Re: Desoldering Apple IIc RAM chips

[a2aviator@gmail.com]

De-soldering components from //e and //c motherboards, particularly
the pale green ones, is just a major pain. Statistically it's got way
worse rates than similar actions on other PCBs.

The component insertion is typically blamed but it's no different than
the average assembly. My opinion on it is that Apple's Singapore
production facility used methods and products that produced a lousy
product with regard to serviceability. The via's and thru-hole plating
just is not as good as it could be.

Lets put it this way, if I'm marooned on the ISS and that RAM chip
replacement is the only way home, I'm more inclined to snip the leads
from the top and remove it that way because I can use the heat and
thwap method to get it out, or similarly, that it would be the key to
repairing the USS Minnow.

I have had better than average soldering equipment, and myself have
much fewer problems due to being aware of the weaknesses when
repairing Apple PCBs.

Using a de-soldering continuous flow suction handle is the most
efficient way to go, just not available to most everyone. Once flowing
solder has been verified from both sides of the PCB, place the tip
right down to the PCB with as little pressure as possible, just enough
to make contact, and push the suction button. Half a second and move
it around leaving the IC lead touching the tip so as to move the lead
around in the hole. You'll remove nearly all the solder at this
point.

When you have done this to all the leads, hold the board up to light
and see that you have light through each hole. After that, using an IC
plier type tool, one that works from the long side of the package, not
the U shaped thing that comes free with stuff, and use that to rock
the IC back and forth a little and it will break free of the remaining
small solder amounts.

Some examples of tools are;

http://www.excelta.com/marketplace/browse.asp?category=310

These are not cheap, but you get the idea.

Thats not to say you can't do it without, but if you're going to work
on them frequently, it's not a bad investment.  There are of course
far-east knock off varieties of these tools. As long as they are
precision enough to work with 600 and 300 mil packages, no harm is
done. You can use the 28 pin one on the 40 pin package, just move it
around, where as you may not be able to use the 40 pin one on a 28 pin
package due to surrounding components, so if you want to get just one,
the smaller one can suffice.

The 40 pin 65C02 DIP package is 600 mil and the 4164 RAM chips are 300
mil, as reference points.

You'd be hard pressed to find a 400 mil IC package on an Apple PCB
that is generally through-hole construction. This refers to the
general design of the PCB, and encompasses nearly every Apple II
and /// product ever made, even the IIgs with all the SMT (Surface
Mount Technology) is still considered to be through-hole. Partially
because there are still such components on it's PCB.