Wanted, info on Dubilier capacitor

[line sync]

Has anyone got any information on an electrolytic can capacitor made by Dubilier in 1948.
This is an 8+16uf 400v and is a drilitic type CR.
Alternatively if anyone has one of these capacitors I would like to know which connection is the negative (ground).
My Dubilier capacitor has leaked badly and the red/yellow spots to identify the connections have long since disappeared.
My capacitance tester cannot get a capacitance which ever way I connect it.
There is no wire going to chassis from the capacitor and no circuit diagram is available.

Robin

[Boater Sam]

Can negative is usual.
If it is reservoir and smoother with a choke or resistor between, the 8uf will be the reservoir.

[Jon_G4MDC]

No expert - but often the terminals had shapes pressed in the rivets and these were filled with colour.

If you can identify some shapes you might cross reference with another similar?

Just thinking out loud. Good luck!

[Argus25]

In many circuits the negative wire of the filter capacitor might not go to the chassis directly as it may be a type where there is a series power resistor in the power transformer's centre tap to develop a fixed bias for the output valve, agc and other circuits and occasionally the capacitor negative could be returned there. But with a meter you should find one of the capacitor's wires has a much lower resistance to ground than the other two.

That will leave you wondering which of the other wires is 8uF and which is the 16.

You have to disassemble the capacitor anyway to restuff it and you will see one foil assembly will be about twice the size of the other, you will also see the common negative too, most likely. So it should all be pretty obvious when you rebuild it which wire is which.

Probably, the size of the canister or case will easily accommodate 400V poly caps of the same uF value, if you use these you will never have to worry about it failing or leaking again. If it is a rectangular canister, a good way to mount these caps is on a rectangular PCB or phenolic board to insert in there.

[line sync]

Sam
Yes it does say "can negative" on the side of the can but there are 3 terminals and non of them are connected to the can.
This cap is not part of the main power supply which is on a separate unit.
Jon
This cap has got solid type terminals which are not riveted in the usual way so no squares and triangles stamped in the rivets.
Argus
You mention some interesting things so I'll make some checks and get back to you.
I will not be restuffing this can because it is corroding from the inside out but if all else fails I will open it like you say.


Robin

[line sync]

I did some resistance measurements today from the capacitor terminals to chassis and the lowest reading I found was 5k.


Robin

[Argus25]

Probably it would be better to transcribe the circuit from the set. I have done this for many TV sets and radios without schematics available. It doesn't take all that long if you print out the valve base diagrams before you start. Then it's very helpful in fault finding & restoration of the set.

If you don't want to trace the schematic, probably better then to open up your capacitor for repair & inspection. Probably best to insert three 8uF 400v poly caps in there and parallel two for the 16uF, if that will fit, if not use electrolytic caps. OLd electrolytics were so large often I have found I could put 600 or 630V poly caps of the same value inside their canisters.

If you scroll to page 7 of this article you can see how an array of poly caps can be used to restore a rectangular canister multi electrolytic cap:

http://worldphaco.com/uploads/HMV__904_ARTICLE.pdf

[Andrew B]

Hmm, corroding from the inside out? a 5K resistance to the can ground to the grounded pin? to be expected to read anything (or nothing) if the guts have corroded away inside.