40+ year old motor run capacitors

[The Black Adder]

Hi all.

I've recently replaced some motor run capacitors in my reel to reel.

The old ones were made by Bosch and I think they date from 1973/75 from which I took from numbers printed on the side or each capacitor.

They are 10uf, 8uf and 20uf.

I was advised to replace them as they could leak. I can't see any leakage as such though.

Is there a way of testing them and if they still come up to spec, is it worth using them or should they be replaced anyway?

Thanks

[Wakefield Turntables]

Any cheap volt meter should be able to check resistance

[Firebottle]

Not so simple Andy. With high voltage capacitors you really need a high voltage tset to as a multimeter doesn't stress the cap enough.

[struth]

they need to be discharged and disconnected before testing(you might get a biggish spark if they have charge in them. short the terminals together with a screwdriver. leads are usually slide on)... an analogue meter is best. reading should go quickly towards 0 then drift up slowly. use a higish setting..10k range or so. you can use a digital one tho if all you have but i wouldnt.

[Jazid]

I've had a 500V oil filled polypropylene Bosch vent in a PSU recently. It was one of four, all looked clean before this. The other three measure perfectly up to 350V which is the limit of my test rig. I changed them all anyway, the mess wasn't fun to clean up, not worth the worry IMO. If they measure well at or near spec voltage you can always use them elsewhere but at an appropriately derated voltage?

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[struth]

yup, i'd be inclined to just change them too. can always keep for spares etc if ok.

[The Black Adder]

Cool, thanks guys.

I don't have any kit to test them. Would be interested in knowing if they are still up to spec though.

Changed them out anyway. Been advised to do so and I everything works fine.

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