Power supply (capacitor) works after months

On Thursday, December 5, 2019 at 5:11:08 AM UTC-5,

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Old timers used to (allegedly) *fix* bad electrolytics by tapping them with the back end of a wrench. These were the metal chassis mount varieties, a nd banging them would compress what was left of the electrolyte inside. Sq ueezing with pliers was another option. Be aware that I heard of this as a lad back in the 1960s, so this would have been on older types caps, not wh at we see today.

Compressing those old style metal can caps might have bought some time but I think squeezing modern paper electros would do no good at all. When I ge t to work, I'm going to try that on some bad caps and see if there's any im provement in value and ESR.

Getting back to your problem, I think gramps is right; it's probably a tire d electro (that would be "swell"). These almost invariably work far better when heated, so if the brick was sitting in a warm area, it might spring t o life. Alternatively, you can heat the brick with a hair dryer or heat gun to get it to work, but these are only temporary solutions. Crack the bric ks open and change the electros with the bulged tops. That will get most r unning. If not, you'll have to either ESR or replace the rest of the caps. Lower value caps on the primary side of the SMPS bricks generally go weak but don't swell or bulge.

are only temporary solutions. Crack the bricks open and change the electros with the bulged tops. That will get most running. If not, you'll have to either ESR or replace the rest of the caps. Lower value caps on the primary side of the SMPS bricks generally go weak but don't swell or bulge.

I agree, many of the capacitors made for switching supplies seem to go bad. Often the tops will bulge out. Sometimes heating them will make the supply work but if you turn it off you have to heat them again.

I have replaced capacitors in several pieces of gear and that seemed to be all that was wrong with them. I had one piece of test equimpment I bought surplus. It was made around 1995 and cost about $ 50,000 back then . It was to test the older cell phones. Bought it a few years ago and sometimes it would take about 2 to 5 minuits to come on. It should start within a few seconds. Replaced about 5 capacitors in the power supply and now it starts up in a few seconds like it is suppose to.

There is physics behind with just letting it sit. CMOS logic chips can semi

-permanently change state with a surge. Waiting, "along time", can fix it. I've used an accelerated method multiple times to fix stuff. Bike comput er (dragged over nylon rug), car clock (stopped after car was jumped), HPca lculator (displaying commas for decimal points)

Thanks to all.

I let it run 24hrs, then shut it off for a few min and turned it back on, seems fine. The lesson for the last time seemed to avoid prolonged non use.

Aside:

A few years a had a supercapacitor watch. Spozably charged by moving. I loved it. Then I got sick for over a week and the watch got uncharged and never worked again. Bummer.

- = - Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus blog: panix.com/~vjp2/ruminatn.htm - = - web: panix.com/~vjp2/vasos.htm facebook.com/vasjpan2 - linkedin.com/in/vasjpan02 - biostrategist.com ---{Nothing herein constitutes advice. Everything fully disclaimed.}---

There is usually a cap in the startup circuit that can cause that. It will be on the hot side. Sometimes you got a resistor to the raw B+ which hits a source from a tertiary winding that powers the drive circuitry. Caps on th e secondary side don't generally cause that, and even if they get slightly weak there are more caps on the mobo to take up the slack. If they get real ly bad and the ones on the board are not enough you might get erratic opera tion and maybe even data corruption. Even when it is not that bad those cap s being bad can cause it to be more susceptible to momentary power glitches one of which just destroyed the OS in one of my boxes. I'm going to reload it one of these days but haven't gotten around to it. Lazy, and when I get unlazy I got work to do. In that one if the caps were in better shape they would have held a charge long enough, there were three outs of duration in milliseconds. It shouldn't have affected anything.

Be aware that that is exactly the symptom you get with an older, dying elec trolytic. Shutting off a few minutes will not be long enough for the warme d up capacitor to cool it's core, particularly if it's a brick supply that isn't generally well ventilated.

I'm not saying a lazy cap is your problem, but it's a high probability from your description of symptoms.