Hi,

I've recently come into possession of two C64s(one C64, and one C64C). The power supply is missing a fuse and the holder for it, so I'm looking to find/build a replacement supply.
I have a power brick that provides both 5v and 12v DC, and since 9v RMS is around 12.6v DC, I was thinking that if nothing in the C64 actually requires AC(as opposed to the ~12v DC that can be derived from it), that I could use that. I've heard that the 9v AC is used to obtain 12v DC for the SID.
So, does anyone know if there is anything in the C64 that requires AC, or if I can safely(without killing the C64) substitute 12v DC?

It’s not that easy, afaik the 9V AC is used:

on all board revisions by the TOD (time of day) clock and is passed through for USERPORT devices.

on the older boards:
ASSY-NO.250407
ASSY-NO.250425
ASSY-NO.250466
for a second 5V DC line (CAN) and for the 12V DC for the SID and VIC-II.


on the newer, cost reduced HMOS boards:
ASSY-NO.250469
for the 9V DC for the SID.

The best way to be sure is to look at the specific schematics for your board revision at zimmers.
http://www.zimmers.net/anonftp/pub/cbm/ ... index.html
http://www.zimmers.net/cbmpics/c64s.html

However, I wouldn’t go to the trouble and use modern 5V DC – 2A and a 9V AC – 1A wall adapter and connect them to the old power supply cable.

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Marco

As Marco noted, 9 VAC is used to drive the TOD clocks in the two 6526 CIAs, so you do have to provide it to the C-64. I think that you can find the original power supply's schematic somewhere on line. It's not a hard thing to replicate.

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

Does the C64 run reasonably well, or not at all, without the time of day clocks?

That I don't know, although I do know the "kernal" makes no reference to either clock. I vaguely recall that the 9 VAC was used for something else as well, but it's been too long since I looked at the schematic to say for sure what it was.

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

Thanks, everyone. I'll probably try to replicate the power brick, as I don't really want to have to use two power supplies to run one thing.
If I thought I could get the case on mine open I'd try gutting it and using the transformer in that. I may end up using two supplies, because I'm not certain that whatever I do with the mains power will be safe.

The Datasette port requires 9VAC for the K7 motor.

Sans that, a C64 will run just fine without the AC.

You can gut and repair the existing brick, it's been done. Please add a fuse if you do, and be careful about re-potting. The potting may have had heat conductivity or it may not. If it did, you'll need some way to remove heat. But re-potting is not really desirable.

You probably already know, but as a general warning, no potted C64 brick is safe to use unless it's already been rebuilt. The regulator always fails, eventually. And it fails in an overvoltage state.

How would I get into the thing, though? There aren't any screws visible on it, and I don't really want to smash it open. If it helps, the model number is: 251052-08, and it's a black wedge-shaped one. And then I'm not sure how I'd deal with the potting. I'm never going to re-pot the thing, though, that's probably why they fail.

If I don't rebuild the power brick, what I will probably do is make a small cable that would accept the power plug, and take only the AC from the original supply, and the 5v DC from a 2A USB wall wart, and then feed into the C64, as I can buy the connectors.

I've never seen a wedge shaped one, I don't think.

Normally, you can cut them open with a knife, or cutoff wheel.

Hacksaw!

Look for where the seam is, and make a shallow cut around all four sides. Be sure to keep the blade parallel to the side you're cutting so you never accidentally cut deeper than necessary. If it's done neatly you might be able to put it all back together afterward without it looking too terrible. (OTOH you can end up destroying the thing if your luck and/or skill fail you.)

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In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html

A jewellers saw might be even better, provided you can get a long enough blade. But a hacksaw wouldn't be terrible.

Sorry to bring up an older post.

But it's no secret that the C64 power supply is the cause of many destroyed chips in the C64. In fact, recently, the "8-bit Guy" destroyed some chips on his C64 as he was filming a video about some C64 peripherals.

From what I understand, the faulty PSU sends way too much voltage/current and many of the chips burn up.

There are a few solutions to this if you aren't going to build your own PSU. One is the custom built PSU's from Carlsen (just Google Carlsen C64 power supplies). They are a little pricey but many people on the Lemon forums recommend him.

I chose a different (cheaper) route and that was to buy a "SaV64" kit from someone on the Lemon 64 forums.

http://www.lemon64.com/forum/viewtopic. ... 9&start=60

Her name is "SkydivinGirl".

The kit she sells (she also sells them assembled) is basically (from what I understand) an over-voltage protection circuit in a really nice enclosure. The device allows you to plug in your legacy C64 power supply and if it draws too much it will shut it down. The neat thing is that it also allows you to plug in modern "wall wart" type power supplies too. So, you can choose to allow the C64 PSU to provide AC only (which seems to be stable) and you use a modern DC PSU. Or, you can use a new AC and a new DC PSU through it. Granted, that would be TWO PSU's going into this device but it's a small price to pay for added safety.

_________________
Cat; the other white meat.

I ended up going the route of dual plugpacks. It turns out that the fuse holder went missing at some point, and I didn't feel like trying to make a replacement.
The 64s themselves have issues, too. The 64C has a dodgy power switch, and the 64 does things I didn't tell it to when I press too hard near the 'A' key.
On top of which, the small composite display I was using did not do me any favours for readability. I would be trying to enter MLX(A type-in machine language entry program), and it would run what I'd entered. I ended up saving to tape after each line(and they were usually long lines). I stopped using them after I started on Uni(I didn't have the time. This tri is/was hectic).