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Old 28 August 2019, 18:18   #1
Sim085
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Motherboard: Can someone help me understand what this is and how to clean it?

Hello, I have this a1200 motherboard (recapped) which I would like to clean up before I attempt any further repair works on it. I have been trying to clean it up with IPA. However I am not really doing much progress and when I check the motherboard from time to time it always looks worse off.

I understand there would be corrosion if caps had leaked (before recap), however there is what looks like dirt between chip legs and paula continues to shed something bluish even though I have cleaned with IPA over and over again. Some of the caps have a withish thing growing up (the caps of the other a1200 I have don't grow stuff like this so don't think it is the environment where stored).

Would anyone know what might be causing this? Is it just capacitor leak or there is more? (please note I did not buy this as new so don't know its full history, like something spilled on it etc.).

How can this motherboard be cleaned up?

Edit: Also just wanted to highlight how all soldering is dull, if I look on the back of the motherboard all soldering is still nice and shiny.
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Old 28 August 2019, 18:37   #2
Acill
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That is corrosion from a previous leak. The only real way to take care of it would be to remove the chips and clean under them and put new solder down. The next best method is to find a sonic cleaner and put the board in for a good sonic cleaning. You can also put it in a dish washer, but it may not help much with that level of corrosion.
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Old 28 August 2019, 21:50   #3
Sim085
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Once I remove the chips from the motherboard how can I clean them? Just IPA is enough?

With regards to sonic cleaning; is this an option to clean without disoldering all chips, or all chips still need to be removed before this can be applied?

Quote:
Originally Posted by Acill View Post
That is corrosion from a previous leak. The only real way to take care of it would be to remove the chips and clean under them and put new solder down. The next best method is to find a sonic cleaner and put the board in for a good sonic cleaning. You can also put it in a dish washer, but it may not help much with that level of corrosion.
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Old 28 August 2019, 22:03   #4
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Theres some great videos on YouTube by gadgetuk....he used a fiberglass pen.
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Old 29 August 2019, 00:14   #5
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When was the recap done? That C214 cap legs seems to be heavily corroded. I don't know what that white stuff on the cap could be, but it is not right!

How are you cleaning with IPA? IPA alone won't do much - you need a abrasive action too, like with a (clean/new) toothbrush, and even better with a pen style wire and/or fibreglass brush, and some kind of scratching tool.

This needs to be done several times to get a decent result. However, if there is corrosion under the legs and chips, it really needs to be removed to better deal with it.
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Old 29 August 2019, 00:23   #6
fxgogo
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I seem to remember Retro Man Cave using vinegar and a toothbrush. Could that be right? I have used it for leaking batteries to good effect.
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Old 29 August 2019, 00:49   #7
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I seem to remember Retro Man Cave using vinegar and a toothbrush. Could that be right? I have used it for leaking batteries to good effect.
Vinegar (acid) is used to neutralise the corrosive alkaline substance from a leaking alkaline battery (which an A1200 doesn't have), which in turn needs to be rinsed off with isopropyl alcohol.

Capacitor electrolyte leakage can be cleaned up with just isopropyl alcohol.

Both also needs some abrasive action for mechanical cleaning, along with the chemical cleaning.
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Old 29 August 2019, 08:00   #8
Sim085
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I took it for recap around two years ago. The person who did the recap did tell me that some caps around the IDE had leaked. Later it developed a sound issue so something else must have had leaked as well.

Quote:
Originally Posted by solarmon View Post
When was the recap done? That C214 cap legs seems to be heavily corroded. I don't know what that white stuff on the cap could be, but it is not right!
I mostly used IPA with cotton bulbs. I can't remember if I also used a toothbrush. Anyways, will give it a go with a new toothbrush to see if it improves.

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Originally Posted by solarmon View Post
How are you cleaning with IPA? IPA alone won't do much - you need a abrasive action too, like with a (clean/new) toothbrush, and even better with a pen style wire and/or fibreglass brush, and some kind of scratching tool.
The experience I had with this motherboard has pushed me to learn soldering so I can do things myself. I train on defective stuff I found around (mostly dead PC motherboards). I will use toothbrush with IPA to limit the advance of any damage there is. SMD caps I already have good results in removing so I might simply remove all of those to see what is going on under those.

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This needs to be done several times to get a decent result. However, if there is corrosion under the legs and chips, it really needs to be removed to better deal with it.
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Old 29 August 2019, 18:40   #9
jlin_au
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The electrolytic fluid residue from the leaking electrolytic capacitors is corrosive needs to be neutralized and cleaned up or it will keep corroding the exposed metal of the PCB traces and the other components on the motherboard.

