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A few days ago I picked up some vintage apple Macintosh computers along with some vintage apple accessories and was ecstatic when the person giving me the computers said I could have their Macintosh IIfx in near mint cosmetic condition (besides some yellowing of the plastic) free of charge. When I got home however and opened the beastly machine I was presented with one of the worse cases of PRAM battery leakage I have ever seen. Both the PRAM batteries had leaked onto the motherboard and it was not pretty to say the least. Now I'm tasked with repairing my Macintosh IIfx

but I don't even know where to start. Any advice? Here's a picture of the leak before I started cleaning it:


Here's a picture after I got some of the gunk off (yes many parts fell off.):


Can I save this logic board? Will it take years, months, weeks, days? Is this worth my time. Is it impossible or possible but very difficult? I really don't want to see this computer go.

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My thoughts on this:


You're right, the leakage on that board is pretty horrible. I wouldn't write off repairing it as impossible per se, but it certainly won't be easy. IMO, given how rare and expensive working IIfx boards tend to be, it wouldn't hurt to at least try fixing it. It doesn't look like there are too many rotten traces, but I'd expect that there are quite a few. At the very least, components UD16, UF18, the 8530, the reset, interrupt, and power switches, battery holders, possibly the SIMM slot closest to the batteries, and most of the little SMD passives around them will need to be replaced.


In other words, given the cost of a new IIfx board, it wouldn't hurt to try fixing it, but definitely don't get your hopes up too high.

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Those images made my eyes hurt... The good news is that you can keep the near mint case and RAM and any other parts; you'll just need to find another II or IIfx board. But unfortunately that looks pretty bad; you'd need some serious electronics skills to repair the traces on that. If you're recapped stuff before you've got a fighting chance though.

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NoofleBot, I have a spare IIfx logic board, I keep it in case my IIfx has a catastrophic failure. I highly doubt it will die out of the blue though, as I recapped my main IIfx logic board last year and now it is rock solid reliable.

I'd be willing to sell the board to you, if your a collector and not a re-seller. The IIfx is my favorite Macintosh and I'd like to see the spare board go to someone who truly enjoys this system as well. It's better the spare logic board restore a dead system than sit in my office closet for eternity. I am about to recap that spare logic board, so if you do choose to take me up on my offer you will receive a board ready to take on the coming years. I won't sell it without the recap as it will just fail in the next 2 years without it.


Since your existing board has a good ROM SIMM and RAM you can re-use those. To fix the rust on the RF Shielding you can use rust converting paint, or remove that section of RF shielding entirely.


Even if your IIfx board is a total loss, there are valuable components on the board that can be salvaged and used to restore other dead systems. As is the dead board has little value. The 40mhz 68030 and FPU are worth pulling from that board, as are the custom Apple ASIC's.


40 minutes ago, Johnnya101 said:

If it comes to selling parts, I might want some ram. 


If I sell my spare logic board to NoofleBot, you can buy the spare RAM set from me. I am not sure as to the size.

Edited by IIfx
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I think  that board may be repairable.  There aren't that many traces over at that edge and the irreplaceable Serial PIC doesn't look damaged.  If the 85C30 is in too bad of shape, those chips are still available in the wild and not too hard to come by.    Finding exact/comparable replacements for the switches might take some work.   And there could be quite a lot of wire wrap in your future, but I think it is worth an attempt, if you are a patient person.


The 1/2AA battery holders are still available new too.   I can't make out/don't remember what UD16 is though.  As long as it's not a custom Apple chip you should be okay there.

Edited by trag
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Thanks for the advice! I'm going to at least attempt a repair on the board however I am new to repairing electronics, so new in fact that I don't even have a soldering iron (I'm looking into getting a nice soldering iron station). Of course I'll also have to learn how to solder first so that'll take some time. Addressing some of your questions / concerns:


Responding to "trag"

I was worried about the Serial PIC being damaged after I watched a video jason's macintosh museum made about the IIfx when he said something about that chip controlling all the I/O, luckily the chip appears to be okay, after cleaning the chip it had little corrosion left on the legs and the traces around the Serial PIC seemed to be attached to the legs. UD16 is D43256AGU-10LL which after cleaning was in rough condition, it had some missing pins/legs so I'm guessing I'll need a replacement for that if I want to attempt repairing the board.

I'm not sure which part you are referring to when you say 85C30. I have plenty of time to work on the board and I am a patient person, even if I do fail in repairing the board it will have still been enjoyable attempting to fix it.


Responding to "IIfx" (Very fitting name you have.)

