Capacitor Test & Reformer

[PJC58-Hythe]

I decided it was time to I had a capacitor tester & reformer that could test leakage and ESR so I set about designing one. I used a freely available circuit from the Internet for the ESR tester and my own design for the leakage and reformer. I laid out a PCB as I really don't like having this sort of thing on strip board. I'm just waiting for the transformer to arrive from Primary Windings so I can complete it. It's been fully tested using a physically much larger transformer I had lying around.

On the ESR tester I decided to bring the calibration control out to the front panel as this allows calibration when using different length test leads.

[Vintage Engr]

That looks really good, very professional, well done.
Useful to have the ESR meter built in with the reformer.
I look forward to seeing it when its completely finished.

David.

[stevehertz]

All I can say is 'wow'. Brilliant. I want one.

[Horris]

Great piece of equipment. A credit to you.
Any chance of a circuit please?

Dave

[Sinewave]

I've been meaning to make one of these. Years ago I did start acquiring parts and I probably have a transformer somewhere which will suit. I've got too many projects on the go!

[G6fylneil]

I'd be embarrassed to post a picture of my capacitor reformer, someone would say "thats just a capacitor and diodes robbed out of CFL light bulb ..." but in conjunction with a variac and a couple of Flukes and (sometimes) an isolation transformer, it's worked well for many years. And done something useful with those CFL lamps that were given away years ago.

[Cathovisor]

Looks to be a useful device.

Does it "pulse" the DUT whilst reforming like the much sought-after "Reforming Unit, Electrolytic Capacitor No. 1" does? What happens if the DUT goes short whilst reforming?

In the past all I've done is simply apply a steadily increasing voltage from a HT PSU with a milliammeter in circuit whilst keeping an eye on proceedings but that can be a bit laborious. I did once harbour the idea of applying a constant current to a cap (say, 2mA), the source voltage of which would be limited to the maximum working voltage. The idea never progressed, needless to say.

[PJC58-Hythe]

I eventually got around to labelling the meters and have now used the device 'in anger' so I'm happy it works as it should. Should anyone want to build it I have attached the circuit, please note the FET needs to be on a heatsink, I used the metal case.

The transformer I used was one of these https://primarywindings.com/product/pwht03a/ but one with a similar rating is fine

[Jez1234]

Nice work there!

[stevehertz]

That is such a brilliant, professional job, and so useful too. Congratulations.

[yampy187]

That looks like a fantastic bit of kit!

[Richardgr]

This is an interesting project, did you end up designing a PCB?

Have you see this thread from DiyAudio, about a device for determining the outer foil of a capacitor. Is that something that could be built in to the tester?

[David G4EBT]

I wouldn't bother with any gizmos to discover which the outer foil end of a capacitor is.

If you've got an amplifier of any sort, all you need to do is to hold the capacitor between your fingers without touching the wires, and applying to ends of the cap to a jack plug at the amplifier input. One way round it will hum (as your body will be picking up 50Hz hum). Reverse the connections, and when the outer foil is connected to ground, it won't hum. Then just mark that end with a Sharpie.

If you cut to the chase in this video, at 2mins 50 secs in, you'll see it demonstrated:

https://www.youtube.com/watch?v=zHuW082TGXg

If you have a scope, you can use that too.

It you hold the cap between your finger, not touching the ends, with the scope tip and ground lead across the capacitor connections, one way rounds the scope will display a flat line, so the outer foil is connected to the ground lead. The other way around, the outer foil will pick up the 50Hz hum from your finger tips.

Pic 1: Displays outer foil to ground - flat line on 'scope.
Pic 2: Outer foil not connected to ground, so the cap is picking up 50Hz hum as displayed on the trace.

(The observant may note that the cap on test did already have its outer foil marked by the manufacturer).

There's nobody more than me who likes making simple little bits of test gear, so long as they have a purpose in mind that can't be achieved by other means. Each to there own, and I certainly wouldn't denigrate or diminish the efforts of those who have designed little outer foil detecting gadgets, of which there are several, and sharing them with others such as ourselves.

Just my take on things.

[GMB]

Where did you get a pot that is rated for such a high voltage?

Don't forget that power ratings of resistors are not usually the limiting factor with very high resistances (check the small-print carefully).

Edit: and also the rotary switch?