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Just picked up an SX-64 for $20

Doesn't sound too good. Have you tried hooking up the system to an external monitor and/or blindly typing load "$",8 as was suggested previously? Just wondering if you have more issues than just the monitor.
 
It could be that the screen control is set too high. These are usually mounted to the flyback. Use an insulated screwdriver to adjust.
 
Neither sounds nor loading have worked. I suppose I have a system board issue. I'll try resetting the chips, but what if that doesn't work? Would other components on the board go bad?
 
Well, to separate out the two problems (monitor vs. cpu board), you can always use the external video connection from the SX-64 to an external composite monitor or TV.

All the regular C-64 chip problems can occur with the SX-64. Practically all of the socketed chips are interchangeable with the standalone C-64's chipset. Back in the day I had some faulty RAM in my main C-64, so that is not out of the question also. SX-64s are rare enough that I think it's a worthwhile endeavor to attempt a repair.

Are you sure all the power supplies to the main board are correct?

Back to the monitor issue... see if you can adjust the screen control as I suggested and see if that darkens the screen any.
 
What is the word on SX-64 PLA's? Those little gremlins usually are the cause for all breadbox C64's to stop working at all. Supposedly though the PLA in the C64C and upwards is said to be many times more reliable. Other candidates would be to remove the SID chip - 6581 in your machine - since a broken SID can halt the computer but if it is missing, only the sound and paddle (?) functions will be missing. You should also look at the two 6526's, same chip but serving different means. If you are able to swap those, see if you get any other output on the built-in or preferrably an external monitor. Since you mention the screen is all white, that equals the value in 53281 on start-up. You should get a white screen with cyan border on the SX-64. I would have thought you would get a cyan screen if the display won't open or initialize properly, but the white can have other causes.
 
Power to system board is OK.

Removed SID--no effect.

Reseated all system chips--no effect.

Didn't see any controls on the flyback itself, but there are two set above it marked "JVC" and "Focus." Turning either changed the color of the screen slightly, but had no other effect.

Swapped 6526s, and I still have a white display, but now the floppy light doesn't come on and the drive runs constantly.

PLA?

What type of connector does the external video require?
 
Tiberian Fiend said:
I can do you one better.
Click to expand...

It's the one smack dab in the middle of that picture.

Surprisingly, this company shows quite a few in stock in three distributors. :)

http://www.hobid.com/electronic-component/906114-01/

I'm not sure if these are swappable from a regular C-64 or not. I think they may be if you have access to one. It's certainly the best place to start with a diagnostic. Interesting that your results from swapping the CIAs around were what they were. I'd try and get my hands on a donor C-64 and try swapping the PLA and the VIC-II and/or CIAs from that as a good first step.
 
Alternatively, I could buy one from eBay. Ah, eBay... the place where a single pulled chip costs more than buying and shipping an entire machine.

I actually do technically own a C64 breadbox. It's a long story, but I doubt I'll get it back from wherever it is.

I think I'm going to hit the old CL and see what turns up.
 
Sounds like the long story behind how I lost 90% of my Commodore equipment. I think I lost three complete systems (64, 1541, 1702) to a former friend. I'll never see them again. At least I still have my 1571 and 1581 though. Those would be a lot harder and costlier to replace.

CL is probably your best bet. Post a wanted ad if there aren't any out there. Most likely it'll only take a few days for someone to contact you. Lots of people still have them in basements and have no idea anyone would be interested in one. And frequently, where there's a 64, there's other interesting stuff.
 
Well, no. Back 1996ish (I would've been about 12), I took $50 I got as gift money and went to a computer repair shop with my cousins (twins) to buy a computer, where the only one the proprietor offered was a 286 wiped clean with no monitor. Since it had no monitor, my cousins duped me into trading the 286 for their Commodore 64, which could use a TV as a monitor. It had little software, and I had no way of getting more, so I ended up just giving it back to them (I didn't have the space to store it). Today, one cousin lives in Phoenix, and the other lives in Italy. There's no telling where the C64 is now. They probably traded it away again long ago.
 
Not that it normally is the culprit but was there ever a sticker covering the window on the EPROM or did you find the sticker for the EPROM sitting someplace inside the case?
I ahve seen all sorts of weird things happen if the window was left exposed.
 
Yes, anything that blocks sunlight. However I have been able to read unprotected EPROMs that have been inside a computer for 20-25 years. As long as no sunlight reaches the chip, I think a missing sticker is not a disaster although not preferrable neither.
 
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