[vcf-midatlantic] Mac IIci, dead (PICS!)

Ethan O'Toole telmnstr at 757.org
Wed May 12 15:39:10 UTC 2021

> I'm a little confused by the telegraphic (short) descriptions that Ethan 
> gives for what he's repaired on and the symptoms of his IIci. (Hint: I think 
> his Mac may be running but it's not producing a VGA-compatible video.) Here's 
> the translation and the gloss to explain it.

Sup buddy! Yea sorry, I type fast.


> My read is: the Mac when bought, was dead, no power no video no audio. (Macs 
> "chime", a musical chord, on power up. He describes "chime" but maybe he 
> means "when the power button is pressed to start the Mac".)

Indeed! No chime!

> He then recapped the what? motherboard? power supply? - still no video or 
> maybe no audio. But he says he measures DC power.  The 68K Macs (ones with a 
> 68000 series processor), like PCs, operate the power supply from a start-up 
> circuit which is activated by a push-button to the motherboard (mobo) 
> starting circuit. There's a button on the motherboard, and there's also a 
> power key on the Mac ADB-type keyboards (as he describes).

Sorry, recapped the mainboard. The cap leak damage was minimal, no battery 
damage. I didn't touch the PSU, but I have measured it and everything 
seems good. This includes the 5v trickle that juices the soft power on 
keyboard functionality (which works!)

> There's a way to short two pins on the DC power connector to force the 
> power-supply to "wake up" - Web search for that. The IIci, IIcx and 700 
> models use the same power supply. Look it up.

Yea, I didn't need to go there because the power buttons work normally. 
Can turn it off using the rear button, can turn it on using the ADB 
keyboard or the power button on the mainboard.

> "screen is black, monitor wakes up" decrypts to "maybe my VGA monitor is 
> showing there's a signal, but it doesn't display it". That may be correct! 
> The Mac has a video connector which needs a quote "Mac to VGA adapter" which 
> mechanically rearranges signals but does nothing to them. The IIci native 
> video, is *not. VGA. compatible.*. The native IIci video (on mobo) however, 
> will never EVER run a VGA only monitor.  So it's possible the IIci is 
> producing a video signal.

Yep yep! I have one of those Mac DB-15 to VGA adapters. Actually a few of 
them. And the LCD I'm using which is some crusty 15" thing that clocks to 
ANYTHING goes from No Signal to black screen when it's powered on.

> On my Mac IIci, I have a Nubus video card and use that video for VGA 
> compatible results. The Macs "sense" which video connector (on mobo or NuBus)

Those are sexy! I used to have a bunch of Macs with them (IIx, IIci and 
others) but gave them all away years ago. They had Radius 21" monitors 
which were super heavy. Found at a biz Thrift store in Norfolk, used by 
the Daily Press newspaper in Hampton/Newport News based on the data on the 
hard drives.

> The circuits which produce the audio, tend to corrode out, from both the 
> failing electrolytics PLUS actual corrosion as a consequence of being near 
> the clock circuits. Huh? Well, the Mac time-of-day clock, has constant 
> battery power. That constant DC current creates a galvanic copper rust. Some 
> of that current "creeps" over to the audio circuits. There may be some audio 
> but it may be very quiet.

Battery is in great condition, the audio stuff is all in pretty good 
condition. Some slight scuzz on the pins of the two SMD chips near the 
modem/printer ports but I don't think it's bad.

Last night I found some IIci schematics, and was kind of surprised to see 
that the reset button appears to be routed through the Audio ICs? There 
are two SMD audio ICs, one for left and one for right. The PCB is pretty 
clean around those. The caps replaced by tantys by your's truely.

SOOOOO last night inbetween messing with the 35mm projector that isn't 
giving me audio... I managed to poke at it a tid bit.

I see NO activity on the data bus around the ROM chips. I don't think the 
CPU is running? I was looking at schematics cause I know the Atari 8bits 
have some kinda power on reset circuit... So far, all I found out is pin 6 
on the audio ICs from the schematics are labelled reset. When I hit the 
reset button it goes from high to low, then back to high again. I need to 
hunt down the 68030 reset lines I guess and figure out what state they 
should be in?

Also, I'm at work but I have pics from my phone of my sweet new IIci mobo. 
This is before recapping but you can see that the mainboard is pretty 


U83 is the Right sound chip, U-other-one is the other-one.

Of COURSE they're propritary. No data sheets from the googles.

Oh man, I just noticed in my picture.... RIP nubus connector corner. That 
will buff out.

> One can research these 68K Mac behaviors on the Web, and Apple had some 
> internal repair diagnostic documents, and "Apple service manuals" per model. 
> Look on the Web for these. But Apple did not document what happens 30 years 
> later; that gets described on the Web by those who repair these things. I 
> don't have much on Mac repairs on my site, I just sell Mac parts, like these.

Oooooo service manual you say? I found 3rd party schematics that shed some 
light on the reset functionality but it seems to mostly be reset-button 
functionality not any kind of power on reset.

There IS a chance that one of the vias is corroded from the cap juice and 
not passing signal. But none look bad and I ran a few out and they seemed 

Gonna try to find these troubleshooting docs! Thanks for the hads up on 

I hope it's detailed.

 		- Ethan

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