Thanks for offering a replacement board just in case repairing mine doesn't work out. I do have a eBay which I occasionally sell vintage computers on but I'm not planning to sell my IIfx on there if I can fix the logic board or if I purchase a replacement from you. I think the Macintosh IIfx is a really cool machine, everything about it from it's looks to it's size and it's rarity is what really makes it special (also I love vintage computer workstations), I've always wanted a IIfx so If I can get this working I promise I won't sell it. I'm researching ways to remove the rust off of the shielding, electrolysis rust removal is interesting as it doesn't use any acids.


Responding to "Johnnya101"

If worse comes to worse and I can't fix the logic board I'll sell you the RAM, what do you need it for anyways? Are you just looking to upgrade your ram or are you missing ram? I know that the ram for the IIfx is rare as apple decided to use a special type to improve performance (also another reason why I love the IIfx, it's wicked fast as the code name would imply).


Responding to "jonpurdy"

Imagine how painful it would be to see those photos in 3D. Yeah, it sucks. My electronic repair skills are pretty bad besides using a screwdriver to replace stuff so I think the chances of me getting my IIfx working are slim but I might as well try.


Responding to "AwkwardPotato"

My hopes of cleaning the board in the first place weren't high to start with so if repairing the board doesn't work out I won't be disappointed. the SIMM slot closest to the PRAM battery holders actually is in great condition for how close it is, none of the electrical contacts have corroded and only the metal tab nearest to the batteries saw any corrosion. UF18 looks fine besides some corrosion on the legs, UD16 will definitely need to be replaced. Also I like your profile picture.


Once again thanks for the advice if you have anything else you can add to the conversation please do, also I'm most likely going to need a schematic of the logic board for the macintosh IIfx so that way I can order any of the parts that fell off.

Thanks again,



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D43256AGU-10LL looks like it is a generic SRAM chip, so you're in good shape.


This is the first Ebay result I found. There may be more affordable options:







If you don't have much experience with electronics, go slow and try to look up some of the older threads where SE/30s have been resurrected.  There are details in there about tracing connections with ohmmeters (DMM  -- Digital Multimeter) and bypassing open connections with small wires. 


Also soldering technique will be key for removing/replacing whole chips so read up and perhaps watch some Utube videos.   There have been several discussions on these forums as well.   But there's a lot of variation in servicable technique, so you'll find differing opinions on the finer points.


I think the 85C30 is the square chip about 1" on a side towards the edge of the circuit board from the endangered PIC.    If I'm wrong, then it is probably the 53C80, which is also available in the wild. and so not too difficult to replace.


Here is one of the threads of someone fixing a battery bombed logic board:



Edited by trag
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I guess now’s the perfect time for me to chime in. It took me years to fix this SE but I didn’t spend that many hours on it. 


I’d say this board is fixable. Definitely worth a try!

First things first, remove the Maxells (if you haven’t done that already)

Then I would limit the damage by neutralizing all that acid with white vinegar. Scrub it off with a toothbrush.

Acess the damage and order all the necessary chips/caps. It seems you’re somehow lucky as none of the Apple chips were harmed. 

I used a perfectly fine SE motherboard as a reference. I guess a schematic would have been fine but I find the SE schematics a little sparse... 

You’ll need a multimeter to buzz out the traces. If you find a bad one, patch it from the bottom side. I used old Dupont cables. 


That’s about it. Feel free to ask any questions. I too was quite a beginner (I replaced caps on quite a few boards) when I started this project. It felt really nice when the thing popped back into life. 


Don’t forget to post pictures as you go along!

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Looking at your board you'll need the following chips:

8530H-8JC Serial controller. Here's a few on alibaba. Might not be legit but worth a look. None are for sale on ebay...

D43256AGU-10LL SDRAM CMOS 'PRAM settings storage?'. 


Here are the IIfx's schematics: https://www.dropbox.com/s/5ljbh4z1z14su5e/Macintosh IIfx Schematic (bomarc).pdf?dl=0

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Responding to "BadGoldEagle"

I've already removed the Maxell batteries from the board and used white vinegar to clean off some of the corrosion (I wish I would have used a toothbrush, like you said). The Serial controller may not need replacing, one leg looks like it could be fully rusted but I don't think that's the case yet. I'm definitely planning on posting some pictures as I progress on the board I may even make a youtube video or two. I do have a multimeter which I haven't really used mostly because it's super cheap, it should work though if all it has to do is check if a current can pass through a trace. Speaking of recapping a board I also received a Macintosh IIci which has some leaky capacitors (just thought I'd mention it). Thanks for the link to the Macintosh IIfx schematic this should help me order parts. I may be getting some quadra's tomorrow and if any of them have leaking batteries I'll know what to do differently thanks to your advice on using a toothbrush to clean the board.


Responding to "trag"

I've been watching some videos on youtube about soldering (and the different types/methods) recently so I'm learning what I'll need to do to attempt a repair on this board. 85C30 / 53C80 appears to be safe.



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