Caps - worth?

[Diabolical Artificer]

I've found a few of these caps in the shed and doubt I'll ever use them. I presume they're paper in oil. Apart from the Sprague pictured most are small value, around 2.5u like the TCC pictured and lower.

Firstly would they of be any use to anyone and secondly, reasonable price?

Andy.

[Humber888]

They certainly look like old sealed paper-in-oil capacitors. I can't see from your picture, but the terminals are normally fitted to ceramic standoffs. These seem to be pretty reliable but its worth checking them for value and also leakage at their working voltage. Not worth more than a few £s at most as you can buy modern polypropylene motor start capacitors quite cheaply. Have you got the mounting clamps for ones without them already soldered on?

Mike

[paulsherwin]

Do any of the audio people believe them to have magic qualities?

[Radio Wrangler]

It sounds like you have little to lose and potentially something to gain. Pop them on an auction site. Setting a starting price might limit people's imaginations. Measure and quote the leakage currents at rated voltage as well as measured capacitance. Discharge carefully after leakage testing. Good ones can hold charge surprisingly well and even self-charge from air motion past the terminals. I once bought a 20uF 3kV photoflash block capacitor that had been stored without its terminals wired together, and being a fully paid-up coward shoved a screwdriver across the terminals before handling it. Pow! so wire the terminals together before shipping.

Oh and add photos of the terminal insulation.

David

Do any of the audio people believe them to have magic qualities?

Oh yes, 10 in parallel for cathode decoupling work very well. That is 20 for a stereo single ended amplifier (or two monoblocks), they turn out to be twice the size but what is good hifi worth?

[turretslug]

Certainly, the Sprague one with its DC rating and reasonable capacity ought to attract a few bites- thinking of those who like to run medium power triodes of the 300B ilk close to their ratings where electrolytic types' voltage margins are getting left behind. It looks in good cosmetic nick and "PIO" seems to be almost talismanic in some circles.

[G6Tanuki]

My only angst relating to selling these on would be legal, and based around whether they contained PolyChlorinated-Biphenyl 'oil'.

https://en.wikipedia.org/wiki/Polychlorinated_biphenyl

[Skywave]

Believe it or not, in 1972, I was working with equipment that wasn't that old then - doing maintenance on HV power supplies which used that type of capacitor. Yes, I'll believe that the contents of them could be harmful to humans and the environment, but I don't recall any concerns being expressed then. Perhaps, all those years ago, that was just due to ignorance and lack of research - or maybe not.

As for the legality of selling them, isn't that simply a case of 'buyer beware'? The seller has no control over what the buyer does with them.

Al.

[Diabolical Artificer]

Thanks for your input. Had a quick look on line, there seems to be quite a market for PIO caps for guitarists wanting "that" tone, bumblebee and other types as used by Gibson circa 60/70. I'll pop them on ebay after testing.

What sort of equipment would they have been used in? The only thing I have that uses a similar capacitor is a Marconi distortion analyser. So maybe test equipment,HT supply and motor control?

Andy.

[M0FYA Andy]

Block capacitors of this type were used extensively in military equipment, where reliability under all environmental conditions is paramount.
Andy

[Diabolical Artificer]

So Andy, decent caps then, which my testing bears out.

I tested these today and was really surprised how good the results were compared to NOS electrolytics of comparable age that I've "reformed".

The neon that indicates leakage on my reformer didn't light once and the leakage current was very low on the way up to max voltage and the final leakage was near non existent. The Sprague was 3uA and the TCC .1uA

Andy.

[Andrew B]

Hi Andy.

The TCC ones in the grey cans used to be very popular in surplus electronic shops, some up to 8uF and 1000VDC. I always thought they were wax/paper construction, some had "Viscogel" or similar written on them, nearly all had ceramic stand-off connectors.

They usually came in a waxed cardboard box, with a date accepted into stores etc. Many were ex WW2, I used to find them in power supplies or more often, on their own in said boxes.

There are some on an auction site starting at 30 quid!!!

Audiophools will love them.

[Wendymott]

One of my "late" friends , whom was an "ex Ex gov" dealer, but also an audio enthusiast... I will not use the Term used above as a mark of respect....but his Crossover networks were something to behold, using NO Iron inductors and oil filled caps as described above...we have lost a lot in modernisation...... Ferrite cores in crossovers Electrolitics Jack would be "spinning"......