Leaked Battery Motherboard Repair

[XsamX1987]

Hello every one so my friends dad gave me an old computer its from 1990 or 1993 any way I spotted a leaking battery so I disordered it nd there is some damage so I had to remove the din connecter and where the mother board connects an old school 12pin I did this so I could see how far the damage has gone

I'm looking for advise for the lines and tracers as I'm still getting continuity but I can see the corrosion I've cleaned the area with rubbing alcohol and I've scratched off a little of the rust/oxidation

What is a good and simple way to fix this

I am very new to this and my skill level is low

tools and parts available to me

20 watt soldering iron

solder

kynar wire

solder wick/braid

rubbing alcohol

tooth brush

a chap digital multi meter

The back you can see the very bad job I did here




The front

 

[kellys_eye]

Ideally you would use a continuity meter and trace the path of the copper track to points at either end where the corrosion is not apparent and then check that the path between those two points is continuous.

On your picture I see that pin 2 of the DIN socket has a track that goes via L3 then off to the right somewhere (off picture). So measure between pin 2 and where ever that track ends up to ensure continuity. If you can't measure it then you have to solder a wire link between the two points instead.

Note that L3 (and L2) are simple ferrite beads over straight wire so have no (or very little) resistance and can thus be considered as 'short circuit' for the purpose of continuity testing.

note that those motherboards are MULTI-LAYERED and tracks can disappear through those holes to a hidden layer and reappear elsewhere. Also, desoldering from multi-layer boards needs to be done with extreme care as it is easy to strip the thru-hole plating that interconnects the multiple board layers - in which case the board will be ruined beyond repair.

Your board doesn't look too bad - if the tracks from the 'top' of L2 and L3 are ok then simply cleaning up and resoldering should fix it - assuming there's nothing else wrong around the board....

Use IPA (Isopropyl Alcohol) to clean the flux residue. Try to avoid 'scraping' the corrosion.

 

[XsamX1987]

Thank you for Helping me

So Because its Multi-layered removing the components I might of damaged it even if it was working ?

Ok I had scraped away some of the corrosion I will stop doing that

cleaning up with IPA will that also neutralize the corrosion

ok so far there are only a few points I cannot get continuity

Din 2 to c86 is fine but Dine 2 to L3 there isn't any

Din 1 to L2 is fine but then Din 1 to c87 same as before isn't any

Then the Tracks where the main corrosion is there all fine

once I have cleaned the tracks do I coat them in any thing for protection like Clear nail varnish

and how hard do I clean the corrosion and green/blue residue do I say use a cotton bud or IPA on a hard tooth brush ?

I will include a better picture

Ideally you would use a continuity meter and trace the path of the copper track to points at either end where the corrosion is not apparent and then check that the path between those two points is continuous.

On your picture I see that pin 2 of the DIN socket has a track that goes via L3 then off to the right somewhere (off picture). So measure between pin 2 and where ever that track ends up to ensure continuity. If you can't measure it then you have to solder a wire link between the two points instead.

Note that L3 (and L2) are simple ferrite beads over straight wire so have no (or very little) resistance and can thus be considered as 'short circuit' for the purpose of continuity testing.

note that those motherboards are MULTI-LAYERED and tracks can disappear through those holes to a hidden layer and reappear elsewhere. Also, desoldering from multi-layer boards needs to be done with extreme care as it is easy to strip the thru-hole plating that interconnects the multiple board layers - in which case the board will be ruined beyond repair.

Your board doesn't look too bad - if the tracks from the 'top' of L2 and L3 are ok then simply cleaning up and resoldering should fix it - assuming there's nothing else wrong around the board....

Use IPA (Isopropyl Alcohol) to clean the flux residue. Try to avoid 'scraping' the corrosion.

 

[kellys_eye]

Simply removing parts from a multi-layered board doesn't necessarily mean its death knell! It's quite possible to remove parts without causing damage but once damage HAS occurred it's nearly impossible to fix. You can tell if you've caused damage as the thru-hole plating tends to remain on the removed component pin/lead and can be seen quite clearly. Time for a few sobs.....

I can see corrosion on the solder joints at L2 and L3 so make sure your test probe breaks through that corrosion and makes a good connection - same might be said of C86/87.

You need to stop the corrosion continuing - a solution of baking soda dissolved in water and applied using a cotton bud is effective. Clean up afterwards using the IPA and clear nail varnish will work well to protect it afterwards but don't expect to easily remove it if you have to at a later date!

