Re: HP11C emulators?

krw <krw@xxxxxxxxxxx> hath wroth:

Ever repaired an HP45's power switch? Mine is quite touchy after
thirty years sitting in a drawer.

Sure. What's probably happened is that the grease that lubes the
slide switch has turned to tar and is not making contact. You can
sometimes get away with just applying some mild solvent (alcohol) to
the switch, slide it back and forth, and sorta smear the grease
around.

However, if you've been moving the switch back and forth zillions of
times, then you've probably worn a grove in the gold contacts on the
circuit board. That will require disassembly.
<http://www.hpmuseum.org/disasm.htm>
Try not to wreck the stick on label when you peel back the corners. I
use a hot air gun to soften the glue (and hopefully not melt the
plastic case).

I've been fixing switch contact pads with gold leaf and very tiny wire
(available at art supply and hobby shops) which are a real nightmare
to use. The stuff sticks to everything and won't release. For
practice, try cutting and applying a single layer of toilet paper
without ripping it apart. Good luck.

If it's really been sitting for 30 years in a drawer, the NiCad
batteries are dead, leaking, rotted, corroded, and disgusting. Don't
try to charge it if the batteries are swollen or covered with white
crud. They're ordinary 850ma-hr NiCad batteries and the battery pack
can easily be rebuilt.
<http://www.cs.uiowa.edu/~jones/hp/battery/>

If there's corrosion damage and white crud on the inside, just clean
it off with water and some mild solvent such as alcohol. Don't get
anything near the keyboard or capillary action will suck in the
liquids. Blow away the excess water, let air dry for a day, and you
have a chance.

Also, check the shorting bar inside the charger connector, which has
the bad habit of becoming intermittent. It may not be a bad on-off
switch but a flaky shorting bar. Just clean the round pins around the
shorting bar.

HP45 Crystal modification:
<http://www.hpmuseum.org/45crys.htm>
<http://www.decodesystems.com/hp45-stopwatch.html>

Drivel: Ancient photos of an HP65 rebuild.
<http://802.11junk.com/jeffl/pics/hp-calc/index.html>

--
Jeff Liebermann jeffl@xxxxxxxxxx
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
.

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