In many cases the leaked corrosive electrolytic fluid residue will fluoresce under UV light and you can use a black light in dark conditions to see where the leaked electrolytic fluid residue is on the motherboard.

The audio circuits also pass their signals thru two polarized electrolytic capacitors (to decouple the audio DC signal to an AC signal) and can be also be affected if these capacitors leak. These AC decoupling capacitors can also fail and leak prematurely if the polarized electrolytic capacitors used are incorrectly connected with capacitor + side to - part of circuit and cap's - side on + side of circuit.

Suggest you soak the board firstly in demineralised water, gently clean any loosened corrosion off with a toothbrush, rinse in clean demineralised water. Repeat the soaking in Isopropyl Alcohol and repeat the cleaning and rinse in Isopropyl alcohol.

Using an ultrasonic cleaner with at least demineralised water for an hour or so would also be a great option.

Notes:
1) Isopropyl alcohol dissolves non-polarized compounds and will remove oils. However; it will fail to dissolve many salts and acidic or alkaline (polarized) compounds.
2) demineralised water is a better solvent for many salts and acidic or alkaline (polarized) compounds.

You also need to replace all the electrolytic capacitors on the motherboard or the issue will come back again.
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Old 30 August 2019, 10:53   #10
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Quote:
Originally Posted by jlin_au View Post
In many cases the leaked corrosive electrolytic fluid residue will fluoresce under UV light
Oooooh VERY interesting, I didn't know this!

I will definitely have a look at my A600 with this, I've recently purchased an multifunction torch that also has an UV mode, I knew it might turn useful sooner or later.
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Old 30 August 2019, 15:22   #11
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If you just had that recapped a couple years ago, whomever did it half-assed it. They didn't clean or neutralize the board. They may have even only replaced the caps that were visibly failing, so now you have new failures.
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Old 30 August 2019, 15:24   #12
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Quote:
Originally Posted by Turrican_3 View Post
Oooooh VERY interesting, I didn't know this!

I will definitely have a look at my A600 with this, I've recently purchased an multifunction torch that also has an UV mode, I knew it might turn useful sooner or later.
Yes, take a look sometime. It will be like a murder scene. You won't like it.
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Old 30 August 2019, 15:48   #13
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Well, since I have cleaned and recapped that unit, I hope I will (at least partly) like what I'm going to see.

I am NOT a pro though, so I guess there's room for improving my technique: UV light will hopefully help me see if/where I failed, that was my very first attempt after all!
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Old 30 August 2019, 18:19   #14
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Looks like it hasn't been recapped to me! You can clean up with white vinegar and cotton buds to neutralise the cap electrolyte, and then clean up with IPA and cotton buds. If you don't deal with it it will eat traces and kill the board (and possibly ICs). My advice if you haven't soldered before yourself is to contact someone on here (or amibay) that is recommended within the community. Or contact AmigaKit on their website. ie. to get it properly recapped.
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Old 30 August 2019, 19:53   #15
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Quote:
Originally Posted by GadgetUK View Post
Looks like it hasn't been recapped to me! You can clean up with white vinegar and cotton buds to neutralise the cap electrolyte, and then clean up with IPA and cotton buds. If you don't deal with it it will eat traces and kill the board (and possibly ICs). My advice if you haven't soldered before yourself is to contact someone on here (or amibay) that is recommended within the community. Or contact AmigaKit on their website. ie. to get it properly recapped.
As GadgetUK has said its probably worth getting it looked at by the professionals because I dont think it looks too healthy... I mean I could be wrong but in my experience when its grown fur its not good! I have had Steve from AmigaPassion do a couple of my 600's and he is really good I recommend giving him a shout.
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Old 30 August 2019, 22:24   #16
Sim085
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Yes, I saw his site and his FAQ is very helpful. I'll probably send him another A1200 I have which I do not dare touch myself.

With regards to this particular A1200; It was recapped but probably previous caps must have had already leaked and damaged something with the sound. Tried to get it repaired but to no use. Was close to throwing it away after seeing how it was degrading. I am now learning soldering myself (on bad PC motherboards) and at the same time I decided it would be nice if I get it to work again. Obviously first thing I need to get under control is the damage being done by those leaked capacitor. I still suspect some water damage as well. When I got this a1200 it had the metal shield rusted so I suspect some water must have made it through.

Quote:
Originally Posted by lord of time View Post
As GadgetUK has said its probably worth getting it looked at by the professionals because I dont think it looks too healthy... I mean I could be wrong but in my experience when its grown fur its not good! I have had Steve from AmigaPassion do a couple of my 600's and he is really good I recommend giving him a shout.

Last edited by Sim085; 30 August 2019 at 23:11.
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