Mains transformer secondary filter cap failure

Not really except maybe a voltage spike or old age or poor qality control....

Theoretically, I suppose a partially shorted primary could result in excessive voltage on the secondary before a fuse blew but since it works fine, assume it was just a random failure.

--- sam | Sci.Electronics.Repair FAQ:

Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs.

Nigel,

I've seen such a failure in one or 2 models of old NAD receivers. In those cases, I think the capacitor just failed. I never found any other problems with the amps.

Regards, Tim Schwartz Bristol Electronics

and

control....

excessive

assume

is

in the

No maker's name on the cap, its original colour and appearance, but audio amp is only 3 years old, very expensive 350W one. Hopefully just a failure you would normally expect to show itself before factory final test.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Is that 100V. RMS? So about 140V Peak, 280V P-P...I'd replace 400V, if it'll fit.

How old?

and

nearer 2x55V ac so 110V RMS The only marking is

no mention of ac or dc so could be 200V dc, maximum dimensions about 8x10x4 mm, I will crack open at some point.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Mains transient. I'd never use a 200V cap there.

Graham

I expected the problem to be near the pins which are about half way along the foils, staggered for the pin spacing. Problem was buried in the assembly about 3/4 into the centre, a number of sputtered/fused layers but no smoke emanation. There was localised micro ruffling of the foil in that area whether cause or effect of localised heating , I don't know, but the ruffling extended the width of the foil, not just the small "spot weld" area.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on