MAC IIci chimes but black screen, any ideas?

[Glen M]

I've been working on a MAC IIci for the last couple of weeks that was sent my way for the price of postage only as it was heavily battery rotted. The former owner had a go but was unable to get any life out of it. I've been over it in fine detail and repaired maybe 30 traces, its finally showing some signs of life but little else. Currently when powered up it chimes and gives a black screen. If I remove one of the ram simms it plays a different chime (death chime?) and again just sits at a black screen.

I don't know much about apples but I've been told this is sign of it booting but its failing it hardware tests before it can show a sad mac. I've tried other ram simms although one thing I'm not sure of is does the mac need a certain type of ram? The other simms I used are just out of an old PC.

The board was recapped by the previous owner although I've been over this work and while it needed tidied a bit it wasn't bad. I don't see anything broken or damaged at that end of the board, it was just around the battery area.

I've tried it on both a VGA monitor using a home made cable and my old MAC CRT, the crt is just a pain to use since it so large, but in both instances the result is the same. The LCD reports its receiving a 640x480 66hz signal so I think that's working ok.

I appreciate its not a lot to go on but if anyone had any ideas of things to try in my attempts to repair this machine then please let me know.

One question, to test the rom chips I was going to read them out in my TL866 but what would be a compatible eprom? They are 32pin dips and I think 8x512?

Couple of photos from work in progress. It has obviously moved on from when these were taken with the remaining parts fitted and a few more patch wires run. Most the patches are hidden under the sockets, in the most part the damage was traces disconnected from their hole. Basically anywhere you see copper was more or less green from battery rot.


top side bottom side

 

[3lectr1c]

The issue with these battery bombs is that even if you repair every single visible damage point, there’s a large chance some internal via or track on one of the internal layers of the board has been damaged, in which case, good luck fixing that. Not much you can do in that case.

 

[GiGaBiTe]

Currently when powered up it chimes and gives a black screen. If I remove one of the ram simms it plays a different chime (death chime?) and again just sits at a black screen.

You receive a death chime because the bus is trashed. Memory must be installed in groups of four per bank, if you remove one, part of the bus is left floating.

The 68030 is a 32 bit CPU. The Macintosh IIci uses 30 pin SIMMs, which are 8 bits wide, and requires SIMMs to be installed in groups of four. The IIci has two memory banks, 4 slots on the left and 4 on the right. It will accept 256k, 1M, 4M and 16M SIMMs for a maximum of 128 MB of RAM. All memory modules in the same bank must be of the same type and capacity. They must also be verified good. If you don't know if your memory sticks are good or not, I'd recommend putting them back in the PC you removed them from and running an older version of Memtest on them. You can't mix and match memory module capacities in the same bank.

They also must be rated at least 80ns or faster.

I don't know much about apples but I've been told this is sign of it booting but its failing it hardware tests before it can show a sad mac. I've tried other ram simms although one thing I'm not sure of is does the mac need a certain type of ram? The other simms I used are just out of an old PC.

There are definitely Macintosh models that require special or proprietary memory modules, but the IIci isn't one of them. As long as the memory modules are 256k, 1M, 4M or 16M, are 80ns or faster, and are FPM, they should work. Additionally, you may need 8/9 chip modules vs. the later 3/4 chip modules. The row and column layout of the memory on 8/9 chip and 3/4 chip modules can be different, and will cause problems on some Macintosh models, like the SE.

Just remember that there are two memory banks of four slots each, and that each bank must be fully populated with the same type and capacity of memory module, you cannot mix and match them. I believe they're labeled as Bank A/B or 0/1, and you have to populate the lowest bank first.

One question, to test the rom chips I was going to read them out in my TL866 but what would be a compatible eprom? They are 32pin dips and I think 8x512?

I believe that the stock ROMs are Mask ROMs, not EEPROMs or EPROMs. Without seeing a picture of them, no idea. But many Macintosh models split the ROMs even and odd bytes into different chips, so you couldn't just burn one ROM and call it a day. I think there's a pinout difference between the Mask ROM and an EPROM/EEPROM, so you may have to build an adapter to use them.

 

[Glen M]

Thanks for the info.

In terms of internal layers I thought it might only be ground and vcc. I have found missing ground just at the battery itself but that has been repaired. If there is internal signalling then its probably game over.

As for the RAM thing, I should have explained it better but yes I understand the requirement for 4 simms and that they are in 2 banks. My comment about removing one to force the death chime was more about proving that with the mac doing that it is at least running to some extent. Thanks for confirming though that the ram modules are just standard although the alternative 4 sticks I tried were the type with 3 chips on them each so maybe there is still a ram issue. Easiest thing to do would be to take the 4 simms from the MAC and try them in an old PC.

Yes the stock roms are mask roms, I didn't know there would be a pinout difference between those and whatever the compatible eprom may be. The roms chips were badly corroded, I lost pins on them while desoldering although that has also been repaired. But it is an area of concern that there may be issues with them. Its a 512k rom file and presumably 32bit hence my thinking that with 4 roms they must each be 8x512.

I'll test the ram and other than a possible failure there I think I might just have to call time on this one for now. If I had another good machine it would be a lot easier to diagnose but unfortunately thats not an option.

 

[GiGaBiTe]

In terms of internal layers I thought it might only be ground and vcc. I have found missing ground just at the battery itself but that has been repaired. If there is internal signalling then its probably game over.

I'm not sure how many layers the IIci uses, other Mac boards of the time used either 4 or 6 layers, so it could be either. I saw on the bodge wires on the bottom of your board where it looks like two of the wires are bridged together with solder, not sure if that's a problem or not.

Yes the stock roms are mask roms, I didn't know there would be a pinout difference between those and whatever the compatible eprom may be. The roms chips were badly corroded, I lost pins on them while desoldering although that has also been repaired. But it is an area of concern that there may be issues with them. Its a 512k rom file and presumably 32bit hence my thinking that with 4 roms they must each be 8x512.

You'll need to cross reference the ROMs you have vs an EEPROM/EPROM replacement, wouldn't be a great idea to just shove in any 32 pin ROM.

As for how the ROMs are laid out, not sure really, you'd have to trace the data bus pins. Many Mac models of the time just had the ROMs ordered as 16 bits wide, even on 32 bit machines with a 68020/030.

I'll test the ram and other than a possible failure there I think I might just have to call time on this one for now. If I had another good machine it would be a lot easier to diagnose but unfortunately thats not an option.

In the future, there may eventually be a logic board replacement available. The Mac community has been hard at work reverse engineering older Macintosh PCBs and having new logic boards produced to replace ones that have been battery bombed. There are already several models that have logic board replacements available, and it looks like the IIci may be worked on at some point soon. So even if your board is dead, save it for parts so you could eventually transfer them over.