7

My original (1983?) Commodore 64 (brown breadbox with grey function keys) has trouble powering on. Specifically, when I flip the power switch the power LED will glow dimly and the machine fails to display video. However, if I unplug and re-plug the physical power (DIN) connector (with the power switch in the on position) the computer comes right up and the LED glows at full intensity.

I know C-64 power supplies are notoriously bad, but if the power supply were the problem I'm not sure the unplug/re-plug trick would work so reliably - so I was thinking maybe the switch is janky. I'm going to try swapping the power supply for a home-brew rig I keep in storage (that I know is reliable) to see if that impacts the problem, but in the mean time:

Is there any known history regarding the C64 power switch failing on early (read: before 1985ish) models? Also, if anyone has any good suggestions I wouldn't object.

Improve this question
4
  • 6
    I've repaired a number of faulty C64s and never seen the power switch itself go bad. Usually it's either the (if original) power supply itself which are notoriously unreliable after all this time, or the solder joints on the DIN connector or power switch that go bad. Have you checked all of those? You should be able to visually see the bad solder joints, and can measure the power supply voltage with a multimetre when the LED is dim.
    – Dawn Minion
    Commented May 28, 2019 at 12:35
  • 4
    I have recently discovered that the female connectors in the DIN socket can break at the joint where they come out of the back of the housing and fold down towards the PCB; a small tuning fork-shaped bit of metal drops out. Thankfully for me it was one of the unused pins in the A/V connector. Maybe there's some fatigue there? Unplugging and re-plugging would certainly be agitating things in that area.
    – bodgit
    Commented May 28, 2019 at 13:16
  • 1
    Single data point for my pre-85 C64: the PCB connections of the power switch had dry joints and work reliably when resoldered.
    – scruss
    Commented May 29, 2019 at 12:29
  • I worked at a shop that handled a lot of C64s in the mid-eighties. Usually the bad power supplies were bad out of the box. If it's still working after all these years, it's likely the solder joints from plugging it in many times.
    – Cliff Hall
    Commented Jun 30, 2019 at 23:35

2 Answers 2

Reset to default
3

A history of failing is maybe a strong statement, but for what it's worth, I've seen a couple of failure modes of the power switch during C64 repairs.

The most typical is that solder joints become loose due to the mechanical stress on the button, which can lead to no or poor connection, similar to what you describe. This can normally be fixed by resoldering the joints.

I've also seen a failure mode where environmental conditions (presumably) had caused contact surfaces to degrade and not conduct properly. This could be fixed by repeatedly bathing the switch in contact cleaner and exercising it.

Finally, I've seen one that had a mechanical failure in it so that it could not turn on. Replacement was necessary.

I don't really have any numbers on how often these failures occur (and assume they are also a function of external factors), but I'd say that in my experience it's not uncommon.

Improve this answer
1

I also am resurrecting my C64 and have experienced the same problem after the power supply has been up at least 30 minutes. The power led is powered by the 5 volt DC supply from the power brick, not the 9 VAC side of the power brick. I opened the C64 case and using a voltmeter measured 5 volts DC on half of the switch contacts. Flipping the switch on, the 5 volts DC dropped to 2 volts (power led on weakly). If I carefully turn the switch towards off, but not off and return to the on position the 5 volts is present on the switch contacts and the system boots up. For my C64, the problem is not the switch or contacts or poor solder joints, but the power supply itself.

On my C64 the 5 volts DC at the switch was 5.21 volts with the unit booted up. From reading other articles the voltage is too high and an indicator the power supply is failing. Am replacing it. Good luck

Improve this answer

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .