HP32E Repairing

[ElectroDuende]

(10-11-2015 11:03 PM)ElectroDuende Wrote:  Hi guys,

A couple of days ago I got a really nice (at least externally) HP32e unit, made in Singapore in 1979. It didn't work; in fact, one of the battery tabs was broken, and there were signs of corrosion on the battery PCB.

I opened it in seconds, with almost no effort, using the technique described here:

http://www.voidware.com/calcs/spicerepair.htm

And this is what I found inside...

[...]

As you can see the leaked battery electrolyte has completely destroyed the flex cable from the batteries, and is already attacking the flex cable that links the power board and main board. I'll cut out the damaged part and replace it by a segment of flat cable taken from an old HDD bus.

Fortunately the LED display and power board are free of corrosion (that white spot on power board has not gone under the protective layer, and the blue spots on the leftmost LED are actually on the surface of the lens, out of the "danger zone"). Main flex PCB is also in very good shape:

[...]

Something that surprises me is that I've read in several threads of this forum that HP32E lacks the central small IC, and my unit has them all... any explanation for this?

[...]

There is one missing pin in that IC, but it seems to be normal in other members of Spice series...

I hope I can come back here tomorrow with good news!

Unfortunately the repair was not successful... or, at least, not completely.

It was quite easy to clean all the blue dirt from the battery PCB and to solder a flat cable from there to the power board... but I'm afraid that the LED display has a fault. And considering how it is driven, it is not a falt due to contacts but to the LED module itself.





As you can see, the top segment of second digit, and half of both segments close to it don't ligth. This makes it impossible to tell apart 1 and 7, rendering calculator mostly unusable.

I see that the LED substrate itself is glued to the base and soldered with thin wires... basically impossible to replace but with another complete display. I'll try to locate a donor, but I'm afraid that any calculator, bad enough to be a donor, will probably have a display in worse conditions... :-(