Macintosh LC III

[KeithTilton]

I had a great package waiting for me on my porch today.

Found an LC III on Mercari for $40 + $30 shipping a week ago and decided to take the plunge.





No hard drive, the caps have just started leaking a touch but doesn't look like they've done any serious damage yet. I have a full kit of caps for both the motherboard and power supply arriving in a few days from Mouser.

Fortunately the battery was replaced at some point in the later 90's so it didn't bomb the board as well!

This is my first pizza box and I'm super stoked. I love the 68030 and 68040 machines so much.

Part of me really wants to power it up but I know better and should just wait until I get my caps...

Can someone identify the RAM in this? It's HY5117400B. It's 4Mx4 and there's 8 chips. That would make it a single stick of 16mb 72pin RAM right?

 

[cheesestraws]

Oh, nice. I like the pizza boxes a lot. Well found!

That would make it a single stick of 16mb 72pin RAM right?

Sounds right to me!

 

[joshc]

Nice score, another pizza box fan here.

Another thing you can do with these is to move R14 to R74 on the back of the board, this will turn your LC III into an LC III+, making the 68030 run at 33MHz instead of the stock 25MHz. It's a tiny bit fiddly if you're not used to dealing with small surface mount components but a worthwhile modification IMO.

 

[KeithTilton]

Nice score, another pizza box fan here.

Another thing you can do with these is to move R14 to R74 on the back of the board, this will turn your LC III into an LC III+, making the 68030 run at 33MHz instead of the stock 25MHz. It's a tiny bit fiddly if you're not used to dealing with small surface mount components but a worthwhile modification IMO.

Oh cool I had no idea that you could do this modification. I thought you’d have to replace the cpu. I will definitely be doing this mod once it’s up and running

 

[KeithTilton]

Welp, this sucks.

Two capacitors had their traces lift completely up while desoldering (C5 and C18). Looks like I'll be able to bodge a bit and get it working, but this was definitely not ideal.

Any advice appreciated.

 

[macuserman]

Did you use flux or just lots of heat to remove the caps? To much heat and that will lift the pads like that.

 

[KeithTilton]

Did you use flux or just lots of heat to remove the caps? To much heat and that will lift the pads like that.

340c and I used flux. I tinned my iron with leaded solder. I only desoldered four like that, those are the two that lifted. The rest I used the twist method and had a better time with.

 

[joshc]

I know you're not done yet but I see lots of cap gunk around the legs of the sound chip/DFAC - be sure to give that a real good clean! Problems with sound can usually be avoided by ensuring this area is cleaned thoroughly.



I personally use the unpopular twist method to remove caps and have never had a major problem with it; only a few lifted pads on very badly damaged boards. Be sure to put pressure down while you twist instead of up and only pull it off once the legs have broken free.

 

[KeithTilton]

Thank you. I definitely noticed that I need to scrub down the board in that area some more after it started drying. I scrubbed it about 10 minutes in the sink but it seems like it still has some more gunk on it.

I rarely lift traces twisting them. Seems like I lift them way more when I try and do it correctly.

 

[Juror22]

I used the twist method

I've been using this more and more lately, specially with the older boards. Some almost want to pop off when twisted, seemingly with very little effort. I also use cutting open the capacitor, then removing the legs by desoldering afterwards for those that don't readily respond to twisting. I think that it is handy to have more than one way to attack them and allow for a bit of flexibility, depending on how the capacitor and its traces respond.

I'm sorry that a couple of the traces on your board were lifted, but I agree that with a little bodge wire work, you should be able to recover completely.