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N3FIX > TECH 29.11.18 04:53l 43 Lines 1939 Bytes #999 (0) @ WW
BID : 399_N3FIX
Read: GUEST
Subj: Surface Mount repair - Lead Cut Method
Path: IW8PGT<CX2SA<N3HYM<KA3BVJ<N3DWB<N3FIX
Sent: 181129/0244Z 399@N3FIX.#EPA.PA.USA.NOAM LinBPQ6.0.17
Surface Mount repair - Lead Cut Method
The subject is a USB to CAT CI-V interface cable. Someone (not me)
plugged it into the wrong 3.5mm port and blew the chip up so badly that
the case was deformed due to the heat. The chip was obviously bad,
there are very few other chips on the board, so I just ordered a new chip.
Some folks don't have a hot-air desoldering tool for surface mount
components. So how does your average Plugger of ham get a multi-pin
surface mount chip off the board without damaging the board? When you
know you have a ready replacement chip there's an easy way to remove it
from the board. Don't try to unsolder every lead and try to preserve
the chip. You will get frustrated. Just clip the leads off with your
best fine clipping tool or EXACTO knife. Tip the chip up and clip the
remaining leads.
I have a simple general use soldering iron as well, it gets a LOT of
use. I don't file my tip down. I take it out anneal it in a and hammer
it down to a fine point on the anvil. The act of hammering it to a
point makes the tip hard again. I find it lasts a lot longer this way.
You will need a sharp tip on your iron to do this properly.
This is what makes it easy, just take the hot soldering tip and wipe it
across the lands of the board. The clipped off leads will stick to the
iron and they will just be left behind when you dip the iron's tip in
the cleaning sponge. Easy!
Once the chip is off then using a set of helping hands and magnifying
glass, putting the new chip in place is simple (provided your hands are
steady and your eyesight is good). The lands should be clean and only a
tiny amount of solder is required to make the connection.
None of us are getting any younger, so using a eye loop and a magnifying
glass in conjunction can be helpful too.
Hope you find these tech tips helpful.
de N3FIX at the Cly Institute for Radio Repair.
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