Are these the worst capacitors ever?

[boater sam]

I have huge stocks of components, gleaned from many sources over the years, some reputable, some not so.

Today I was modifying a Bush DAC90A and needed a 220uf capacitor. Drawer has plenty so I select a blue wrapped Philips electrolytic, Labelled 220 uT, 10v, 030K0  X4

I always test before fitting. Magic Chinese box says its a diode!   A resistance check shows a reading in k ohms, more one way than the other. So I test all 4 that I have in stock and they are all the same, quite useless as capacitors.

Are these known to be rubbish?

[Murphyv310]

Definitely no!
How old and for how long have they been stored? They may reform.

[Mike Watterson]

Try reforming with current limited PSU or resistor. An electrolytic that needs reformed will look a bit like a resistor and diode.

The worst are the plastic case two colour ones in later gear, mostly transistor.

[ppppenguin]

The contest for worst caps is a pretty open category. For small electrolytics the Philips blue ones are nowhere near that. Think Callins and the black/yellow/red Plessey horrors.

[boater sam]

I have never bothered to reform capacitors.  I can see that reforming 10v ones could be tiresome, what voltage would you start at, 1v?
What increments?  Ending at 10v?
Why would new unused but possibly long time stored capacitors test so badly as not to appear to be capacitors at all?  And why 4 out of 4 duff?

[Mike Watterson]

Just 10V via a resistor to limit current. Maybe 100 Ohms. Others may have better ideas. I'd never bother with attempting to reform the Plessey plastic case ones.

I've never used incremental voltages and reforming 250V ones on a 30V current limit PSU works unless they have dried out. Dried out ones usually don't pass current.

They must be very old. The oxide layer may not have been fully formed or gradually degraded.

[chriswood]

In my view the worst were from the capacitor scandal 1999-2003 with brands such as "Tayeh", "Choyo", or "Chhsi" they were the result of stealing formula for electrolytic caps which was wrong, See here https://en.wikipedia.org/wiki/Capacitor_plague
This was a result of a fraud/theft, at least with Hunts, Plessey, Philips etc they worked OK for a while and were more the result of low price and the technology of the time.

[Refugee]

It was called capacitor plague.
Loads of duff computer motherboards.

[boater sam]

I stuck all 4 together onto a current limited power supply, started at 5v for 10 minutes, then up to 10v for another 15 minutes.

Checking them after showed all were recovering capacity, one only 86uf, best was  134uf so it seems that they may reform.
I will probably discard them anyway.

[joebog1]

If they have started to reform, I would put them in the circuit they will operate in, and run the equipment for a few hours.
Saves you the trouble of faffing about with power supplies.

Blue Philips I have found to be very good. Not the best, but very good.

Joe