|Hello Paul, one other VERY important|
Message #20 Posted by Norm on 5 June 2003, 1:45 p.m.,
in response to message #16 by Paul Brogger
> Norm, I suspect no single person has done more to increase demand for the 34c than has you.
Yeah, now I am losing all the auctions and can't afford one !! Oh well, its not good to keep a fine thing all to yourself, and in the end, I can't own ALL of them
If you guys are chasing after them now, in your later years, you still can't have the total fun of getting one brand-new back in 1980, for high school calculus. That was really 7th heaven. Gotta feel sorry for all the public school kids nowadays who will never learn to even add 2+3 .
As to how to bring a solderless unit back to fullest performance (if the connections go intermittent) I dont have
all the answers there, only some of the problems.
I tried cleaning up one by soldering it with a controlled temperature precision iron
Firstly, the pins themselves build up a blue oxide,
esp. on the 3 small memory chips.
So they weren't accepting solder.
The only way to fix that was flip the chip on
its backside, and rub it for awhile with the iron.
Secondly, even with the lowest controlled temperature,
there was tendency to melt the plastic underneath the
Thirdly, you can never undo this type of work, so if a chip blows you can't replace it and the supply of parts rapidly dwindles.
I would favor the Luiz approach....... pull it apart and clean up the contact surfaces with a cleaner. Then use some type of light-oil that would keep the surfaces more corrosion resistant (dont know what oil).
The chips themselves, well, flip them upside down, and look for cleanliness of each pin. Probably a bit of scraping with a jewelers screwdriver is all that's needed. I think Luiz was using a bit of emery paper, which might be OK if
followed by a squirt of aerosol degreaser.
A low-power stereozoom microscope is just dynamite for this.
You can see exactly what's going on with each pin.
I have one...... although they are $800 new, it can be such a fine tool that I say its totally worth the money.
THE LAST THING is ESD. I dont think you stand a snowballs chance in Hell of being able to clean up all the pins on an ancient CMOS chip without frying it. The only
way this will work is if you ground yourself out, ground
the jewelers screwdriver out, and work on a piece of anti-static plastic or even a piece of aluminum foil
while you work each pin of a chip on its backside.
Anyway, clean all these boundaries where the contacts are occurring, a bit of oil on everything, put it back together and cross your fingers.
That's the Luiz approach, and its better than what I tried,
or, the thing about 'painting' that you were describing.
Do recommend lubrication of the switches, or they will grind flakey bits of metal where the contacts are sliding.
And these are antiques that there's no turning back
(unless this whole country gets more traditional in its thinking, from the boardroom on down). So we really need to
cherish these items. I think we can take a line from the antique radio crowd...... "you are dealing with a nostalgic item that goes beyond just your personal ownership. Later it will be owned by another person. Do any work so that it will last and ould please the future owners also".
Still recommend "Tri Flow" for slide switches (from the black aerosol can, shake well, but only one drop of the liquid onto a Q-tip and then rub it onto there.)
HEY one OTHER VERY IMPORTANT IDEA about SPICE calculators
(dont think people have bought into this yet, but Luiz is starting to). Starting with the extraordinarily difficult case-halves, and continuing with the inner plastic clips that retain the electronics module, this plastic was mis-designed and you have to bend it TOO MUCH to get the plastic ratchets to spring away.
In these situations, get out a fresh X-Acto blade, and trim away just .010 or .020 of that plastic. Do it manually.
THEN, the ratchet action comes apart easier, for future service.
If we don't get into doing some of that, the clips will simply break off in future servicings. I know because I'm already seeing bust-offs of these clips inside.
Try it sometime and you will be well-pleased.