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Gabriele72
October 13th, 2012, 02:45 PM
Today I acquired an Apple lot which included a faulty Lisa 2/5 (the lot, for anyone curious, can be seen here http://museopc.blogspot.it/ ). I mainly bought it all because of the Lisa 2/5, I knew it was faulty but I already own a working 2/10 and that's a big help when trying to isolate a faulty board.

Well, after an afternoon of tests, I was able to determine that:

- The PS whistles a bit but seems to work OK, and so does the video.
- The RAM boards are OK.
- The backplane board shows a lot of corrosion, nevertheless it works, except for the external connectors.
- The I/O and CPU boards do not work ( :( )

The I/O board has the usual corrosion all around the (now removed) battery pack, the COP421 is OK but the LISA won't power on. I have a spare 2/10 I/O board I could use, still I would like to repair this one and not alter the LisaLite board near the drive. I don't know if there's a short somewhere or if the poweron signal isn't even reaching the COP. Half of the larger trace that runs below the battery pack and then on the right edge of the board has mostly "vanished".
Before I start wirewrapping everything perhaps someone might point me in the right direction concerning what to check first ?

The CPU board was the most puzzling surprise: the CPU was OK but the board was completely dead. I found out that:
- Someone has put a 74LS244 in place of the video ROM.
- The three 2148 SRAMs are socketed (no rework, they look factory socketed) and someone has put a 74LS21, 74LS02 and 74LS32 into them.
- The nearby 74LS245 is socketed too (a rework and not an amazing one).
- The ROMs are not 27C64 but 27C256 and not labeled. I'm going to make a dump to see what's in them.

All I could do was borrowing the EPROMs and the video ROM from the 2/10 and fitting three 2114 (no 2148 available). Teamed with the 2/10 I/O, the 2/5 now powers on but it only shows a white screen with retrace lines. The video ROM used is P/N 341-0230A and not the usual 0229A, don't know if this might cause some issue.
Any suggestion is welcome, for I'm stuck with this board too...

tezza
October 13th, 2012, 03:09 PM
Sounds like someone's messed with the CPU board not really knowing what they are doing at all!

I can only offer moral support. I managed to get both my Lisa's going. I was lucky though in that the I/O board in both Lisa 2/5 and 2/10 were ok.

If you think it would help, I could drag out my working I/O board and take close up photos around the area where the battery was?

Tez

NeXT
October 13th, 2012, 06:47 PM
I want to see pictures of this.
this sounds like the birth of one of those computer horror stories you hear floating around the net (like multiple disks in the drive or people not knowing that there is no ANY key).

Gabriele72
October 13th, 2012, 11:21 PM
Thank you Tez, I have found hires pics of the I/O board online, will look into that...
what could help might be the I/O board schematics.
BTW when you have time, could you please take a look at your CPU boards and note what SRAMs are fitted? 'Cause I'm not 100% sure the 2114 can fully replace the 2148 but if they happen to be found on one working board...

Also, if someone could burn me a 0229A video ROM I would really appreciate it , I think it's a TI PROM but maybe it can be replaced with something slightly more recent such as a PAL or an EPROM ?

@NeXT

I have removed the "alien" chips already, however get ready for more horror:
I dumped the EPROMs, among the hex pattern I was able to recognise:

68X80OR B OP 9118 62X0820 COPR. IBM 1985 :shock::shock:

tezza
October 14th, 2012, 12:24 AM
I have removed the "alien" chips already, however get ready for more horror:
I dumped the EPROMs, among the hex pattern I was able to recognise:

68X80OR B OP 9118 62X0820 COPR. IBM 1985 :shock::shock:

Wha ??? IBM lurking in an Apple Lisa ROM doesn't seem likely...

Sorry I don't have any schematics. However, I did check the SRAMS on the three working CPU boards I have. All 2148s I'm afraid :(

Tez

Compgeke
October 14th, 2012, 02:22 AM
Honestly sounds to me like someone got this scrapped originally and thought that because the chip fit it must work...I'm surprised nothing burnt up being as nothing really is correct here.

Gabriele72
October 14th, 2012, 11:43 AM
I have burned replacement EPROMs from the ones of the Lisa 2/10 (still I miss the video ROM), the CPU board could be working if I consider that the 2114 I used are much slower than the 2148, and if Apple chose 2148 there must have been a reason...

I couldn't find ROMs / PROMs dump online, those are vital chips to keep the LISAs working, someone could be interested in making a small dumping project complete?

Gabriele72
October 24th, 2012, 12:53 PM
Believe it or not, I have managed to get the I/O board working! :cool:
At least up to the point where the Lisa, borrowing a CPU board, now safely boots MacWorks XL and the keyboard responds (no speaker and mouse yet).
Schematics in one hand and multimeter in the other, I started checking ALL the connections between components, rebuilding with wirewrap the broken ones.
Seems the cure worked (I still have some sweat left, to anyone interested :D ).

I'm waiting for the 2148 RAMs to arrive... to see if the CPU board can be saved.
No video PROM yet... and still looking for someone with a spare TBP28L22, 82S135 or 74LS471 to burn :onfire:

tezza
October 24th, 2012, 03:11 PM
Well done! Sounds like it was quite a challenge so even all the more satisfying when you make progress.

Tez

Gabriele72
November 8th, 2012, 07:07 AM
Brought speaker and mouse back to life with more soldering, parallel port yet to verify... Still no sign of the RAMs I ordered to revive the CPU board... sunk into the Atlantic ? :confused:

Onward Lisa soldiers! :)

tezza
November 8th, 2012, 10:38 AM
No video PROM yet...

Are you still looking for a dump for this? If you can tell me exactly where the chip is and what the EPROM equivalent is (so I can configure the programmer) I might be able to read this for you.

Tez

Gabriele72
November 8th, 2012, 11:47 AM
Are you still looking for a dump for this? If you can tell me exactly where the chip is and what the EPROM equivalent is (so I can configure the programmer) I might be able to read this for you.

Tez

Thank you Tez, the PROM is usually a TBP28L22, it's a bipolar PROM and there's no EPROM equivalent, it can only be replaced by another TBP28L22 or a 82S135 or a 74LS471 which are compatible. Perhaps an EPROM could be adapted but I doubt any EPROM would be fast enough to work reliably.

After borrowing an old programmer at work I've been able to dump it (though I can't verify the dump is 100% OK for I've got nothing to compare it with...) mine is version 230 from the 2/10, yours is 229 or 230 ?