Re: Logic board mop-up

[Tim Sweeney]

John - Thanks for the technique. A friend made a similar suggestion,  
only using a cutting wheel on a dremel tool instead of diagonal  
cutters, with the idea that it may be less likely to put stress on the  
pads that the cap is soldered to. Fortunately I've got a logic board  
from an LC-580 thats been damaged, and it has the same caps on it, so I  
can try different methods on that first.

Doug - Excellent info. Thank you. I've got a line on where to get some  
"dry" alcohol, so I'll follow your recommended cleaning procedures  
after I get the caps off.

On Dec 5, 2004, at 8:04 PM, Doug McNutt wrote:
At 18:21 -0500 12/5/04, Tim Sweeney wrote:
My first question (finally): Is it safe to mop up the electrolyte  
with alcohol and not follow up with a soap and water wash? My thought  
is that alcohol is a solvent: will it damage anything to go swabbing  
it around and on components, and leave its residue behind?
All electronic parts for printed circuit boards are specifically  
designed to be washable in either isopropyl or ethyl alcohol. It's  
been that way for decades.

Water is bad though unless care is taken to remove it and any  
dissolved salts it brought in. Alcohol is a good rinse because it  
carries off the water. But then acid residue from capacitors is more  
soluble in water than in alcohol.

Rubbing alcohol, from your drugstore, is probably bad because it is at  
least half water. You should be able to purchase dry alcohol from your  
local commercial cleaning supplier. A couple of dollars for a gallon  
is typical but they may not know what they have. It may say anhydrous.

So:
1) Wash with hot water and a small brush. (The surface mount parts  
were preheated to 130 deg C before soldering.)

2) Rinse with dry alcohol. A squirt bottle works nicely. Let it drip  
and air dry.

And: If you get to replacing capacitors I have found that they need  
not all be the same. All but a couple are really on the 5 volt line  
and can be 10 volt tantalum electrolytics. The others need the 16 volt  
rating but can be smaller capacitance so tantalums will still fit.  
I'll get around to posting the part numbers in a while.

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