Are my C64 power supplies ok?

satanshollow · Posted: Sat Aug 11, 2012 4:55 pm Post subject: Are my C64 power supplies ok?

I have 2 of them and just measured the voltages.

1 is 5.19 DC and 9.9 AC

2 is 4.97 DC and 10.2 AC

They were measured with out being connected to a computer. I want to make sure they are within tolerance before selling them. The last time I checked years ago they were ok. Thanks for any help.

davidcallan · Posted: Sun Aug 12, 2012 5:36 am Post subject: Re: Are my C64 power supplies ok?

They read OK, although 2 is a little low (and I'd be suss on it for that) on the DC side. (you get about a 0.2V drop between the PSU and the C64 power connector on the 5V line, under load - with no load, you're getting the voltage directly at the PSU.)
10.2V AC is a little high, but I wouldn't be too worried - no chip gets that directly - it's regulated first. It IS the unloaded voltage (and will drop noticeably under any load), and there's nothing you can do about it anyway, it's just what the transformer outputs - Unlike the DC output, it's not likely to suddenly spike to damaging levels.

One of the problems I've observed with C64 PSU's is that they go overvoltage when HOT.. something you really can't test. (aside from one of mine that actually caught fire!!!)

Just sell them "as is" - and with the blanket caution that any old electronic equipment can fail - particularly underengineered, 25+ year old electronic equipment Very Happy

Callan

Catboy · Groupie Joined: 19 Mar 2009 Posts: 261 Location: Germany

Here's a tip:

When testing a PSU, connect a few 6V-bulbs parallel to the +5V output so they draw about 800mA. They will act as a convenient load.

Let the setup run for let's say half an hour and re-check voltages while the lamps are still connected. As long as the 5V don't read too low or shoot up to over 5,5V the power supply seems to be okay.

-Catboy