Re: smd precision resistor "paint layer" peeled off while soldering *** advice needed ***


Chuck Harris
 

As long as you cleaned the board of all of the corrosive (to copper)
residue, any solvent based paint would be fine. This is just a slow
computer, and as such it is all either dc or digital.

Also, look at the solder joints on the 4 capacitors. They should be
shiny as a mirror. If they are milky, or white, the capacitors have
not been replaced. If you touch one of the capacitor's solder joints
with the tip of a soldering iron, and you get the stench of boiled
radiator and rotten fish, there is electrolyte present.

-Chuck Harris

Rogerio O wrote:

Dear all,
I was doing a A5 board repair of a Tek2465BCT I bought some time ago.
This is a late unit, serial # B0577746 and the A5 board is the 671-0965-05.
I inspected the board when I bought the unit and there were no signs of corrosion, so I left it as received for quite a long time.
It seems the caps have been replaced ( I can't say for sure) but the board was not cleaned well enough so the corrosion started.

Near the ADC (U2101) the only pads "missing" are the ones for C2520, but I had to remover and solder again some SMD components in this area.
While doing this the "paint layer" of R2012 (RES,FXD,FILM:10KOHM,0.1%,0.125W,TC=T9) fell off, exposing the tiny traces.

I could not find a direct replacement for it so I am thinking of leaving it there and apply a layer of some isolating material (PCB varnish, for example).

My question is: Is it possible the the varnish would react with the exposed traces, changing the component characteristics?

|Is it better leave the component as it is? Any other coating material suggested?

Thank you in advance,
Roger






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