On 02/10/2014 03:24, David Platt wrote:
However, some example are so badly fouled the only way I have found to clean them properly is to submerge the PCB and heatsink assemblies in
hot water and detergent and scrub them just like dinner plates and saucepans. In order to thoroughly dry the PCBs, I have used an oven set to
low temp, hot air from a room heater or gun and simply the sun on a warm day.

This is obviously a very time consuming process requiring a lot of disassembly and reassembly, cleaning the fans themselves is one of the most
tedious parts.

Recently I had to clean a couple of Crown XS700s that were completely fouled with black fluff that proved to be electrically conductive !!

Turns out they had been in the same rack with another amplifier that went up in smoke, filling them with carbonised fibreglass soot. This took
more than the usual amount of time and care since a 2kW SMPS is built on the same PCB.

Anyone know an easier way or have useful comments?

I suppose it depends on what sort of materials are on the pcb's etc but
I would be trying some suitable solvent like acetone or white spirit.
More costly but probably less time involved. It would need some capital
expenditure for a cleaning bay too.

I wouldn't ever use acetone for that purpose... it's too hard on too
many plastics.

Bob Pease used to swear by the practice of putting PC boards into his
dishwasher, with "a full load of Calgonite" detergent (it's not full
of chlorine-based disinfectants), running them through the normal wash
and rinse cycle, and then drying. He swore that this was capable of
getting PC-board leakage down to levels below those that an expensive
"professional" solvent-based PC-board cleaning would deliver.

A manual rinse with deionized water before drying probably wouldn't be
a bad idea, if your local water is at all "hard".

I've heard of people using this approach on complete pieces of
equipment (after doing enough of a partial strip-down to remove
anything made of paper or cardboard) with some success. Depending on
how vigorously your dishwasher "sprays", it may be as effective at
removing build-up crud as a manual scrub would be.






Only military grade ICs are specced to hermetic sealed packages. For all
else, water is likely to migrate to the die with some probability
greater than zero, only needs going along one pin of one IC. Once water
is in there , how to expel, without leaving any trace? Is dry heating
all to 100 deg C, going to do that?