Mac LC II - Fault finding

[euan.webster]

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?

 

[Phipli]

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.

 

[euan.webster]

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!

 

[Phipli]

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.