Re: Diagnosing a C64 problem

On Jun 3, 2:32 am, "Ed" <nos...@xxxxxxxxxxx> wrote:
"Miika Seppänen" <m.seppanenNOSPAMH...@xxxxxxxxxx> wrote in messagenews:8pu744ho48t2gkajorf166qfkp4ql6bee9@xxxxxxxxxx
...
When replacing chips, ALWAYS install a socket, preferably a better
quality one (not the cheaper spring types usually factory-installed in
C='s.)

For anyone contemplating this, here are a few tips.

A "good" socket is of little advantage if one hasn't removed all
the solder and cleaned the flux off the formerly soldered chip.

Failing to clean the chip pins after desoldering can result in
poor socket contact, IC pin or socket damage.

Use "soder-wick" or similar desoldering braid to remove
the solder dags left on the IC pins. Then clean the pins with
a solvent e.g. lacquer paint thinner.

Don't let the cleaning fluid get into your socket lest it dissolve
the plastic or flux and a leave a film on the contacts.

Do all that and a "normal" IC socket will be just fine. I actually
prefer standard IC sockets over the "turned pin" variety. The
pins on the latter break easily and can be a pain to remove.
Just make sure your standard socket is of the "dual wipe" type
i.e. makes contact on both sides of the chip pins.

BTW if one ever needs to remove a socket and don't have the
professional tools, it's best to carefully cut it up and remove
pin by pin.




Also remember that when desoldering, I found the following method
to be indispensable.



First, I turn the board over and expose the pins from the bottom
that need to be removed.

Then I touch the solder braid sideways on the pin that I am trying
to remove and then touch the doldering iron on top between the braid
and the pin at a 45 degree angle for about 3-4 100's of a second
(NOTE: if -placed too long damage to the board is IMMANENT).

Then repeat the same procedure exactly as mentioned to all the rest
of the pins on each row of all the chips that you desire to remove
until all show signs of light exposure through each hole when held up
to light.

Sounds simple, right? However, just doing this still damaged some of
my circuit boards (unfortunately), even though the holes were PERFECT.
So I made another discovery.

After removing all the solder from all the pins, touch the soldering
iron to each pin just long enough to "PUSH" it over near the center of
the hole to remove any excess solder that's still connecting the pin
to the board.

Do this to each pin until sunlight and centering can be seen
through the "TOP" of the board when held to direct sunlight ( or a
lamp if it's night time or dark).

Then finally, I analyze each pin from the TOP of the board and check
to see if there's any excess solder touching any of the pins which
could result in damage when being removed.

If I find any pins that have solder on them, I break out my wick
again and hold it sideways to the pin, touch my iron at a 45 degree
angle (repeating the first steps again) until all pins are TOTALLY
FREE OF ALL SOLDER ON BOTH SIDES!

Then the chip should be so easy to remove that most will just "fall
out" when turning the board over! Some, will still require a mini
flathead screwdriver, or a chip remover tool to pull "up" on it to
remove it, but it still should come out fairly easy at this point.

I realize that this doesn't sound like a statement from a "GENIUS,"
but it IS FACT, and I have been using this method for quite some time
with amazing results!

I just hope that sharing this technique with someone can help them
in some way......


Good luck!


Charles> 8-Bit Designs

http://www.8bitdesigns.ath.cx
.

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