Amiga 600 PCB corrosion from capacitors leaking electrolyte

[Per Hansson]

Hi, fixing up an Amiga 600 for a co-worker.
Caps C821 & C822 have leaked electrolyte causing the PCB to corrode.
You can see how it looked after desoldering the caps in IMG_6993
I have tried my best to clean it, the aftermath in the remaining pictures.

After this I've also tried baking soda mixed with water to stop the chemical process.
But I'm not sure if it's the best way, Googling gives very conflicting results.
I'm thinking of using Vinegar (acetic acid) but just wanted to ask first if there are any recommendations either way?

[llonen]

Re: Amiga 600 PCB corrosion from capacitors leaking electrolyte

I have used both with good success in the past, but for commercial repairs given the extent of the damage to the pads and some of the traces if this was a repair job I was working on the pads and some of the traces would be replaced.

[stj]

Re: Amiga 600 PCB corrosion from capacitors leaking electrolyte

i usually scrape off the laq and tin the nasty bits.

so now you need to see if you get get tants or poly's to fit on the pads.

[Per Hansson]

Re: Amiga 600 PCB corrosion from capacitors leaking electrolyte

Used acetic acid now, it sure worked allot better, I could see bubbles and hear fizzing as I put it on the areas with leaked electrolyte
After that I poured some distilled water over it, and finished with isopropanol alcohol and then a thorough run with an air compressor.

I could however see that under the choke it still looked like shit, and before I got a continuous stream of crud from there when trying to get a cotton swap under it.
So off it went, and oh my, that was a good idea.
I also removed the RF modulator, because I was not sure I got the area under it clean, but it was ok.

Next up will scrape the traces as recommended and apply some fresh tin, but that's for another day

[Topcat]

Re: Amiga 600 PCB corrosion from capacitors leaking electrolyte

Scrape the traces and tin them would be my choice as well. I've fixed a few like that over the years.

[petehall347]

Re: Amiga 600 PCB corrosion from capacitors leaking electrolyte

your pics are different places

[eccerr0r]

Re: Amiga 600 PCB corrosion from capacitors leaking electrolyte

looks a lot different with the common mode choke and the rf modulator removed, doesn't it?

Though I'm surprised, thought electrolytic capacitor electrolyte was usually some fairly neutral solvent, frequently organic; versus a battery which typically has some strong base in it that would eat aluminum.

[petehall347]

Re: Amiga 600 PCB corrosion from capacitors leaking electrolyte

i first saw pics 3 and 4 then saw later the other ones .. no doubt cleaner but not same places .. unless i am completely insane .. rectangles verses circles with holes .

[Per Hansson]

Re: Amiga 600 PCB corrosion from capacitors leaking electrolyte

They are of the same place.
As I wrote and eccerr0r also commented the pictures in my second post are with the RF modulator and choke removed.
Compare them with the first picture in the first post, and look at the only thing remaining: the power jack, than you will understand petehall347

It was surprising seeing the action of the acetic acid yesterday on component U12, there must have been allot of eletrolyte under it because it was really fizzing and bubbling
Attached a picture of it I took yesterday afterwards, looks like a bought one

[stj]

Re: Amiga 600 PCB corrosion from capacitors leaking electrolyte

i have to try that, i never used acid on electrolyte before - only battery crap.

[Per Hansson]

Re: Amiga 600 PCB corrosion from capacitors leaking electrolyte

Scraped the traces & retinned the pads and naked copper, and then new caps installed.
Boots up fine

RF modulator left out as the owner is thinking of installing a VGA port mod.
It's not like the RF modulator was useful anyway even when the thing was new!

