XEGS Repair

[hawk]

I finally got a round 'toit' and started having a go at repairing a non-working XEGS that I bought a few years ago. The two RAM chips were running very hot, so I've started by removing them. While I'm waiting for the new IC sockets to arrive so I can continue the repair, I thought I'd ask what to expect if I turn the machine on without any RAM?

 

Aside from the RAM chips running hot, the other symptom I have is a black screen, and this got me wondering whether the RAM test would run at all if the RAM wasn't installed, and that I've actually got another fault as well that will need new another new chip.

 

Any ideas?

 

Thanks,

Hawk.

 

[mr-atari]

No RAM will give black screen, nothing further.

The memory tests does need some good ram cells to run.

So without nothing happens.

 

Bad rams in XEGS is a very common issue, running extremely hot.

Just replace and you are fine.

[Rybags]

Usually you'll have a brief red/brown screen when powering up the later A8 machines.

 

If the screen stays that colour it's an indication of something wrong other than Ram - might be a dud CPU, bad MMU or OS Rom.

No machine will do much without any Ram present or if the Ram is extremely faulty, though the described colour change should still occur in most cases.

 

In theory a diag mode cartridge could perform some rudimentary system validation tests without Ram - not sure if the SALT carts do any such thing but still, validating other stuff can't be done to a decent extent without working system Ram.

[hawk]

Thanks very much for the replies. It gives me hope that I'll be able to get it up and running as soon as the IC sockets arrive. I'm hoping that the speed of the RAM chips isn't super critical, as I'm using some 100nS ICs from an old video card.

[+tf_hh]

In theory a diag mode cartridge could perform some rudimentary system validation tests without Ram - not sure if the SALT carts do any such thing but still, validating other stuff can't be done to a decent extent without working system Ram.

 

The CPS SALT cartridge has one error code for bad ram issues directly after boot-up - it shows a "System Failure #04" if memory is so bad, that the CPU´s stack can´t used. And the normal RAM test of course

[Rybags]

100 nS Ram should be fine. The max spec latency was supposedly around 250. By the time XEs came along the standard ones you'd get for OEM were something around 120-150 so they used them anyway.

 

I've also sourced Ram from video cards, probably got near 20 spare ICs and used a couple to do the 64K upgrade for my 600XL.

[hawk]

I wanted to follow up with the outcome of this repair.

 

Replacing the RAM chips worked fine. I now have another working XEGS. I got it hooked up with a disk drive and an SIO2PC and its great. Maybe I'll look at what other mods I might be able to make to this one.

 

I noticed on this http://atariage.com/forums/topic/258497-xegs-hints-for-repair/ thread mikro was having a similar problem, although his screen appeared differently to mine. I will now go and check out my power supplies to see that they're not causing the problem.

 

Thanks very much for your assistance.

Cheers.