Friday, 30 August 2013

PCB repaired....

... Well, I think it's repaired!

Last night I started the repairs to the PCB, and everything went very well indeed.

I used Electrolube Silver Conductive Paint to repair the broken PCB track.  I've never done this before, but after the paint dried - a quick test with the multi-meter told me I have continuity, but lots of resistance.  I used a very fine modelling brush to apply the paint, and this is what it looked like after that first coat:

I was pleased with the results.  If you click on the picture to view full size, you can actually see where the cuts had been made with a knife, and the paint has ran into these crevasses.

This morning, still not being happy with the multimeter readings, I decided that when I get home tonight to apply a second coat, and everything will be fine...   And so that I did....

But disaster soon followed......

This time, used masking tape and mask off the areas not to be painted, and guess what happened... the conductive paint ran straight into those crevasses, under the masking tape to make the best possible electrical connection with every track next door!!!    I can tell ya, blue language was to be heard for miles!!!

Luckily, I had pulled the tape back in good time to see how things was looking when this was drying - I quickly grabbed a bottle of Meth Spirits and wiped off the excess... what a bloody mess.... I lost a number of Heart Beats during all this.  I was making continuity with the surrounding tracks, which is the last thing I possible wanted!

Rather embarrassingly, after cleaning  - this is what the board looked like:

As it would turn out....  According to my multimeter readings I'm not dropping any resistance now -  look at the width of the track repair, that's probably the reason why!   Might not look elegant, but I think she'll hold captain...  And, if not, I'm cutting the bloody track away myself!

I think moral of this story - try on a scrap circuit board first, otherwise the circuit board might have to be scrapped!

More successfully however was bonding the heat sinks back onto the power MOSFETs that previously came loose...  I used a good quality silicone adhesive with excellent thermal sealing properties :

Just need to get this lot back into the base, and that hopefully completes this part of the electronics....