On 23/11/2014 13:59, N_Cook wrote:
Mackie ProFX12 , a couple of years old. OK at soundcheck, but failed in
first use proper. Owner retained one XLR feed and used a 1/4 inch line
for the other channel and continued.
With me checks out fine. Now the double XLR boards has that style of
soldering , pin and cup?, where the end of the pin is enveloped in
solder. Then as 4 closely spaced pins for the XLR difficult to check by
flexing. Will try tomorrow with proper continuity check on all pins.
I've seen this failure before , but I don't think with proper solder.
Does PbF expand on cooling and so the cup helps to break contact, more
than just a ring of solder, or just cold-solder joint failuredue to
thick + long pins so substantial heatsinking.
At the moment no sign of any solder sweated thru the presumably plated
holes to the component side of the pcb, "nice" clean gold finish,
suggestive of inadequate heating at soldering.
Hopefully a pbf problem on that rear board and not balanced line feed
buffer amp failure , requires removing all the top panel hardware.

a pic of the "pin and cups"
http://www.diverse.4mg.com/mackie_pbf.jpg