Pic of cap, is it a Badcap?

[r-p]

Following from another article on here where I used my powersupply and I got some strange readings, I accidently opened up my SMPS:

Is this cap broken?





It is a 0-30V 0-10A PS and it had a flickering currentlimiting LED at 20V and 4.5A. It has never delivered full power at lower voltages, but 7-8A was never a problem.
The cap, as far as my limited knowledge goes, is not damages: it is just a lacquer type top that appears cracked. I plan on opening it up again eventually, but all my high voltage caps are not available right now (behind several kW of solarpanels that need to be mounted first... I do have a 400uF 350V very old cap that might fit).

[DaveHignett]

Re: Pic of cap, is it a Badcap?

Hi!

Have you tried clipping a lead and testing the cap? I'd try an oscilloscope on the output of your PSU to see whether there's an excessive amount of ripple etc. The cap in question looks like a big old smoothing cap, so if it has passed it's best, then I'd expect a lot of movement in the output of the PSU. On the other hand, you're dealing with relatively high currents, so heat won't be in short supply inside the case of the PSU, so it's inevitable that the laquer will have seen better days really.

Hope this helps!

I'm Dave by the way!

[c_hegge]

Re: Pic of cap, is it a Badcap?

Looks like the rubber seal is ripped. It's hard to tell whether it's leaking or not, though. Is the area around the hole wet?

[r-p]

Re: Pic of cap, is it a Badcap?

Not sure my scope (old one being thrown out at work) works, but that's a good idea.

It could be hardened rubber instead of lacquer.

And it's not leaking anything.

I recently acquired an LCR meter, so I could (and planned) to measure the capacitance, but not sure if a proper reading there would tell you something about its behaviour when needing to deliver full power.

I'll follow up once I get new info. Thanks guys!

[c_hegge]

Re: Pic of cap, is it a Badcap?

If it's not actually leaking then it's probably still OK.

[r-p]

Re: Pic of cap, is it a Badcap?

Follow up: when getting the cap out I couldn't even hook it up to the LCR meter as the lead fell off.

I did not have a proper cap at hand, and parallelled two 100uF 400V caps. It was/is a simple smoothing cap for the 230V input, so the powersupply works perfectly with the smaller capacitance.

I had a better suited cap, but the diameter was too big (it is a very shallow (~5cm/2") powersupply).

Will keep looking for a better replacement, I even have plenty, but they are in powersupplies I might need lateron for projects... For now, it works just fine.

[stj]

Re: Pic of cap, is it a Badcap?

it's bad.

i'v not seen one of those in a very long time, it's an epoxy sealed cap.
they poured epoxy over the rubber bung to stop it leaking so easy.
if the resin is pushed out like that then it's gassed.

your gonna love how much smaller the replacement will be!

[r-p]

Re: Pic of cap, is it a Badcap?

Thanks for the background info!

I'm Dutch = I'm tight

So replacement is probably from my own collection, so likely not much younger

But you're right, in the same volume, I could probably fit 4x150uF 400V caps from a more modern serversupply (the one I didn't want to sacrifice yet for this)...

This forum is not good for me... I don't want to acknowledge that caps age, not with a big load of 75V caps from the early 80's (~400,000uF) and probably close to a Farad in 50V caps from that era...

[r-p]

Re: Pic of cap, is it a Badcap?

Follow up: I replaced the cap with a (probably) Chinese capacitor of pretty much same size and little bigger capacitance and it worked perfectly. (450V 470uF 105ºC iirc instead of the original Sprague 400V 390uF 105ºC cap)

I made a joke about the thing only living for ~25 years before failing on a Dutch electronics forum (the powersupply is from a VERY reputable Dutch powersupply maker, not to be confused with powersupply makers with the same name from other countries. E.g. >90% of schools with technical subjects in the Netherlands will have several of this brand and many will be decades old).

I then got a private message from someone within said company saying I should have contacted them, and I would have received a new capacitor. And that the used/failed capacitor was the absolute best they could get at the time the powersupply was constructed.

Long story short: I received a new capacitor (and placed it instead of the Chinese one) and new adjustment knobs (even though I only asked for the caps of the knobs) for the powersuppy free of charge.

How's that for service... free replacement parts for a device that was well over 20 years old when failing.

[Per Hansson]

Re: Pic of cap, is it a Badcap?

That's pretty cool
Too bad the pics are lost in the first post, if you still have them I can re-upload them...

[r-p]

Re: Pic of cap, is it a Badcap?

Hi. Since I never throw something out... it was easy to find the old cap again.

The blue one is the old cap. The brown one is the replacement sent by the company. But it is build-in, and obviously the text is on the bottom side

The second pic is where the 'laquer' was broken, but no obvious spillage of any kind.