C4P restoration(s)

[Steve Gray]

Moving my C4P discussion to a separate topic here.

To summarize:

I recently bought an "as-is" C4P from ebay hoping it might be able to get a working system. Unfortunately it had previously been inhabited by a mouse, causing rusting and other nasty stuff inside. The power cord was chewed up and the case was bent. I had to drill out a screw just to get the bottom off. I managed to clean up the insides and there seems to be less damage than I initially thought. I removed the power cord. The 540B video board seems to look ok with only minor cleaning. Traces seem shiny and intact. Components look good. The 502 CPU board didn't fare so well. Major black stuff had to be removed off the bottom with a brush and soapy water. I can see a bunch of traces that have rusted badly and some are gone, possibly due to my cleaning efforts. The 542 keyboard seems to have come through intact, as did the backplane, fan, jacks, power supply and A15 board.

I have not powered on the machine or tested the cards. This is my 3rd C4P.

1) My first computer I bought new in 1981, upgraded to D&N floppy/memory board and single MPI drive. Was working in 2006 but now doesn't seem to boot.
2) The second purchased from a user group buddy. Has a 527 memory board and second power supply inside the case. I seem to remember it also not booting since purchasing it. Had some mods I didn't recognize.
3) This unit from ebay. Probably used for parts.

I also have a 505 board (without paddle board), two Superboards (not working), and the 610 floppy/mem board.

So, that's about it. It's been a while since I worked on my machines but I really want to get something up and running. I think my first task will be to use machine 1 or 2 and start swapping 502 and 540B boards to see if I can get video.
Usual disclaimer: My time is very limited (which was why I was attempting to purchase a working unit), so I will be doing this a little bit at a time when I can. Of course suggestions are welcome.

Steve

EDIT: I guess I should also mention I have a simple logic probe, a DSO Quad oscilloscope (just learning how to use it), and a 16-line logic analyzer also learning for diagnostics. And, thanks to OSIWEB.ORG I have the schematics and sams info. Wish me luck!

[dave]

Hi Steve,

That sounds like a good plan. If your first computer has good video, that would be a good place to start. Your new tools should be great for the project. Keep us posted with what you find.

Best of luck,

Dave

[nama]

Let us know how everything goes, or post questions if you need any help. I've brought a couple of these machine back from dead and I did find that the connection to the back plane was often an issue. In one case I had to finely sand the pins to get a good connection to the boards.

Phil

[Steve Gray]

Well, I brought out all my OSI boards and such to start working on things. I picked one of my c4P's to be the testbed. I plugged in a 540B board. I tried both of my 502 CPU boards and so far the results are the same. the computer powers on to a 64x32 screen full of random characters. Reset does nothing. Well actually, if I hold the reset down the screen changes but when I release it the same random screen appears again. Tried re-seating chips. Tried checking for overly hot chips but they all seem ok. Only had 5 minutes to work on things, so I didn't do any other troubleshooting.

Will keep you posted...

Steve

[dave]

That's not a bad starting point. Would love to follow your progress on this. Some photos would be super!!

[Steve Gray]

Here's my stash of boards and cases:

SAM_1417-P50.jpg (221.53 KiB) Viewed 10574 times

Below is the machine being worked on:
Steve

PS: still getting the hang of adding pictures to posts (is there a two pic limit)?