Poorly A1200 motherboard

Hi all, I've got a failed A1200 motherboard, it actually failed years ago and has sat in a box the entire time. I need to see if I can get it going now or it'll be dumped.

I've got it setup on my desk, PSU and video out are the only things plugged in. The power LED is blinking (well, fading) on and off twice a second, for about 3 seconds and then it pauses as the computer seems to reboot. The screen flickers at this point. This pattern keeps repeating.

The alice chip is the hottest, and I noticed that when I put my finger on it the LED sometimes stops flashing. I tried putting a little pressure on various points around the chip and sometimes I got a green screen, a yellow screen or a white screen. Usually it was just a black screen but without the LED flashing. Once it was the black screen but the LED was flashing a lot quicker. All of the capacitors look fine, no bulging or discolouration. There is a small dent on the crystal beside the ROMs but other than that the board looks perfect.

Does this sound familiar to anyone?

[Zetr0]

This could be a ROM fault
what ROMs do you have in there?


It could be a Power fault,
What PSU are you using?

They're the original 3.0 roms the board came with, never removed.

The PSU is a standard 25W commodore brick - I've tested this and it runs my A600 fine, and the voltages are stable when it's in the A1200.

[kipper2k]

Originally Posted by fsphil

Hi all, I've got a failed A1200 motherboard, it actually failed years ago and has sat in a box the entire time. I need to see if I can get it going now or it'll be dumped.

I've got it setup on my desk, PSU and video out are the only things plugged in. The power LED is blinking (well, fading) on and off twice a second, for about 3 seconds and then it pauses as the computer seems to reboot. The screen flickers at this point. This pattern keeps repeating.

The alice chip is the hottest, and I noticed that when I put my finger on it the LED sometimes stops flashing. I tried putting a little pressure on various points around the chip and sometimes I got a green screen, a yellow screen or a white screen. Usually it was just a black screen but without the LED flashing. Once it was the black screen but the LED was flashing a lot quicker. All of the capacitors look fine, no bulging or discolouration. There is a small dent on the crystal beside the ROMs but other than that the board looks perfect.

Does this sound familiar to anyone?

I had this problem when i removed Alice and put in a socket. Startup had random issues with different colour boot screens. i tracked it down to the chip not seating correctly in the socket so mabbe you have dry/cracked solder joints in that area. Don't dump it, if you give up i can make you an offer for the board.

Kipper2k, spot on! I heated a couple of pins about where the chip seemed to be most sensitive to pressure, and it lives!!!

I've never been so happy to see the insert disk animation ;-)

[kipper2k]

Originally Posted by fsphil

Kipper2k, spot on! I heated a couple of pins about where the chip seemed to be most sensitive to pressure, and it lives!!!

I've never been so happy to see the insert disk animation ;-)

Excellent! nice to hear, persistence pays off

So near, yet so far. Although the machine booted, there where quite bad glitches behind sprites. And a few days later it stopped booting again. So much for my soldering skills A bit of light pressure on the Alice chip gets it booting again...

I think it's time I got a Hot Air Rework station!

[cosmicfrog]

Like I say if it dos`n`t work hit it with a hammer LOL, nice pic, hope you get it sorted soon