 

[XsamX1987]

Eeek ok so far this hasent happened "crosses fingers for first circuit board repair"

I Will do I clean up and continuity test before bed

I wont put on any nail vanish tonight

 

[kellys_eye]

I wont put on any nail vanish tonight

...and we won't tell your mates you use it.....

 

[XsamX1987]

Hahah Exactly

 

[XsamX1987]

As Its a 20+ year old computer the power supply is a AT power supply and it connects with two 6 pin connectors

I had to remove the 12pin bracket from the board and I accidently damaged it

Do you know what that part is called

I found a replacement female din easily but not the Bracket

Here is a pic I found and I have highlighted the part

 

[kellys_eye]

Maplin part number JW68Y

 

[XsamX1987]

Wow thank you so if I buy two I can just use them instead of a 12 pin bridge ?

 

[kellys_eye]

Yes - although you 'might' have to trim a little plastic off the side of one..... might. They will fit.

 

[XsamX1987]

Great thank you

 

[XsamX1987]

Any of these Buddie ?

https://www.ebay.co.uk/sch/i.html?_...nkw=Socket;+wire-board;+male;+PIN:12&_sacat=0

 

[kellys_eye]

(one of) the most critical characteristics of any connector is its 'pin pitch' - the distance between each pin.

There are none amongst the eBay list that either match for polarity (many are female whilst the one you need is male) and the closest one to the Maplin version has the wrong pin spacing (2.54mm as opposed to the required 3.96mm)

The Maplin item should be ex-stock??? You are also UK-based so if you can't find a Maplin place locally they'll do mail order no problem. Might as well get the 'right' part at whatever cost as the motherboard, should it still work, is both valuable and an excellent 'vintage' product worth keeping.

 

[XsamX1987]

Ok I understand

Big learning expericance thanks for teaching me

yes right part for the job

I've know ordered every thing

I will keep you updated

 

[XsamX1987]

And yes fingers crossed it works it is a lovely Motherboard

 

[XsamX1987]

already need help again

old picture with outlines

its odd the only place I have no continuity is L3
if you follow the red line from C86 that's where the continuity ends even if I put one end on c86 and flip the board to the posts of L3 still nothing

but if I put 1 end on the left of L3 and one to the right it reads so L3 it self is working just no continuity to any thing else on the board

 

[davenn]

its odd the only place I have no continuity is L3
if you follow the red line from C86 that's where the continuity ends even if I put one end on c86 and flip the board to the posts of L3 still nothing

but if I put 1 end on the left of L3 and one to the right it reads so L3 it self is working just no continuity to any thing else on the board

its VERY corroded around there ... I am not surprised that the tracks have been eaten away and the tracks going down from the right sides of L3 and L2 as well

around the right pins of C85, 86 and 87 .... around the pins of R29 - 34 ..... around JP3 ...... around the pins of the IC below JP3

You must clean ALL of that up and there is probably more that I cannot see

actually there is corrosion all over that area board that needs to be cleaned off. Heavens only knows how much is around the pins of the memory module sockets
The BIG IC socket below the memory module sockets is all corroded

 

[kellys_eye]

As Davenn points out, the corrosion must be stopped/removed. I'm not entirely sure but there does appear to be a break in the track just above L3 (on the left side) but only you can tell.

You need to stop the corrosion continuing - a solution of baking soda dissolved in water and applied using a cotton bud is effective.

Have you cleaned the board as per my earlier post? Get it well coated with the baking soda solution and use a tooth brush to scrub as much corrosion off as possible - rinse the soda off with fresh water, dry, then wash with IPA and leave to dry again.

If you get board powered up and there is still corrosion present it will get worse FAST.

Use a magnifying glass to trace the tracks and ensure your probe has a sharp point to break the surface crud to get a reading. You might have to desolder/resolder the more heavily corroded parts and 'pray' that corrosion hasn't got down the plated holes and broken the interlayer bonds....

 

[XsamX1987]

Sorry I said that was an old picture here is the new one

ferrite beads removed now

Baking soda went very well

but I can see where the lines are just dead

continuity check
C86 to 2 OK
1 to D OK
C87 TO 1 OK
2 TO C BAD
B TO R29 OK
A TO R31 BAD
AN NO CONTACT BETWEEN A AND C AND B AND D

memory module sockets look fine checked all around IC socket has been cleaned



So what do you guys think is it 100% dead time for the bin ?