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-   -   Need help to solder A1200 MotherBoard Capacitor (http://eab.abime.net/showthread.php?t=53156)

Foul 03 June 2010 21:24

Need help to solder A1200 MotherBoard Capacitor
 
I Just changed all my capacitor in my Commodore A1200 Motherboard R2.0B and one little piece of the circuit was cut out.

I need to know where to resolder the new capacitor

http://foulcap.free.fr/a1200mb1.png

http://foulcap.free.fr/1200mb2.jpg

:help

8bitbubsy 03 June 2010 21:32

You can either:
1) Trace it and find a bigger and healthy pad to solder on
2) Use a needle and scratch the hole a little (so the solder will stick), add flux, add solder, then put the cap back on and try to make the solder from the pad go to the little hole and stick there (not easy, I think)
3) Put a thin wire (e.g. Kynar) inside the little hole you see, and use some flux to let the solder stick (PS: Not sure if a kynar wire can hold all the power! You might do 2) instead)
4) Go to the underside of the motherboard, get a knife tool and gently cut of the protection layer of the trace that goes up to the hole, then add flux and solder a long wire on it and wrap it around the corner and up to the capacitor =)

Eeek, what is all that red stuff? I'd remove that instantly :o

Foul 03 June 2010 21:34

yes but i don't know if the hole is the original solder point ... or elsewere :\

8bitbubsy 03 June 2010 21:36

Quote:

Originally Posted by Foul (Post 674776)
yes but i don't know if the hole is the original solder point ... or elsewere :\

The pad had a little trace that lead to the hole. Yes, it is the original trace.

Foul 03 June 2010 21:38

soldering .. and testing ...

Call Firemen ... :D

Foul 03 June 2010 22:07

Booting .. Everything fine !

Thank you :great

8bitbubsy 03 June 2010 23:28

You should try to beep it with a multimeter to make sure there is good contact. It might boot without it, so have that in mind.
One multimeter pin at the cap's pad, and another at the underside of the mobo (where the hole is)

Loedown 04 June 2010 00:07

If the red silicon like substance is your work, not a good idea, SMD caps will stay in place just fine. The reason some manufacturers use silicon to hold larger style capacitors in place is to avoid vibration causing stress on the component's soldering, such as in power supplies, absolutely no need for it on a motherboard and it's always a bastard to get off later.

In the picture you showed of the lifted pad, the hole to the right is called a via, which is a point between one or more layers on the PCB, it will have a corresponding hole on the underside of the board which you can use to trace where the via goes. If that had been me repairing it, I would have fashioned a pad for the capacitor using mod wire, forming it in the shape of a series of repeating "U" or sine wave shape if that makes sense, using a small dab of nail varnish to hold the wire in place, allowing that to dry and then soldering the wire in the via, top and bottom, then soldering the capacitor. As the wire length is short, when you solder the capacitor down, it will re-melt the wire enough to melt the solder in the via, but it will harden again and form a strong mechanical bond.

Foul 04 June 2010 00:31

Quote:

Originally Posted by 8bitbubsy (Post 674794)
You should try to beep it with a multimeter to make sure there is good contact. It might boot without it, so have that in mind.
One multimeter pin at the cap's pad, and another at the underside of the mobo (where the hole is)

Every capacitor replaced was tested with a multimeter ;) it's not my first attempt to repair PCB, i'm administrator of www.jamma.fr, a site concerning jamma Boards ... got plenty of them .. and repairing them in my spare time ;)

The red substance is in fact hot glue ... just because some cap are moving .. not much ... much i don't like that ... so a little hot glue between motherboard and cap and nothing move... and just for information .. there is a slim dvd-rom drive just above this caps .. so there are some minimal vibrations .. not much but there are ;)

Loedown 04 June 2010 07:22

I personally wouldn't have used the hot glue, but at least it's much easier to get off as opposed to silicon.


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