Archive of the former Yahoo!Groups mailing list: MOTM

∗∗DISCLAIMER: this is not indended for any 1, 2 or number of people
specifically. ∗∗

The following tips are based on 1 year of MOTM soldering/failure issues

a) Parts in backwards

PLEASE resist the urge to power-up a module ∗before∗ checking every IC for
being
in backwards. They don't like it. I take great pains in the pcb layout so
that they all point
in the same direction. If you are not sure, just call or email.

Also: twisted pair wiring backwards. Double-check that wires to the jacks
are correct,
not swiched. If it's soldered to the ground plane on the board, it had
better be soldered to the
ground lug of the jack.

b) amount of solder to use

I hope to get some example shots on the web, but before that:

1) generally speaking, you ∗do not∗ ever need to apply solder to the top
(component)
side. Except on the top-side ground plane connections, where it is hard to
occur, applying
the solder to the bottom side will flow up and around the top of the lead.
DO NOT add solder
to resistors, diodes, etc from the top side! There should be no "blobs" or
"mounds" of top-side
solder on the leads. There should be just a "wisp" of solder to smoothly
cover the pad surface.
about 1/3rd - 1/4th of the amount the bottom side has.

2) On the bottom: we are NOT going for the "Hershery Kiss" look. Rather, a
moderate-sized, evenly
distributed and flowing around the lead. The "BB pellet" look is bad, too!

c) you MUST wash off the organic flux!

I have seen some ...errr...."interesting" things happen when the organic
flux is left on (no, it
doesn't eat a gaping hole). Rather, you get large (I mean LARGE) DC offset
voltages. One board
had 2 volts of DC offset on the FM 1 jack!! Turns out, the op amp had the
organic flux on every
pin and this caused leakage currents to flow into a 1M resistor (that's 2ua!
Zowie!). BE SURE
the board is washed.

Now, what happens if ∗all∗ components are in, and you have to replace
something. Use the no-clean.

d) Do not use the lead clipper as a lawnmower

I have seen more than one instance where the leads have been trimmed almost
flush with the pcb.
THIS IS NOT GOOD, What you want is to NOT CUT INTO THE SOLDER, just trim the
lead.
DO NOT trim IC pin leads: they are OK.

Conversely, I have seen several "forgotten" leads left untrimmed, causing
intermittant (sp?) shorts.

e) it's ∗OK∗ to trim the wires in the kit to suit

I use "generic" wire lengths to cover most cases in the kits. But sometimes
the wire is too long. So,
if you feel that taking a 1/2" off would be better, OK!!

Again, I'm not picking on anybody. Just trying to address some assembly
issues. Nothing beats a good visual
inspection before power-up!

Paul S.