Lisa 2 Repair/Parts advice

[champagneandchips]

Hi there fellow Lisa (and other) aficionados!

I have started the journey of repairing a heavily battery bombed Lisa 2 (Frankenstein/modified model, it has an internal hard drive + a parallel port). Right now I am tackling the motherboard which has most of the damage, hoping I can get it back to working condition. Another forum member (rdmark, see the excellent write up of that member's repair journey) already gave me a few good tips and resources for replacement parts, and I've tried to do a bunch of research on filling in the gaps (I consulted this excellent forum, applefritter, 68kmla, and lisalist2 for the most part, amongst some more random and general google searches). Things I have done so far:

• vinegar bath and scrubbing
• needed to drill out a few screws as they were completely rusted over and could not be removed otherwise
• removed the badly corroded parallel, video, mouse and serial connectors (still working on the reset button which is stubborn)

The two large edge card connectors, which are losing contact pins fast, are next (I already have replacements for them). I'm working on removing some other damaged parts and more cleaning (this one will get a proper ultrasonic bath soon), and need some help identifying part types/specs please.

I found the (some) schematics here but I'm a) a complete novice when it comes to identifying passive components (or anything else to do with electronics, for the most part), b) no expert in reading schematics (I sometimes can't even tell the difference between a capacitor and an ibuprofen tablet ) , and c) if I'm reading this correctly, I'm not sure how accurate it is as there's some capacitors mentioned (specifically C3, C4) that don't exist on my version of the board, and it definitely seems to omit some of the parts I'm after (unless I missed something obvious).

Specifically:

• what are the black cylindrical and the round ceramic looking components marked L1-L11 (where my finger's pointing); I've seen some of them mentioned as inductors (with one 68kmla threadidentifying their value as 10µH) - am I right in thinking those are the black cylindrical components?
  • What are the ceramic disks that seem to accompany them 1:1? The writing on them says (provisional until I get something to magnify them better): COIM 25R (I've seen that spec used for resistors, but I also suspect those to be capacitors, not sure).
• specs for C12, which I assume to be a capacitor, also ceramic disk but larger than the others around L1..L9. The writing is so scratched up I can't identify what it says on it.

If anyone has any tips & tricks on how to identify these, or better sources for component lists in general (I'm sure I'll be back here with questions for other components anyway) let me know. Once I'm done with this, maybe I can compile a more complete list of all that's needed for others to follow in the future.

Thankfully the remaining boards are in much better condition, so I'm hopeful to get this back into working order soon (the condition of the hard and floppy drive remains to be verified)!

Thanks!

 

[Elemenoh]

what are the black cylindrical and the round ceramic looking components marked L1-L11 (where my finger's pointing); I've seen some of them mentioned as inductors (with one 68kmla threadidentifying their value as 10µH) - am I right in thinking those are the black cylindrical components?

That was my thread The black cylinders are indeed choke inductors and 10uH worked fine for me.

• What are the ceramic disks that seem to accompany them 1:1? The writing on them says (provisional until I get something to magnify them better): COIM 25R (I've seen that spec used for resistors, but I also suspect those to be capacitors, not sure).

From my restoration notes: 8x .001 uF 50v ceramic disc, +15% 85C

• specs for C12, which I assume to be a capacitor, also ceramic disk but larger than the others around L1..L9. The writing is so scratched up I can't identify what it says on it.

Can you point it out in a photo?

 

[champagneandchips]

That was my thread The black cylinders are indeed choke inductors and 10uH worked fine for me.


From my restoration notes: 8x .001 uF 50v ceramic disc, +15% 85C


Can you point it out in a photo?

Thank you so much for the details, much appreciated! I've attached a picture with the component I mentioned.

General update: it took me a while to remove both front edge connectors from the motherboard. There was so much corrosion I could not pry them off with heat so I had to cut away at them piece by piece, snip off the contacts and desolder them one by one. So much fun, I had to stretch it out over a week and a half. YouTube video about that to come soon!

 

[Elemenoh]

I can't find my notes for that one, but here's what I replaced it with. But I can't recall if it's 68pF (probably?) or uF or what voltage it's rated for. Sorry.

 

[champagneandchips]

Upon closer inspection with better light and some magnification (and cleaning), the smaller ceramic disk ones seem to say "001M" or ".001M" not "COIM", wouldn't that point to .001 pF not .001 μF ? The 25R could also be Z5R which seems more in line with temperature and tolerance specs - 5-85°C and +15% max capacitance change [ source ] (the things I learn while doing all this research! ). Remind me to make an appointment with an optometrist soon!

The larger one's (C12) writing is three lines, first line unclear but 48J or 68J (?), second line 600V, third line unclear N250 or N750 (?). That seems to line up with your suggested replacement of 68 pF and 5% tolerance. But does 600V sound right? And no idea what that third line indicates.

Regarding the inductors, Mouser has several sub categories (such as coupled, fixed etc.) - does this need a specific one of these or are they interchangeable (I would assume not but I have no idea what the actual differences are).

Thanks again for answering all those noob questions, really appreciate it!

[EDIT]

I measured a few of the ceramic disc ones, and they all seem to be in the region of 1nF confirming 0.001μF as you suggested originally.
Still not sure about which type of choke inductor to get. Mouse has different types and also seems to sub divide them by resistance and max current values, none of which I know.

 

[Markintosh]

This thread is inspiring! I just acquired a Lisa 2 in a similar condition. If you get yours working, there is hope for mine as well!