On Wed, 16 Mar 2016 20:51:46 -0500, Jon Elson wrote:

Cursitor Doom wrote:

On Wed, 16 Mar 2016 11:45:04 -0700, DaveC wrote:

€œchecked out fine...€� means you tested what? Capacitance? ESR?
In-circuit? Removed?

Visually?

No signs of bulging or seepage.

I was just taking a closer look at the board a moment ago under a glass
and spotted something that requires further investigation. Going to
have to get my stereoscope out of storage for this one. Tiny clusters
of what look like *very* fine gauge enamel copper wire clearly bridging
across vias in various points around the board and obviously not
*supposed* to be there.
Woo Hoo! Sounds like tin whiskers! The conformal coat is "SUPPOSED" to
suppress the whisker growth, but there are quite a few reports that the
whiskers just poke through the coating, they ARE real sharp.

Jon

Thank you, Jon. An interesting suggestion! But I was under the impression
that:

1. TW growth happened solely inside chips and so was normally invisible.

2. tin whiskers were invariably silver in colour.

These I have here are like the old kind of enamel copper wire. Nowadays
all enamel copper seems to be clear, but back in the day the enamel was a
sort of deep plum shade - which is what I see here. I'll do some searches
for pictures of TW and see if some match what I see on this board....