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Citronic PPX1600 oscillating 5mhz

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mikeydee77 View Drop Down
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Joined: 26 April 2023
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mikeydee77 Quote  Post ReplyReply Direct Link To This Post Posted: 07 May 2023 at 7:00pm
Well I have had a full day working on this amp but no success.   Once I got the board out  I did find a few grotty joints, replaced some of the wirewounds, removed the transistors and cleaned the grease of them, removed the triac - no impact in doing this at all. 

The only other clues that I have is that the oscillation will lose trigger on the scope (presumably jumping in frequency) when tapping the mosfets with a chop stick making me think it is either the devices or something in the PCB which has a few light toast marks on it.   Thanks for your help.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2023 at 6:24am
Have you checked the drivers and compensation cap/s? A problem there could definitely cause oscillation.


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mikeydee77 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mikeydee77 Quote  Post ReplyReply Direct Link To This Post Posted: 10 May 2023 at 6:46pm
Not sure I see any compensation caps...   Sorry... Can't figure out how to upload schematic or image unless hosted elsewhere?


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2023 at 7:02am
Ok, but it/they have to be there. Small ceramic around 150/220pf. Like I said, I don't know this amp, nor ever worked on one, so can't help any more.


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simonp1100 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote simonp1100 Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2023 at 5:57pm
Have you checked all the GROUND connections on the board & inside the amplifier ?.

Check the capacitors on the +15, 0, -15 supply & the output Zobel filters on each channel output.
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