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The Schaffner model FU

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TerraHertz:
This is just part of a rather painful saga. Recently arrived: two HP 8118A pulse/data generators. The first known to power up but turns out to have a CPU board badly corroded by a leaked NiCad, the second clean but has a dead power supply.
So obviously, put the good PS in the clean machine.

I suppose I'd better mention that due to dismay on discovering the unit 1 corrosion, and so never powering it up, I had neglected to switch it to 240V. Even when installing that PS in unit 2. So there were initial fireworks provided by three MOVs going bang. But no other damage. Replaced them, switched to 240V, tried the PS by itself - OK. Plugged it in and the machine runs. Yay!

Runs for about two minutes before going bang again. Except this time the stinky RIFA smoke kind of bang. Huh? But I'd changed the one RIFA cap on the board already! Where did the smoke come from?

Ladies and gentlemen, may I present you the Schaffner model FU mains filter.
AKA brick of unrepairable stinky RIFA death.

So, apparently it contains at least one RIFA cap which couldn't take 240VAC. I opened the soldered-on lid, hoping to be able to melt out the potting material and repair/replace the contents. Previous metal case mains filters I opened had used tar for potting.
Nope, it's a tough epoxy.

Hmm... well the 2nd unit seems newer. Same custom mains filter but it looks like a later manufacture. Maybe they'd stopped using RIFA caps?
Let's see. I set it up by itself on a bench with mains applied. Let it sit for several hours. No bang.

OK, perhaps it will be OK. I installed it in the power supply. The machine runs again. And then half an hour later goes bang. This Schaffner FU has blown a RIFA cap too.

Great. So now I have two blown, unrepairable mains filters, of a special shape and with custom mounting screws. Fantastic.

FU Shaffner and RIFA.

madires:
Unfortunately a common problem with the old Schaffner line filters. From what I know they used Rifa caps until mid or end 90ies. Maybe you can improvise a mounting adapter with a piece of aluminium sheet.

floobydust:
KEMET (Vishay) is still selling those shitty Rifa capacitors PME271 series. We should file a class action lawsuit against them as they are proven kak. Even a Volkswagen-situation where Schaffner and Rifa/Vishay/KEMET know the parts are failing but stay quiet about it- is Schaffner still using them??!?

With age, I find the resin case cracks and surely mashes the paper inside. It's interesting that they fail even when potted. Modern PME271 250VAC parts are tested to 3,000VDC once.
All you can do is email Vishay/KEMET and point it out I guess. Because the caps are used for EMI, there must be some manufacturers afraid to design them out, so they are around to this day.

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