Help: possibly destroyed my A1200

[Marco]

While attempting to replace the original 3.0 ROM chips in my 1200 with some 3.1 chips I got from ebay I may have done something to fry my 1200. After we finished installing the new chips we attempted to power up the Amiga but nothing happened, none of the lights for power, f.disk or h.disk lit up, there was no activity from either the floppy or HD, nothing. We followed the instructions that came with the ROM chips to the letter, I even got an anti-static wristband just in case.

At first we thought it was a problem with the power supply but I tried the PS from our old A500, didn't work, then I tried the 1200s PS with the 500 which immidiately worked. So obviously that is not the fault.

We did remove the stickers that were on the ROM chips (they were stickers with Eyetech written on them and had instructions on which ROM chip was which (u6A and u6B) but we removed the stickers after installing the chips so there's no chance we put them in the wrong way round.

The 1200 is otherwise completely stock, no other mods have been made before. Does anyone know what the cause of the problem might be, and is it something reperable or is the 1200 dead?

[Marco]

Yes, I followed the instructions and made sure the notch in both was on the left (towards the PCMCIA slot) and that the contacts left free were also on the left. The ROMs themselves were also placed in u6A towards the bottom of the keyboard, u6B behind 'A'. I am too annoyed at this time to do any more, tommorow I'll try putting the 3.0 ROMs back in just to make sure. One thing that I did find odd - the ICs I got, they had a small, what looked like a 'window' in the centre, through which you could see the inner workings of some sort. Also they were manufactured by AMD, which I just thought was odd in and of itself.

I'll report back tommorow after trying the 3.0s. :-(

[Marco]

Sorry to do a bit of thread necromancy, but I was unable to work on the Miggy for a while as we had relatives round and I had to just leave the Miggy under the old dustcover from our 500 and forget about it. Anyway it transpired that the ROMs (or EEPROMS) work fine, I have no idea what the problem was still, but a few days ago I heard the drive-click while I was surfing the net on my PC, turned out I'd left the power on from an attempt the day before to get the Miggy functional again and through no effort my own it was now working, I plugged in the monitor and turned it on to see the purple boot screen with 3.1 ROM version 40.so on.

I then turned it off, closed up the case and screwed it all together, plugged the power and monitor back in and - nothing. Wouldn't boot, except now it would power up but the power light flashed and the screen displayed a single colour, sort of yellowy-greenish (I understand those one colour screens are an error message but I don't know what yellow means). Anyway, I again took the case apart and turned it on again, getting the boot screen perfectly normally, I came to the obvious conclusion that in shutting up the case I must have caused something inside to be pressed against something it shouldn't be pressed against, I screwed the case together while the miggy was on - VERY gently and carefully and it's worked fine since, installed Workbench 3.1 from the disks fine.

Anyway, it's caused not a single problem since, but from what you guys say I could end up with blank ROMs sooner or later, should I open it back up and cover up thw windows? It never comes into direct sunlight - during the day I either keep it under the dustcover, or if I'm using it then close all blinds in the room it's in to avoid sunlight contact with the plastic (I've read this is a cause of the yellowing that afflicts old computers but don't know if it's true, still I'm not taking chances)

Also, I'm suspicious that the metal shield may have been the reason for the problems I had, what exactly does it do? Can anyone give a brief explanation of why it's needed?