Macintosh II - Revival and overhaul

[LaPorta]

Hi everyone,

i have finally decided to haul out my Macintosh II, which I acquired on New Year’s Eve, 2000 (for a little background). It once worked, but slowly bit the dust about eight years ago. I finally have time, resources, and equipment to work on it.

first, I know I need new batteries. Second, a few traces appear damaged by cap goop. Third, all the electrolytic need replacing.

does anyone have a good diagram for what caps are what? The surface mount ones have no labels at all. Can’t start without that. Also, any good resource for replacing the soldered batteries with holders/ new 1/2 AA 3V ones?

 

[Unknown_K]

Is there writing on the yellow area around the middle of the capacitor?

 

[IIfx]

PCB looks good to me. My IIcx had the same caps. The values are printed on a yellow band around the side of the cap.

 

[LaPorta]

Note in the closeup the greened trace just to the top left of the yellow cap. I’m hoping that isnt oxidized beyond just a cleaning...it’s littlr things like that that I am talking about.

any suggestions on the battery replacement, good sized replacements?

 

[Zippy Zapp]

I see the corrosion on the IC legs next to the SMD cap in the close up but it doesn't look bad to me.   It probably just needs a cleanup with a brush and some Isoprop.  This board looks in much better condition then the Classic II I just re-capped, if that is any reassurance, and after re-cap and cleanup it now works fine.

As for the batteries, I don't know much about the Mac II but aren't these the same 3.6v batteries as just about every other Mac but soldered directly?  If so check the measurements for this part:

https://www.digikey.com/short/jd8772

See if those battery holders will work then just use the regular 1/2AA battery that we always use.

If they don't matchup you could just install wires between the board and the holder and velcro the hoders someplace.  I did this with a G3 Tower that had a corroded battery and I needed to replace and relocate the battery holder.  It also gets it off the logic board so if for some reason it ever leaked the board would be safe.

 

[LaPorta]

i am looking into the holders now. Interestingly, the batteries are 3V, not 3.6 V. I think i can locate some. Still 1/2 AA form factor.

Just ordered the caps as well. Each and every SM was 47 µf, 16 V. It's a pretty easy board to look into. I'll compile a list for everyone in case anyone else takes on a II.

 

[Zippy Zapp]

I love it when they are all the same!  The PM6100 is the same 47uf caps too.  I looked at the picture and that is exactly what I thought it would be because they looked the same in my situation.

 

[LaPorta]

Ordered the caps from mouser, should be here Thursday. The original SM caps I replaced with electrolytic polymer ones that are the same can style (I like things looking original). Reading up on it, it appears that they work the same way, but the electrolyte is a solid in the can instead of a liquid...so in theory the part should just fail someday, not leak all over the board. I’m not sure if they last as long, but this thing is a showpiece, not a work machine.

 

[Zippy Zapp]

Polymer caps will be better because, as you say they don't leak.  I have found that some are rated for very high hours life but some are not.  Usually they have a rating like 5000 hours @ 105c.  I have seen some that are rated for 10-15,000 hours.  But it seems usually they are in the 2000-5000 range.  My last few recaps I have been using high quality electrolytic that are rated for 10,000 hours.  They are 1/3 the price, or more, of the Polymer caps.  The also have hybrid caps too.  As far as I understand they are functionally equivalent to electrolytic caps, so you should be good.

Of course, just because it is rated for so many hours doesn't mean it is going to only last that long.  The ratings are if the cap is operated at that constant temperature.  Most of the caps in Macs, (with exception to  those near the power supply or CRT iMac caps) will not get anywhere close to that temperature and will usually be cool to the touch.  So that means that they will last many more times longer then what they are rated.

I think also this is why many people that do recaps use tantalum.  They won't leak either.  I, however, always do like for like. 

 

[LaPorta]

So it at least looks like the caps ate the crap out of a few traces. I tested the one by C19 with pins under the sound chip and I don’t find any continuity...but then again I have no idea where the things run without a full schematic. I don’t want to run new leads and misconnecr things. Anyone have suggestions?

 

[LaPorta]

Anyone hame Mac II Schematics?

 

[LaPorta]

So I found only one actual broken trace out of the lot thankfully. I repaired that with a single wire “stealth” run on the underside of the board. Made all the repairs, popped in new batteries, replaced the caps...and she works! Power via ADB and back switch, no problem. Now I need to tune up the floppy drives. Anyone ever replaced the caps on the floppy drives?

 

[techknight]

That trace is a common one. I saw it on mine as well. 

I am thinking about getting rid of my complete IIX machine. Shipping is the issue though.