Citronic PPX1600 oscillating 5mhz |
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mikeydee77
New Member Joined: 26 April 2023 Location: Bristol, UK Status: Offline Points: 9 |
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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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Earplug
Old Croc Joined: 03 January 2012 Location: Europe Status: Offline Points: 7216 |
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Have you checked the drivers and compensation cap/s? A problem there could definitely cause oscillation. |
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Earplugs Are For Wimps!
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mikeydee77
New Member Joined: 26 April 2023 Location: Bristol, UK Status: Offline Points: 9 |
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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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Earplug
Old Croc Joined: 03 January 2012 Location: Europe Status: Offline Points: 7216 |
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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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Earplugs Are For Wimps!
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simonp1100
Young Croc Joined: 01 September 2008 Location: Bristol Status: Offline Points: 1110 |
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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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