Acid Core Solder

[Richard H. Arland]

Yesterday a box arrived from California with a Knightkit VTVM that I had
purchased. It was packed poorly, and rattled when I lifted it out of the
box. I immediately opened it up and found that the C-battery had come
lose in shipment and had rolled around inside the VTVM during transit.

Nothing appeared to be broken or mangled, however, there was a peculiar
whitish coating on all the mild steel hardware. Apparently the unit had
some stainless steel nuts and lock washers which were not affected, but
all the mild steel inside the VTVM had this weird whitish coating. The
coating would rub off slightly when touched.

At first I thought that this might be leakage from the PEP-Boys battery
that had come lose inside. However, the battery didn't look like it had
leaked at all. The unit fired up and I could Zero out the DC scales but
on Ohms and AC, the meter had a mind of its own. First it looked like it
settled down then it would jump full scale and pin the needle on the
right had side of the movement (on AC), in Ohms, the opposite was true,
it would deflect full scale then abruptly the meter would move to full
left deflection, stopping at the pin on the meter movement.

I looked over the solder.....whoever built it used WAY too much solder.
I tried cleaning up a couple of suspicious connections by wicking the
solder off and resoldering. However, even after cleaning up the pads on
the PC board, the solder didn't really want to hold on the traces. There
was an unusual pitting around the PC holes in the area of where the
wires entered the board and solder was applied. I tried using a very
small wire brush on these connections with only limited results. The
solder just didn't want to adhere to the PC traces.

In almost 40 years of building kits and playing the BA restoral game, I
have never come across this particular phenomenon. I am thinking that
this meter may have been constructed using acid core solder. Anyone out
there in BA land ever encountered something similar to this: whitish
power residue and the inability to resolder PC pads?

73 Rich K7SZ

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