On 6/21/20 10:41 AM, Jon Elson wrote:
On 06/20/2020 09:41 PM, Charles wrote:
On 6/20/20 8:31 PM, Jon Elson wrote:
I confirmed the bad one by removing the piggyback and the failure
returned. Now I need to desolder the bad one without ruining the
board. I may just cut the leads off close to the bad chip, and
solder the replacement to the stumps. (Normally I remove the legs
and install a machine-pin DIP socket). Or just solder the piggyback
and leave it there... thoughts?
Cut the leads close to the body. Apply a soldering iron to each
lead, and pull the lead out with tweezers,
simultaneously heating and pulling. This is very gentle to the
board, just doing one at a time. Then, you can vacuum out the holes
and install a new chip or socket.
I've done this many times, and never wrecked a board.
Jon
That's how I do it... the vacuuming is the problem. Someday I need to
get a good vacuum desoldering station. Right now I just have a
spring-loaded solder sucker (which I can do a pretty decent job with
on most boards). But this high-density layout (2 traces between DIP
pads) I'm a bit wary of.
Just be gentle, and you should be able to do it. Also, in some cases,
you might heat from the opposite side from the solder sucker. That
way, you can keep the soldering iron on the pad until you have
triggered the sucker. But, yes, the hollow soldering iron with
powered vacuum is amazing the first time you try it. I got one at an
auction years ago, it is much better than the regular iron and
plunger-sucker.
Jon
The small company I first worked for had a Pace unit. I remember not
being impressed with it - frequent clogs, pads lifting, and not getting
all the solder out, no matter how we set things. Still beat solder-wick
though!
I got it done, but pin 16 (which connects directly to the internal-layer
ground plane) was a bear. From the feel of it and the heat required, the
draftsman didn't bother to make pad reliefs. Anyway it's now socketed,
so of course it will never fail again!
I also made a small jumper on a 15-pin D-sub to connect Monitor Present
L to ground, so that annoying "Monitor Error 9" message stops ;) On to
the next project!
