68kMLA Classic Interface

This is a version of the 68kMLA forums for viewing on your favorite old mac. Visitors on modern platforms may prefer the main site.

Click here to select a new forum.
Mac LC II - Fault finding
Posted by: euan.webster on 2026-04-06 12:20:59 Hi all, Got an LC II. I repaired the PSU, and it's stable. Yellow screen on monitor (but the monitor also whines very high pitch when computer turned on, so not sure it's working either). No Apple bong noise. HD seems to power up and seeks, then nothing ROMs are (from left) - 341-0473 341-0474 341-0475 341-0476 1. Anyone know what to test the EEPROMS as on the T48 programmer? 2. Any other testing I can do? 3. Looks like a bit of cap gunk in rear right corner. These machines known for leaky caps?
Posted by: Phipli on 2026-04-06 12:38:57 Hi all, Got an LC II. I repaired the PSU, and it's stable. Yellow screen on monitor (but the monitor also whines very high pitch when computer turned on, so not sure it's working either). No Apple bong noise. HD seems to power up and seeks, then nothing ROMs are (from left) - 341-0473 341-0474 341-0475 341-0476 1. Anyone know what to test the EEPROMS as on the T48 programmer? 2. Any other testing I can do? 3. Looks like a bit of cap gunk in rear right corner. These machines known for leaky caps? Have you recapped the logic board? What state is the board in? Start from assuming it is cap damage and work from there. These machines known for leaky caps? Hell yes.
Posted by: euan.webster on 2026-04-06 12:54:21 Have you recapped the logic board? What state is the board in? Start from assuming it is cap damage and work from there. Hell yes. No, haven't done the board yet. Currently searching for schematic and/or list of caps :-D Sounds like I need to start there. I managed to read the ROMs as 27C010 with Pin Check and Check ID turned off, and they "seem" okay. Recap it is then!
Posted by: Phipli on 2026-04-06 13:09:37 Currently searching for schematic and/or list of caps :-D No need for either to start 🙂 the values are written on the caps, but here : Macintosh LC II (Performa 400) - Recap-a-Mac With 17 surface mount electrolytic capacitors that need replacing, you’ve really gotta love your Mac LC II if you want to keep it... recapamac.com.au Apple Schematic Archive - MacDat A complete archive of available board schematics for vintage Apple Macintosh computers. macdat.net Don't get too caught up in the schematics. Most faults are visible if you look at the board closely, so start with that. Look for damaged traces of a recap doesn't get it working. But I wouldn't blindly use the parts recommended by that site (just the values), in fact unless you feel like beeping out which cap is on the 12v rail, I'd just replace like for like with regular SMD electrolytics and not tantalums. Don't cheapskate and buy from a reputable seller, not eBay.
Posted by: euan.webster on 2026-04-06 23:05:45 No need for either to start 🙂 the values are written on the caps, but here : Macintosh LC II (Performa 400) - Recap-a-Mac With 17 surface mount electrolytic capacitors that need replacing, you’ve really gotta love your Mac LC II if you want to keep it... recapamac.com.au Apple Schematic Archive - MacDat A complete archive of available board schematics for vintage Apple Macintosh computers. macdat.net Don't get too caught up in the schematics. Most faults are visible if you look at the board closely, so start with that. Look for damaged traces of a recap doesn't get it working. But I wouldn't blindly use the parts recommended by that site (just the values), in fact unless you feel like beeping out which cap is on the 12v rail, I'd just replace like for like with regular SMD electrolytics and not tantalums. Don't cheapskate and buy from a reputable seller, not eBay. Thanks Phipli. I buy from Digikey or Mouser mostly, so will source from them. Much appreciated!
Posted by: Trianon on 2026-04-07 12:41:41 I can only confirm this, I had the same issue with an LC and LC II, recapping worked for the LC II. The LC would still not boot, one of the cap had leaked underneath the keyboard chip, so I desoldered it, cleaned PCB and resolder, done.
Posted by: euan.webster on 2026-04-07 12:58:22 Caps ordered from Mouser. I'll update when I get it done. Can anyone recommend a suitable display adapter for the LC II? Need to go to VGA or something vaguely modern as I don't know if my monitor is good or not. It's got a large hole in one side and whistles like a mad thing when it gets a signal!
Posted by: finkmac on 2026-04-07 13:02:16 i generally recommend a variant of this... but i use one of these more often. there's also this modern thing.
Posted by: euan.webster on 2026-04-07 13:05:58 Thanks @finkmac !
1