<- Needs Help With C64!

[vb_master]

I need some help fixing my C64. It was powering on for a while, then it won't do it. Once in a while, the LED will light up, but that's it, and it won't show the BASIC screen. Once in a while, a white screen will show up, with no LED. I know the adapter is working, and the whole unit was working because I was working in BASIC, but when I flipped the switch from off to on with the power, it didn't work, yet if I had the switch to on, and plugged in the power, it would work! Can some one help? I think it's the switch...

[Artlover]

Well, I know on the C-128's the switched failed sometimes. Mine failed more then once. So I see it happening on the C-64 too, since it's the same.

 

Problem is trying to find a replacement that just drops in without any modding. Never saw anything in Digikey, Mouser, MPJA, Jameco, Alltronics, Unicorn, etc.. On my C-128, the first time I took the switch apart and fixed it, which lasted a year. Second time I took the switch out of an old C-64 to use as a replacement.

 

C-64's also have issues with the power socket wearing out and not making full connection across all 4 pins. That happened to me on my old C-64. Again, finding a replacement becomes problematic.

 

It's why I've got like 5 or 6 spare C-64 mainboards, and a couple of C-128 mainboards, and a bunch of loose chips/switches/sockets from trashed mainboards, in addition to my working units. So I can "keep" them working. (I'm sure you Atari 800 guys are the same?)

[vb_master]

So can I have a switch?

 

EDIT: Ran the system for a while, and the RAM chips were really, really hot! This means that they are shorted, right? But that doesn't explain the LED problem...

Edited November 6, 2005 by vb_master

[Artlover]

So can I have a switch/power socket (which I bet is the problem)?

961146[/snapback]

If I had them handy, I'd be glad too. Unfortunatly, as it stands, all my old gear is "somewere" in my 10x10 storage unit that is packed wall to wall/floor to roof. You're welcome to come here to OKC and try and find it. Shouldn't take more then all day. Let me know if you find my other video camera, I need it.

 

Do your local thrift stores ever have 'em? I've picked up C64's for $1.99 before. Cheaper then any single part is worth.

 

Of course if you don't care what it looks like, improvise. I know, I'm speaking pure evil here; the deflowering of vintage hardware with work arounds and hacks. (/action beats himself with a old non-burst mode compatable serial cable.) Doesn't have to be permenent tho, just till you can get the propper parts.

 

If I come across them I'll pull a switch & socket out for ya, but I honestly have no idea when that might happen. So you might want to keep an eye open in the thrift scene. Hopefully someone else here has a more readily accessable source of parts.

 

I mostly replied just to let you know it's a somewhat common problem, and that you're on the right track in thinking thats what it is. Nothing worse then spending time and effort on a problem only to discover that wasn't the problem at all. Been there, done that, broke things into 100's of little pieces because of it.

[Artlover]

EDIT: Ran the system for a while, and the RAM chips were really, really hot! This means that they are shorted, right? But that doesn't explain the LED problem...

961146[/snapback]

 

When the system was running, was it working ok. Could you type in a little proggy and have it run ok? If so, I wouldn't expect anything to be shorted.

 

Now, the thing about the Commodore's is their use of both DC & AC current. AC is used by the system for a few things like clock & sync. System getting out of sync I can see generating extra heat.

 

If I remember, a C-64 will power up and sorta work for a short time without the AC leads, but will be prone to crashing, especialy on anything using the SID chip. (128 doesn't come up at all).

 

So this leads back to possible power socket issues. Possibly even power supply issues. I don't remember if the LED is powered off the DC side or off the rectified AC side. Been years since I touched anything CBM.

[vb_master]

The problem is that there is no video, yet there is an LED... I have no idea what happned. I went out today and got a new switch, I'll see if that helps.

[Flack]

I don't know much about fixing 64's, but I have several in my garage and the last two I bought cost less than $3. You might check your local thrifts for a an old Commie to use as a replacement or for parts.

[supercat]

Now, the thing about the Commodore's is their use of both DC & AC current. AC is used by the system for a few things like clock & sync. System getting out of sync I can see generating extra heat.

961187[/snapback]

 

The system feeds the 60Hz from the AC line to the CIA chips for timekeeping purposes, but doesn't synchronize anything else with it. On the other hand, the AC voltage is used to generate a +9V or +12V supply (depending upon revision) that feeds things like the SID chip. I don't know why the SID chip doesn't just use +5, but my guess would be that using a higher voltage makes it easier to use FETs as open-loop amplifiers in their linear region. Anyone know?

[vb_master]

I just installed the new switch. No LED, just flashes a white screen sometimes. Should I just trash it?

[supercat]

I just installed the new switch. No LED, just flashes a white screen sometimes. Should I just trash it?

961903[/snapback]

 

Depending upon vintage, you may find someone willing to pay shipping in order to use it for parts. Except that the guy I lent it to never returned it, I had a moderately-early ($300 era) Commodore 64 and all the major chips were socketed, but some were a little 'iffy'. Had been since I got it (perhaps shoulda returned it but I didn't); since then I'd replaced the VIC and one of the CIA's.

 

BTW, I wonder if anyone else has seen the problems I saw: (1) two of the sprites (#1 and #7 I think) would be missing about the leftmost 1.1 pixels from any "run" of pixels. In single-width mode, a single pixel by itself would not show up at all. (2) The "real time clock" on the keyboard CIA wouldn't carry from seconds to minutes. This made Raid Over Moscow much easier; (3) pressing "A" and ";" simultaneously would cause continuous interrupts from that CIA, and would also reset the "real-time clock".

 

Anyone ever seen a C64 like that? I don't have those old chips any more. Too bad. Otherwise I could sell 'em on Ebay as a "special possessed edition".

[icbrkr]

A dying power supply can also give you really odd results - when mine was dying it would power up.. eventually. I'd have to leave the power supply on for about 30 mins before it kicked in.

 

If you have a breadbox C64, a lot of us could really use the chips in it before you throw it away! I need another SID for my C-one.