How long does a power supply hold a charge?

[RayB]

I rewired the AC portion of a cocktail that was once Pac Man but had been converted to JAMMA... I Followed Bob Roberts' AC wiring map to the T. I have tested it without the monitor power, no circuit board, no controls, and no lighting hooked up.

AC reads good. Power supply reads OK (5.2v, which I'll adjust later).

Here's what my question relates to: I turned the power off, and still got readings off the power supply for a short while. (like 5 or 6 seconds later, maybe longer). It made me think I had wired the AC wrong and maybe the "hot" side wasn't getting switched off. But then I'd measure the AC input at the power supply and get zero. I'd measure the 5V and 12v again, and get something like 0.02.

I checked the AC and measured AC from different points with the switch and interlock OFF and I get no readings. Am I worried for nothing?

[shardian]

Yeah, I think you are.

Ever notice that some electronics with led's will have the led lit for a few seconds after power is disconnected, then it will fade out? That is residual capacitance charge still powering the led. Some items have a longer bleed time than others.

[SirPeale]

Yep!  I agree with Shardian.  It's the caps bleeding off their voltage.  Ever crack one open?  They're pretty beefy.

[Mauzy]

Ever throw a recently (like 30 seconds before) tested "dead" power supply in a junk box? Heard a pretty loud crack, turned around and it was sitting solder side down on a big piece of metal. All those caps really added up!

[RayB]

Cool!