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FDP Forum / Fender Amps: 1985 - Current / Cyber Twin power supply noise



Jul 17th, 2018 02:42 PM   Edit   Profile  

I seemed to have a 60 or 120 hum suddenly appear. From what I understand, that's most likely a capacitor near the power supply. I have disassembled the whole thing. It's a head, not a combo. I ordered a cap tester from Amazon for this project ($30). I've never used one but it looks straightforward enough. When I got the main board out, I noticed that a 450V, 22uf cap was loose. The anode was completely corroded off. problem found. I went ahead and tested the rest of the caps in the vicinity of the power supply. I found another one that wouldn't give me a reading. It's fortunate that it's also a 450V, 22uf cap. I ordered some on Amazon because there are no longer any electrical supply stores in Reno.
I've never replaced amp caps before. Am I getting the right ones? does the +/- rating matter for this application?


Too Near Atlanta GA

Amp Tech Emeritus
Jul 17th, 2018 08:32 PM   Edit   Profile  

The OEM parts (C127, C125, C143 and C148) are 22uF 450 VDC 20% tolerance. The one's you ordered should be okay, I would have suggested ordering from Mouser Electronics for a higher quality cap, but those should be okay. Be very careful unsoldering the defective caps and any residue or lead clippings left behind...as well as installation of the new caps. You have very sensitive PCB pads, high voltages and static sensitive digital/solid state components in that amp. We always disliked servicing the cyber series amps. Good luck and be careful.


FDP Forum / Fender Amps: 1985 - Current / Cyber Twin power supply noise

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