Mac LC-II battery corrosion, will it ever run again?

[PhilC]

I've made a good bit of progress on the LC-II this week (especially since I've spent no time doing it).

I was struggling removing some of the corrosion from between the pins on the 68030 and a couple of the other chips. So I'd put the board into my Ultrasonic cleaner, well the bits that would fit anyway. And now it starts up and I eventually get the typical grey screen. No bong or drive icon etc yet though.

I also took the HDD apart and lets just say its beeping because its had it. There's visible corrosion on the plattens, possibly due to the acid, there's a mechanism where when running the plattens push the lever nd this unlocks the heads from their park position. This isn't moving. So That's one HDD died too.

I've put another HDD onto the computer and that's now allowed it to get as far as the grey screen.

So we are slowly getting there. Next will be me having to start coping out things.

[stephen_usher]

Sounds like potential ROM issues if it's not bonging or sad mac'ing. At least you're getting to the grey screen which suggests something may be trying to start.

[PhilC]

Sounds like potential ROM issues if it's not bonging or sad mac'ing. At least you're getting to the grey screen which suggests something may be trying to start.

Thanks for the suggestion, I’ll probably test them first as being DIP rims are easy to scope.

Don’t suppose you know what EPROMs replace them do you Stephen?

[stephen_usher]

I'm afraid not. You probably have to build an adapter to use EPROMs.

[stephen_usher]

Just checked, a 27C040 has the same pinout.

You can get the ROM images here: https://www.macintoshrepository.org/703 ... s-68k-ppc-

[PhilC]

@stephen_usher cool thanks

[PhilC]

Had a bit more time to do some fault finding tonight, which eventually ended up with me removing both oscillators and the 68030 cpu. Both oscillators had corrosion underneath them and the 25mhz one wasn’t working, so they were replaced with some from a spare but faulty board I had.

The 68030 was doing some really odd stuff, working when probed with the oscilloscope but not other times. Turns out there was more corrosion under it. When I removed the CPU about half a dozen pads came with it and this was with me carefully cutting off all the legs as I had a spare CPU to replace it with, so that’ll be why it was playing up.

New CPU fitted and tomorrow I’ll try and work out where the broken pads went to and fit a whole load of bodge wires.

It turns out that the grey screen I was getting on boot up was more to do with thr GBC than the max actually running, giving me some false hope. Now that both oscillators are working fine as are a few other bits I now have a proper synced screen. Although it’s a black one. So getting there, albeit slowly.

Good job this is just a practice adventure into corrosion repair and not an expensive old Atari or Amiga

[PhilC]

So I’ve cheated a little.

I got hold of a second LC-II that also didn’t work and have now managed to get that to boot. I’ve just loaded up an image on a BlueSCSI and it’ll boot to desktop.

So now that I have a fully working LC I can use it and it’s roms as reference for the one with the corrosion repair. I’m pretty confident that once I get the bad tracks on the CPU sorted we should be there or at least very close.

The second LC had an oscillator fail and the VRAM and HDD had failed. I did use my recapped PSU so better do the same to the one from this LC in case that’s what killed a few bits.

[rubber_jonnie]

So I’ve cheated a little.

I got hold of a second LC-II that also didn’t work and have now managed to get that to boot. I’ve just loaded up an image on a BlueSCSI and it’ll boot to desktop.

So now that I have a fully working LC I can use it and it’s roms as reference for the one with the corrosion repair. I’m pretty confident that once I get the bad tracks on the CPU sorted we should be there or at least very close.

The second LC had an oscillator fail and the VRAM and HDD had failed. I did use my recapped PSU so better do the same to the one from this LC in case that’s what killed a few bits.

Always good to have a working spare

[PhilC]

@rubber_jonnie I was just surprised it all worked with the Blue Scsi so easily