[plug] hot freeze - not a contradiction in terms

[Brad Campbell]

Gavin Chester wrote:
>>
>> Faulty caps are easily spotted (a bulging or a browny colour on the top
>> of the cap can) and apparently easy enough to replace but I have yet to
>> repair a motherboard myself.
> 
> Ewwwhh!  Hopefully that's an absolute worst, worst case scenario that
> rarely happens :-(

Unfortunately not as rare as you might think. I've had to repair a number of boards due to faulty 
caps. The worst of which was an old Soyo 5-EAS board (which HAD to be repaired as it was in an old 
DOLCH luggable and nothing else would fit). As the caps dried out the extra ripple in the supply 
caused a couple of them to start to go resistive, this placed an extra load on the supply which 
cooked two of the inductors in the CPU regulator SMPS, which then resulted in a blown switching FET. 
Unfortunately as this happened over a prolonged period the extra heat caused some extra collateral 
damage nearby on the board and the extra load on the PSU and resulting heat dried out several caps 
in there as well.

All in all the repair time was probably 20 hours and about $300 worth of new caps and other semi's. 
However, it all came up good in the end and is working like a champ today (the repair would have 
been 4 or 5 years ago now).

If you are going to do it, you need a good desoldering station, and make sure you use the highest 
temperature rating and lowest ESR caps you can find. (I got mine at RS and they cost a fortune, but 
they have been hammered since and are still like new)

(I had a recent model Gigabyte board die due to this last year and in the process the extra load 
cooked the PSU connector on the motherboard and PSU - I threw it in the bin and bought a new one)

Brad
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