think you stated that you were only driving one bank of the supply at once but it appears that you're driving 5 banks in the photo. Is the photo what you currently have?
5 of the banks work. It's only one that causes it to go into protect. It doesn't matter if the others are loaded or not. I can take all the FETs out of the power supply. Load just the one giving me trouble and it will be in protect. I can pull the fets out of it, load the other 5 and the power supply runs. You might be able to see. I have the secondary pulled loose and the windings for the 12v supply pulled loose and it still puts it in protect if I load the transformer. I can't see how but it does. The fets do not get hot or short out.
You'll have to disable the protection circuit.
Which terminal, 1 or 7 of the 393 on the PS driver board is going high when the amp goes into protect?
Which terminal, 1 or 7 of the 393 on the PS driver board is going high when the amp goes into protect?
Does the 6th transformer have any small secondary windings? Other than the two windings that are in heatshrink?
Yes. The one I'm having trouble with has a winding for the 12V regulators. I have it loose also. So, it's not the issue.
Can you see any terminal of the driver board that has a different voltage when the 6th transformer is driven compared to when it's not driven?
Can you remove the driver board, if needed, and extend the connections so that you can work on it?
Can you remove the driver board, if needed, and extend the connections so that you can work on it?
