• Updated 2023-07-12: Hello, Guest! Welcome back, and be sure to check out this follow-up post about our outage a week or so ago.

My first Apple computer, a Mac IIcx

rodders

Member
Well I've pulled it apart and it ain't pretty.
The PRAM battery has completely destroyed the battery holder contacts.
It looks like it was stored on its side, which is probably good because its done the least amount of damage (but bad enough) - imagine the damage to the simms if it had been the other way up. It was also damp because there are lots of rusty bits. I've got my work cut out on this one, but hey, it was cheap.
The PSU is an Astec AA15830 it looks pretty grotty but I haven't delved inside yet.
The floppy drive is full of fluff and dirt. It looks a pretty flimsy affair with only a plastic sheet instead of a metal case. I'm not overly impressed with Apple quality considering how much this thing cost when new.
The simms picture isn't too clear but the DRAMs are TMS4C1024 so that makes them 1MB, 4MB should be enough to get started.
So, a bit of a clean up next but what to do about the battery holder? I presume you can't get them any more and it would probably be better to fit a remote battery anyway - suggestions?
Thanks to joshc I have schematics now but is there a PCB layout schematic to help find parts that have no silk screen?
Thanks to all of you who have commented, its great to know there is help out there.
 

Attachments

  • IMG_20230730_095321475_HDR.jpg
    IMG_20230730_095321475_HDR.jpg
    5.9 MB · Views: 18
  • IMG_20230730_095740138.jpg
    IMG_20230730_095740138.jpg
    3.8 MB · Views: 19
  • IMG_20230730_095342750_HDR.jpg
    IMG_20230730_095342750_HDR.jpg
    3.8 MB · Views: 17
  • IMG_20230730_095407285.jpg
    IMG_20230730_095407285.jpg
    1.6 MB · Views: 13
  • IMG_20230730_095424250.jpg
    IMG_20230730_095424250.jpg
    1.5 MB · Views: 13
  • IMG_20230730_100420696_HDR.jpg
    IMG_20230730_100420696_HDR.jpg
    3 MB · Views: 13

Phipli

Well-known member
The floppy drive is full of fluff and dirt. It looks a pretty flimsy affair with only a plastic sheet instead of a metal case.
Its going to be a Sony drive, wouldn't have been that budget. Weird though, all of mine have a steel housing?
So, a bit of a clean up next but what to do about the battery holder? I presume you can't get them any more and it would probably be better to fit a remote battery anyway - suggestions?
Just leave it out for now. You don't need a battery. Most of us run machines without batteries... You might guess we have battery hate and they're not as needed as in an Acorn... Although I run my A3010 without a battery and boot holding copy and shift with a boot script that sets up my IDE podule.
Thanks to joshc I have schematics now but is there a PCB layout schematic to help find parts that have no silk screen?
Yesssss... Give me a minute
 

Phipli

Well-known member
Reverse engineered board here - you can open the Gerbers in a viewer and if you use the right one, it will even highlight connected copper.

 

Phipli

Well-known member
Well I've pulled it apart and it ain't pretty.
The PRAM battery has completely destroyed the battery holder contacts.
It looks like it was stored on its side, which is probably good because its done the least amount of damage (but bad enough) - imagine the damage to the simms if it had been the other way up. It was also damp because there are lots of rusty bits. I've got my work cut out on this one, but hey, it was cheap.
The PSU is an Astec AA15830 it looks pretty grotty but I haven't delved inside yet.
The floppy drive is full of fluff and dirt. It looks a pretty flimsy affair with only a plastic sheet instead of a metal case. I'm not overly impressed with Apple quality considering how much this thing cost when new.
The simms picture isn't too clear but the DRAMs are TMS4C1024 so that makes them 1MB, 4MB should be enough to get started.
So, a bit of a clean up next but what to do about the battery holder? I presume you can't get them any more and it would probably be better to fit a remote battery anyway - suggestions?
Thanks to joshc I have schematics now but is there a PCB layout schematic to help find parts that have no silk screen?
Thanks to all of you who have commented, its great to know there is help out there.
Looking at the battery damage that's fairly rough. How much PCB repair experience do you have?

@joshc is that worse than mine was before cleaning?
 

rodders

Member
I've been cutting my teeth on an Acorn RiscPC. So far I've had to fix the traces and replace components in the battery area, including the CMOS chip, several other ICs around the board. Still tracking down the problem of no mouse buttons...
 

Phipli

Well-known member
What an amazing piece of work that is!
When you live in a world with so many capacitor and battery ruined boards, you need people like @max1zzz :)

It means as long as the custom chips are OK, you can move to a new PCB in the worst instances.

It needs to be pretty bad before you consider that though.
 

cheesestraws

Well-known member
It looks a pretty flimsy affair with only a plastic sheet instead of a metal case

Less flimsy, more badly-thought-through. The drives themselves are pretty robust, but somehow it never occurred to anyone that they might fill up with fluff until rather too late. I do wonder whether Apple omitted to tell Sony that the floppy drive slots were part of the ventilation design in these cases... The plastic dust cover was a retrofit, IIRC—later Mac drives had metal cases like PC ones.

