Managed to bust an XEGS (Socketed CPU & PAL Antic)...

[cawley1]

All,

I had a non-working PAL XEGS (black screen), it had two socketed chips, though, so I thought I would try my luck by swapping out these chips. One is the CPU (C014806) and the other is PAL Antic (C021698).

I got lucky, and swapping the CPU brought it back to life and it booted into Missile Command.

 

However... I had also swapped the Antic at this point, and decided to put the original back in. Somehow I had both chips out the sockets again and (you can guess what's coming next) I switched the chips in the sockets. All that happened is I got a red screen, but the CPU chip in the Antic socket got very hot.

 

I realised pretty quickly and powered it off, but after swapping the chips back into the correct sockets all I now get it a red screen. I have tested the Antic I put in the CPU socket in another machine and it works, I have also tested the CPU I put in the Antic socket (the one that got hot) and surprisingly, that also works, but it's clear I have done something else to this PCB.

 

Anyone car to guess what I have buggered up? Is it likely to be the GTIA? I don't have great skills at deducing non-socketed chips, and would have to get someone to sort for me, but before I go throwing good money after bad, I figured I would ask if it's likely easy to work out what I would have done.

Thanks,
Paul

 

 

[Rybags]

In doing so you'd have a situation where there's outputs presented that should have been inputs, so potentially it could have fried something else.

If you have a static red screen then GTIA is likely fine.

Hard to say what could have been damaged, you might have to sit with pinout and schematics to work out what might have happened.

Could be something like OS Rom or might be something simple like a 74LS IC.  Or might be multiple failures.

[TZJB]

On 3/19/2023 at 11:57 AM, cawley1 said:

All,

I had a non-working PAL XEGS (black screen), it had two socketed chips, though, so I thought I would try my luck by swapping out these chips. One is the CPU (C014806) and the other is PAL Antic (C021698).

I got lucky, and swapping the CPU brought it back to life and it booted into Missile Command.

 

However... I had also swapped the Antic at this point, and decided to put the original back in. Somehow I had both chips out the sockets again and (you can guess what's coming next) I switched the chips in the sockets. All that happened is I got a red screen, but the CPU chip in the Antic socket got very hot.

 

I realised pretty quickly and powered it off, but after swapping the chips back into the correct sockets all I now get it a red screen. I have tested the Antic I put in the CPU socket in another machine and it works, I have also tested the CPU I put in the Antic socket (the one that got hot) and surprisingly, that also works, but it's clear I have done something else to this PCB.

 

Anyone car to guess what I have buggered up? Is it likely to be the GTIA? I don't have great skills at deducing non-socketed chips, and would have to get someone to sort for me, but before I go throwing good money after bad, I figured I would ask if it's likely easy to work out what I would have done.

Thanks,
Paul

 

 

 

I suspect that this may be a power issue.

 

Sally

1 Ground
8 +5V
21 Ground

 

Antic

1 Ground
21 +5V

 

Placing the Antic in the CPU socket would just make the refresh pin high so no damage there.

 

Placing the CPU in the Antic socket would short out the 5V supply, this is why the 6502 was hot. Check that 5V still exists to the Antic processor pin 21 as this may now be open circuit.