On Friday, December 16, 2016 at 12:07:12 PM UTC-5, N_Cook wrote:
Third time in as many months, usual PbF phantom problems, solder looks
fine but no wetting between eyelet and pin and grey (tinpest?) pin, even
after desoldring.

I will render an opinion here based on my experiences with conventional lead-containing solder of differing natures.

a) Non-Eutectic solders will solidify in a non-linear fashion as it cools.
b) My experience with 60/40 and 50/50 solders with wires is that the cooling is often based on the wire as it is a heat-sink.
c) Dynaco equipment uses a lot of eyelets set in circuit boards.
d) Using solders as described above, on more than one occasion I have gotten visually excellent connections that simply twirl in the eyelet, as the solder cooled (dumped heat into the wire) so fast that the shrinkage pulled it away from the eyelet before it was actually solid.

This is purely anecdotal.

Today, I use only truly eutectic solders on my electronics (37/63 lead/tin) - with a very few exceptions, when for one reason or another I need to use silver bearing solder. In those cases, I use 96/4 tin/silver, and great care not to move anything as it cools.

Peter Wieck
Melrose Park, PA