Macintosh Plus corrosion : can I work it out ?

[mushanga]

Hi all,

I need advice to work on this initially good looking Macintosh Plus.
From the outside it was in good shape but once opened I saw the corroded chassis (photo 2).
Logic board is pretty good (photo 3) except for the serial ports zone (photo 1. It is AFTER cleaning with vinegar & IPA).
The good news is it starts up all the way through the blinking "?" but I cannot test it further without keyboard & mouse...
From what you know and see can you tell me how bad it is and if I can salvage it ?

Thanks in advance !

 

[Byrd]

The fact you’ve got it to boot without much of an issue tells me with some additional cleaning you’ll be good to go. The rusty coating on the PCB you can probably remove by spraying the areas with WD40, letting it soak in and use a cotton bud dipped in IPA to clean it. Take care around the traces and check continuity if they look suspect. The rust on the casing can be removed with a wire wheel easily enough.

 

[Berenod]

I hope foto 3 (the component side of the logic board) was before the IPA cleaning?
I usually flush with demineralized water, cause the IPA always leaves those blotchy white traces.
Just be very carefull everything is properly dry before powering up, unlike IPA water just doesn't evaporate that fast, and pockets of humidity can get stuck under components!

You'll have to test the traces to that connector for continuity, to me they seem to be eaten away, especially this one:

 

[cheesestraws]

This sounds totally salvageable to me. If it’s booting to a question mark, most of the computer is working properly. The LB on those things is also robust and chunky enough to repair straightforwardly so I think you are in with a very good chance

 

[mushanga]

Thank you all for your advices and support !
To Byrd : once I get some WD40 I'll try this.
To answer benerod : yes photo 3 is before cleaning (but after a small vacuum cleaner use to remove the spider webs from the inside !).
To be more precise, this cleaning was only a light one using Q-tip & toothbrush, first with vinegar (8°) and then with IPA.
I'm still wandering if soaking the full board in either demineralized water or IPA would do a better job with my photo 1 issue.
Also I'll probably end in desolder/unrust/resolder the "shield" on the analog board to stop the rust propagating.
I'll keep you updated with my work (might be in weeks/months though).

 

[ObeyDaleks]

In my experience, a dishwasher does an amazing job of cleaning boards. What I usually do is use a dry paintbrush all over the board, then a dry toothbrush on more stubborn spots. You'd be surprised how much rust a dry toothbrush can remove (rubbing very lightly). Then I throw it into the dishwasher, and usually the board comes out looking brand new. If there's more rust, I would then use WD40 on the problem areas, and back into the dishwasher. I believe that most dishwasher detergents also have some sort of rust prevention agent in them, which is an additional benefit.

P.S. If using dishwasher (or water in general), I usually blow it out with a compressed air to get water out of nooks and crannies, then wait 24 hours for it to completely try.

 

[dochilli]

I dry my washed boards in an oven at 50-60°C for half an hour.

 

[mushanga]

Just like that ? Dishwasher then dry (with or without oven) ? There is no risk of mineral deposit from the water ? Mine (water) is very "calcareous", almost in powder And I know the dishwasher salt should take care of that but still I wonder.
It would be practical though since I have no demineralized wate at hand for now... Need to find some WD40 too.

 

[olePigeon]

Dishwasher results can vary immensely. You could try it, but I've heard other people recommend against it. Some use enough pressure that they can break boards, knock components off, etc. And if you forget to turn off the dry cycle, it can further damage the motherboard.

Tap water can be fine, but you'll want to rinse it afterwards with distilled water (cheapest solution), deionized water, or isopropyl alcohol. This is to make sure it leaves no deposits that can cause corrosion or oxidation, especially if you have hard water where (I think) I read that the calcium can interact with old flux and create salt deposits (white powder.) I recommend warm (not hot) water with a bit of dish soap. Scrub it clean. Then follow up with a bit of vinegar around the capacitors and ICs to neutralize any electrolytics that may have leaked. Finally rinse with distilled or deionized water, or isopropyl alcohol. Set out to dry, perhaps next to a fan. If you're comfortable with the oven method, I suppose that would work, too. I'm very forgetful, so I'm terrified I'll forget about it and melt the board.

In my experience, hot water will melt the old, crusty flux and leave a horrible residue in random places all over the board. So I try to avoid doing that by using just warm water. It just becomes a pain, and you'll have to go back over the entire board with a q-tip and IPA to clean it off. But others may have had different experiences.

 

[3lectr1cPPC]

I’d absolutely recommend against the dishwasher. It could help but can also break already weak connections, and in a way that isn’t visible to the eye making troubleshooting afterwards very difficult.

 

[ObeyDaleks]

We’ll have to agree to disagree. I’ve been dishwashing boards since the 90s, and I never, ever, not once, had an issue. Not have any of my friends who have been doing the same. This was before the internet and the word of mouth among computer enthusiasts has always been that dishwashing boards is perfectly safe.

Of course, nowadays if you search hard enough you will find someone who reported issues with dishwashing but for the most part the consensus is that it’s perfectly safe for vintage and modern boards. There are a lot of opinions, but mostly from people who have never actually done it.

People with ultrasonic cleaners swear by those and you could argue that those are harder on the boards than dishwashers.

I’ve also never seen issues with old flux etc, if anything I’ve seen dishwashers get rid of stubborn issues at which other methods such as IPA have been marginally effective.

If you have credible examples of people damaging boards in a dishwasher, please feel free to share.

OP, not trying to convince you either way, please do what you feel comfortable doing.

 

[3lectr1cPPC]

I’m always open to varying accounts on what’s safe and what isn’t. And you’re right, I am just going off of what I’ve heard and I’ve never dishwashed a board myself. That’s largely because I’ve heard of the supposed negative effects before I ever had an instance where washing a board would be needed.
My main concern above damage, which I agree is unlikely (but possible - I’d guess it largely depends on how strong your particular dishwasher is) is contaminating dishes. I obviously wouldn’t run a board in with a load of dishes, but I also don’t really like the idea of mixing the area where cap juice and other crap like flux gets cleared off boards, and where dishes I’m going to eat from go. I’m no dishwasher expert, but I’d be worried it would linger. I’ve heard the same concerns from others as well.