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Lead-free only? failure mode ?

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.

Reply to
N_Cook
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Lead-free solder does not flex. It fractures. Lead based solder will flex because of the lead.

Paul

Reply to
Paul Drahn

a pic of the "pin and cups"

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Reply to
N_Cook

I wonder if there is a significance to the sharp deliniation between the mirror finish of the cup part and the maculate finish of the sleeve part. Indicative of differential cold-shocking while cooling ?

Reply to
N_Cook

** The term "lead free" incudes a huge variety of solders nearly all of which are quite flexible.

As wire from a reel, 99C (tin/copper) solder differs little from 60/40 in terms of flexibility.

** Strange how cracked solder joints on PCBs long predatse the use of Pb free solders.

IME - the main reason for bad joints with Pb free solders is failure of the base metal to alloy with the solder - partly due to the use of almost pure tin and partly to do with the use of low activity, water soluble fluxes.

... Phil

Reply to
Phil Allison

no bypass contacts on insert mode. They've skimped on having no MUTE reminder LEDs per channel and one under the bargraph that mutes the whole lot, unLEDed, just where you would unknowingly push it on handling the mixer, 10 minutes wasted there

Reply to
N_Cook

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