Caps were bought by the owner, using this list: https://www.ikod.se/repairs/capacitor-lists/
I don't like the through hole caps, while the originals also were 10mm the hole spacing is 5mm and the circle on the PCB is for 8mm caps.
I would have used the ones listed below.
Anyway, it's a minor nitpick and those caps are newly launched by Panasonic, so probably didn't exist when that list was made

[B]Amiga A600 PCB rev 1.5 capacitor list:[/B]
Type		Specification	PartNo		Elfa PartNo	Count
SMD		22 uF 35 VDC	EEHZA1V220R	110-49-839	5 pcs
SMD		47 uF 35 VDC	EEHZA1V470P	110-49-841	2 pcs
SMD		100 uF 25 VDC	EEHZA1E101XP	110-49-836	4 pcs
SMD		10 uF 50 VDC	EEHZA1H100R	110-49-845	4 pcs
Through Hole	470 uF 25 VDC	EEUFR1E471YB	301-08-245	2 pcs
Through Hole	1000 uF 10 VDC	EEUFR1A102LB	301-08-232	2 pcs

[eccerr0r]

Re: Amiga 600 PCB corrosion from capacitors leaking electrolyte

Honestly the residue there does not look like the white corrosion caused by leaked electrolyte because of its behavior with stuff around there; rather I think something dried there and thus easier to remove. The brown junk however quite possibly is capacitor guts if it's not rosin, if it is truly water soluble capacitor guts, then that would easily explain the ease of cleanup.

I have never seen battery guts leaked out on the board cleaned up like that, nor water damage while the machine is on... You got lucky - just physical mess instead of a chemical mess.

[Per Hansson]

Re: Amiga 600 PCB corrosion from capacitors leaking electrolyte

It's the capacitors, there was liquid underneath them, however this was caught early.
It was only C821 & C822 that had leaked significantly, I used two irons to remove the caps.
It was no problem at all with all the other SMD caps, but C821 required allot of heat, so on C822 I cut it off instead.
That's the only area that was really bad, under the other caps in the same area there was just a tiny leakage so far.
If you do a Google search you will see that this is a super common issue with the Amigas (leaking electrolyte from the SMD caps).

Also the issue is hard to see, I have uploaded one more picture to the OP, it's almost impossible to see the damage in it, because it's localized under the capacitors.
All that's visible is that the solder pads for C821 & C822 are a bit dull.

I'm not sure what you mean with an easy cleanup, I had to use IPA, Acetone, Acetic Acid and finally distilled water then finishing up with IPA again.
This included lots and lots of scrubbing too, in all probably spent two hours in only cleaning the board.
Oh, and also the test with baking soda but not sure that did anything at all.
Or maybe you mean the stuff under the choke? Yea that could be something else, cleaned up easily with IPA and looked very different, could just be soldering flux maybe.
(Remember that the cleaning under the choke was done after the cleaning of the rest of the board had already completed).

[eccerr0r]

Re: Amiga 600 PCB corrosion from capacitors leaking electrolyte

impossible cleanup is if the electrolyte actually attacked the metal - the metal would be pitted and the soldermask damaged. Neither of these appeared to have happened.

[Per Hansson]

Re: Amiga 600 PCB corrosion from capacitors leaking electrolyte

Then you need to adjust your eyesight, like petehall347
For your reference, pictures can be clicked for higher res versions.
But I have uploaded crops of the relevant areas here, so you don't have to
The pads have been eaten away, only about 75% remain.

[eccerr0r]

Re: Amiga 600 PCB corrosion from capacitors leaking electrolyte

Nope, you were lucky. No solder mask damage except from your physical cleaning.

[sam_sam_sam]

Re: Amiga 600 PCB corrosion from capacitors leaking electrolyte

To me it looks like the out edges have been eaten way however I think you still have enough to work with but some how you need to make sure that t

[Per Hansson]

Re: Amiga 600 PCB corrosion from capacitors leaking electrolyte

Not sure why I'm even bothering replying here.
You've obviously decided there was nothing wrong with the board.
Maybe I should install the old caps back again, obviously they where not leaking eletrolyte.
That was eating the pads of the board, and starting to degrade the solder mask.

[petehall347]

Re: Amiga 600 PCB corrosion from capacitors leaking electrolyte

nice new ones and make sure they are connected ..