800xl Cannible-ize Help

[Paul Westphal]

I have 2 non working 800xl mainboards. The light comes on but no-one is home on one of them. The other has a solid white bar on the right. I was going to start swapping chips to see if I can get one to work. Any Ideas on which ones more commonly go out? Where should I start? I would hate to scrap them.

[+David_P]

Do you have a known working 800xl? If so, use it to determine which chips are working from the two malfunctioning systems.

[Paul Westphal]

That's a lot of swapping, but a start nonethless. Thanks. I will start with the 6502 and work my way down Can I power up the board without a case?

[russg]

That's a lot of swapping, but a start nonethless. Thanks. I will start with the 6502 and work my way down Can I power up the board without a case?

yes. Be careful not to set it on a conductor. Would short.

[Rybags]

You can power up without a case no probs, no keyboard needed either but having one attached can be of help if it's only partially malfunctioning. Just ensure nothing can cause shorts - an old shoebox can be ideal for resting motherboards on.

Of course though, running a keyboard outside the case might cause potential for shorts in itself so take care there.

 

As was said, swapping one chip at a time into a known good system can make it a whole bunch easier.

 

Stuff I'd be testing in order - CPU, Antic, MMU, OS ROM, RAM, PIA. Generally if the CPU is bad or otherwise unable to run the initial OS powerup stuff the screen will have a dark brown or reddish colour.

 

Sometimes having a game that runs in diag cart mode can help too. Star Raiders and Asteroids are 2 such games, also they only use the bottom 8K RAM although since XL/XEs have Ram such that the 64K systems have chips that contribute 1 or 4 bits of data to every possible address, a failing chip will often affect everything.

Edited December 16, 2013 by Rybags