C64 overhaul help (Page 1 of 2)

Try to match the originals as closely as possible, there is a big difference between electrolytic (usually cylinders) and ceramic caps.
When changing electrolytic ones, the negative lead is clearly labeled on the package - you absolutely need to preserve the same polarity - otherwise the cap will go "poof" in a few seconds.

IIRC the SID itself actually uses some special capacitors for the filter part - someone else please clarify this!

PLAs tend to overheat, so a heatsink on that is definitely a good idea. I'd put the heatsinks on first, chances are the ICs didn't really fail at all, given you were still able to power the machine on. Seems like you might be right with either the power supply or the C64 counterpart.

You mean the external one? From what you've written, it actually looks like the culprit to me, so I'd look into that. Better would be to just borrow one from a friend first, but since it's not really the '80s anymore, that of course depends on if you have friends with C64s :].

Also it might be a good idea to google for some C64 technical / repair manuals, those usually have a table with symptoms, possible causes and things to check / replace.

tl;dr: I'd go: service manual first, then try a different power supply, then heatsinks on ICs, if all that fails, recap / replace ICs / replace machine

Good luck, hope your C64 is gonna be ok! :]

No problem!
Cool, didn't know about this site. The note about voltages reminds me though - the rated voltage must be the same or bigger. Don't replace with smaller values, unless you're sure. They probably only warn you because they send some with bigger voltage rating (and that is OK).

If you by any chance run into a situation where the original caps are rated higher, it's better to double check with the schematic or ask someone to check for you. Generally, most of the C64's internals run on 5 V or 12 V, but the internal power circuit could require bigger values.

Hopefully your power supply didn't crap your system. They are "suicide" power supplies. They didn't have any built in protection in them for when they go bad.

I'm gonna assume you have this model: https://www.amazon.com/Craftsman-11-fun … B00GUJK7GW

1. Open this: https://www.c64-wiki.com/index.php/Powe … _Connector.
2. Set the meter to "VDC"
3. Put the black cable in "COM" and the red one in the connector that has "V Ω CAP Temp Hz μA mA".
4. Plug the PSU in the wall outlet
5. Look at the picture in step 1, connect the black test lead to pin 2 (bottom, GND) and the red to pin 5 (you can also try 4, but there might not be anything depending on the PSU model). This should read a voltage somewhere around 5 V (some small difference is OK).
Be careful to only touch the specified pins and even more so to not short anything with the test leads (don't even touch the metal outer ring)! This can be tricky - fixing the PSU connector in place is recommended, also maybe rest your hands against something if they're not steady.
6. Remove the test leads and switch the multimeter to "VAC"
7. Once again put the black lead to pin 2 and measure pins 6 and then 7 with the red one, they should both be at about 9 V.

That should about do it.

(For a bit of a background: The meter (in VDC / VAC modes) measures the voltage difference across the COM and the right socket. COM means a common wire (that has the same voltage in a system) - it's usually used for ground and that means you'd expect 0 V on it. Black color is commonly used to mark that. Then the red lead is used to compare any voltage in the system against the reference/ground/common voltage.)

You've been very didactic Kvee, that's kind of you. I did the same for my PSU, except I wasn't careful enough and I shortcut two pins, which burned the fuse... I suggest you use a plastic cylinder around the pins (from a ball pen maybe?), that could help to isolate the outer ring and other pins.

Maybe I can ask a general c64 PSU question: what's considered acceptable for the AC voltage? Seems like I've seen ~12v, is that a problem?

Ok, so, I tested out my power supply (supplies, as it turns out) as instructed. Here they are:

One of these came from a VIC-20 I purchased a while back. I'm honestly unsure of which is which. I mixed them up during testing a few months ago. Is there a serious difference between them? Anyway, both of them put off 5v on pin 4/5 fine. I could not get pins 6/7 to read 9v. It always hovered around 4-5v. Initially spiking at 7v. It also seemed like it was either pin 6 or 7 putting out power rather than BOTH. This happened on both power supplies. Do I have my multimeter on the wrong setting?

Could both supplies be malfunctioning? Which one should I be using with my c64?

In relation to one of my earlier question about chips, here's my pcb:

ASSY NO.250407 REV.A

I've heard that "fried" chips get a glossy sheen on the top of them rather than the matte finish they usually have. It seems like the two chips in the upper left have a different texture than the rest. Are they fried? I did notice some funny performance when loading up Turrican. Sometimes the whole system would slow down when certain effects were used on the title screen. Maybe it was just a bad crack of the game but it seemed almost as if strange characters were showing up instead of the proper effects.

Thanks again for your help!

Last edited by gilhelm (Aug 11, 2016 1:50 pm)