This is a new one for me, the 470uf 100v and 2200uf 80v caps for the negative rail vented.
I've read this can be caused by bad drive but am unsure if that'd be in the PS or output section.
Right now I have the rectifiers and vented caps removed, no other changes. How would you go about fixing this one?
I've read this can be caused by bad drive but am unsure if that'd be in the PS or output section.
Right now I have the rectifiers and vented caps removed, no other changes. How would you go about fixing this one?
Replace them and let the amp idle. Do they heat up?
Measure the positive and negative rail voltage and confirm that are of equal magnitude.
Then drive signal into the amp (speaker or load connected) and see if the negative rail becomes greater in magnitude of the positive rail.
Measure the positive and negative rail voltage and confirm that are of equal magnitude.
Then drive signal into the amp (speaker or load connected) and see if the negative rail becomes greater in magnitude of the positive rail.
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The best I could do is a pair of 1000uf 80v caps. Will that be sufficient for testing or should I put it back on the shelf for now?
Decided to just give it a go.
Changes:
2x 1000uf 80v caps installed in place of the vented caps.
Rectifiers reinstalled
The caps don't seem to be getting hot but I didn't run it for very long, just enough to probe the output gates and measure rail voltage.
Both rails are sitting around 50v dc, within a few 1/10s of a volt of each other.
There's an issue with the output section drive I'll need to sort out before continuing. Faint clicking buzz from the board and a dc pulse on the output gates.
I'll report back with my results of your 3rd step after getting the output drive sorted.
Thanks Perry
Changes:
2x 1000uf 80v caps installed in place of the vented caps.
Rectifiers reinstalled
The caps don't seem to be getting hot but I didn't run it for very long, just enough to probe the output gates and measure rail voltage.
Both rails are sitting around 50v dc, within a few 1/10s of a volt of each other.
There's an issue with the output section drive I'll need to sort out before continuing. Faint clicking buzz from the board and a dc pulse on the output gates.
I'll report back with my results of your 3rd step after getting the output drive sorted.
Thanks Perry
That's what the last step was to determine. When you have bad drive for 1/2 of the outputs, the ones with the bad drive typically cause excessive voltage to build on their half of the rails. The problem could be the driver transistors or the low-side of the 2092.