In general, though, you will find that Apple construction is a bit less robust than Acorn construction, because the impetus of "nearly every machine we sell will be being bounced up and down on by children for its entire working life" wasn't there. Different tradeoffs.

So, a bit of a clean up next but what to do about the battery holder? I presume you can't get them any more and it would probably be better to fit a remote battery anyway - suggestions?

The battery is a standard half-AA size part and new batteries and holders are pretty readily available. That said, because MacOS is highly disc-based (unlike RISC OS) far fewer of the settings that matter are stored in battery-backed RAM. The only really annoying ones are the time, the default network interface and 32-bit addressing mode (which allows addressing of more RAM), and there are workarounds there (I use network time sync, for example). Personally, I don't bother with PRAM batteries in most of my Macs.
 

croissantking

Well-known member
Yes, but something like PRAM Auto-Restore will deal with that. The three I listed can't easily be reset just by keeping your PRAM on disk and restoring it at cold boot.
That’s true.

Though I haven’t had great results with PRAM Auto-Restore - it seems to introduce other problems.

I run my desktop macs with a battery, it’s my PowerBooks that I have trouble with - I can’t seem to get them to hold their settings even with a rebuilt clock battery.
 

joshc

Well-known member
@joshc is that worse than mine was before cleaning?
Worse I think. But... the battery damage in the pics above is not the worst I've ever seen.

4MB should be enough to get started.
Yeah 4MB is very decent especially for System 6.

The PSU is an Astec AA15830 it looks pretty grotty but I haven't delved inside yet.
There are other options you can explore later on, if you decide you don't want to repair the Astec unit. I put an ATX PSU inside the original enclosure before.

The floppy drive is full of fluff and dirt. It looks a pretty flimsy affair with only a plastic sheet instead of a metal case. I'm not overly impressed with Apple quality considering how much this thing cost when new.
It appears to be missing the metal shield/cover around it - someone must've been lazy enough to not put it back on. The Sony drives are really high quality and are good drives, when they work.

So in this pic:
1690734439524.png

Those capacitors, and the logic gates next to them, and those diodes, form part of the startup circuit. This area around the battery does need to be repaired in order to get the machine to start, at least if you want soft power to work.

I might be stating the obvious here - but replacing the HC132s and HC74 and diodes with new components is going to be the way to go - the ones on there look toast.
what to do about the battery holder?
Remove it, and keep it that way, unless you are bothered about the machine keeping its own time. There are other ways to get it to keep time without the battery though. The battery is not needed for the computer to work.
 

LaPorta

Well-known member
Not sure why everyone is deathly afraid of these PRAM batteries. If any of mine are toasted, I always replace the holder and put in a new battery. You’re not (I’m assuming) going to stuff it in a closet for twenty years and let it happen again. The time will no longer be held properly when you start the machine before the thing explodes, and you can change it then.
 

LaPorta

Well-known member
If your drive has the plastic, it may have come that way factory. Most of the Sony drives don’t have anything covering them on all the older machines, and that is normal.
 

cheesestraws

Well-known member
Not sure why everyone is deathly afraid of these PRAM batteries.

tbh, for me, it's just one less thing to be neurotic about. And I'm sufficiently neurotic that one less ground for worry is valuable, even if it's not strictly speaking necessary or useful :).
 

Phipli

Well-known member
Not sure why everyone is deathly afraid of these PRAM batteries. If any of mine are toasted, I always replace the holder and put in a new battery. You’re not (I’m assuming) going to stuff it in a closet for twenty years and let it happen again. The time will no longer be held properly when you start the machine before the thing explodes, and you can change it then.
They're not needed is why we mostly leave them out. We're not all deathly afraid of batteries, just there is no point in the small risk, given all I need to do is set my mouse speed. I have batteries in machines I use often.

Don't confuse three people agreeing with some crazy fear.
 

rodders

Member
I might be stating the obvious here - but replacing the HC132s and HC74 and diodes with new components is going to be the way to go - the ones on there look toast.
I'm trying to put a list of parts together for the startup area. I've found most of them but I'm missing
  • UM5 - looks like an Apple specific clock IC
  • Y4 - presumably a crystal for the clock
  • F3 - a fuse?
Is there a complete parts list anywhere or does anyone know what these part are?
I guess I've been spoiled by the Technical Reference Manual I've been using for the Risc PC!
 

joshc

Well-known member
Not so much that as what I’ve seen for years from others, too. Obviously it’s whatever you guys think is best for your machines.
It’s too easy to forget a battery in a machine. I’ve had newer batteries fail and leak, so it’s not entirely impossible to have issues even if you regularly check. The benefits are slim too, the few settings stored in the PRAM are not that important to warrant keeping the battery in my opinion.
 
Top