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Floppies_only
April 26th, 2008, 10:02 AM
Gang,

I've heard that the CIA chip (Complex Interface Adaptor) in the Commodore 64 is connected to the joystick ports (Control Port 1 and 2) and that it is susceptable to damage from static discharge. You shouldn't touch the pins of the control ports because doing so can send a shock through the CIA chip and damage it.

I knew this but it was hard to remember and when I unpacked my new C64 I did it anyway. It occurred to me that it might be possible to protect the C64 from this touching. Take an IBM PC serial mouse or a non-functional Commodore mouse or joystick. Cut the cord far enough from the connector so that you can attach the end of the cord to the backside of the C64 - the side that is closest to the monitor. Then spiral wrap electrical tape over the end of the cord. Electrical tape is designed to stick when it is streched over the item you are taping. Finally, tape the end of the cord to the backside of the C64.

This is not guaranteed to work. In fact, I don't know that it will work. But if it is hard to remember not to touch the control ports on your C64, this measure might protect your CIA chip from static discharge.

Sean

Soupwizard
April 26th, 2008, 10:19 AM
When I was in college an engineer friend who also had a c64 told me about this, and his solution was to take some of anti-static foam that ICs shipped stuck into, cut a piece to fit the joystick port, and stuff it into the port. Said it would drain the large spark from your fingers off to ground, but still allow the ports to work normally.

tezza
April 26th, 2008, 10:36 AM
I blew up a CIA chip in one of my c-64s by accidently touching the port. It is SO easy to do, as the port is right next to the on/off switch.

I would go as far as saying it's a design flaw!

Tez

Floppies_only
April 26th, 2008, 12:26 PM
When I was in college an engineer friend who also had a c64 told me about this, and his solution was to take some of anti-static foam that ICs shipped stuck into, cut a piece to fit the joystick port, and stuff it into the port. Said it would drain the large spark from your fingers off to ground, but still allow the ports to work normally.

Did you try it? What results did you get?

Sean

Soupwizard
April 26th, 2008, 12:46 PM
Did you try it? What results did you get?

Sean

It seems to work well - joysticks still worked, and I never lost a CIA chip (after the first one, which is when my friend told me about the trick)

carlsson
May 10th, 2008, 01:20 PM
Regarding CIA chips, today I picked up two broken C64 motherboards. Neither did power up, and one was missing the 6526 chips. Therefore I moved them from one board to the other, without success. I tried to power on the first board without chips, and got the regular startup picture, all fine except no cursor etc. It appears one or both CIA chips are broken (short circuit?) to the point the computer doesn't power up. I'm unsure if even Ray Carlsen has this symptom in his list of diagnosing faults. Now I only need two good CIA chips, and I'll have another working C64 breadbox.

evildragon
May 10th, 2008, 02:19 PM
Ray Carlsen, that name rings a bell.

I believe I had emailed him a while ago, when my glu chip in my C64 died, got advice, took the advice and purchased a glu chip and replaced it, and ended up fixing my C64.

carlsson
May 10th, 2008, 04:32 PM
Yep, he is well-known in Commodore circles and actively repairs stuff as well as posting on his web site how to do it.

As I thought, in his list of symptoms it says a bad CIA should still make the computer boot normally. I guess I should mail him about my discovery.

http://personalpages.tds.net/~rcarlsen/cbm/c64-ic.txt

Edit: Oh well, it says so in the accompanying document:


A shorted CIA can produce a blank screen. You will get a startup screen with the CIA's removed but you will have no cursor without U1 (keyboard interface) plugged in.
http://personalpages.tds.net/~rcarlsen/cbm/c64blank.txt

Floppies_only
May 10th, 2008, 05:25 PM
Regarding CIA chips, today I picked up two broken C64 motherboards. Neither did power up, and one was missing the 6526 chips. Therefore I moved them from one board to the other, without success. I tried to power on the first board without chips, and got the regular startup picture, all fine except no cursor etc. It appears one or both CIA chips are broken (short circuit?) to the point the computer doesn't power up. I'm unsure if even Ray Carlsen has this symptom in his list of diagnosing faults. Now I only need two good CIA chips, and I'll have another working C64 breadbox.

I think that this is a good time to tell people about http://www.oldsoftware.com/

I've ordered from them twice and both times they sent the order the same day and I got it the next day. Items were as described and worked well for me. They offered tech support on the stuff that I bought and they told me what to buy after I told them what I wanted to do.

I believe that you could buy some mother boards with CIA chips on them to repair your C64. Shipping might be expensive, since they would be comming from the USA, perhaps you'd want to buy a "for parts" C64 off of eBay Sweden instead.

Sean

carlsson
May 11th, 2008, 02:26 PM
Well, I have a local friend who probably has a stash to part with, or else I could find chips locally for little or no money. In worst case, I have contacts with collectors all over the world who usually send common chips for postage costs.

By the way, there is no such thing as eBay Sweden. It is called Tradera and is a separate auction site, although owned by eBay. A few years ago, eBay did a half-hearted attempt to open their own site in Swedish, but failed miserably so they had to buy the biggest competitor instead. But that is another story.

Arkhan
June 24th, 2008, 12:09 AM
They make these neato little covers for the joystick ports to protect them, and I cant seem to find the link to them right now. Theyre pretty useful though