33E repair



#8

I have a 33E in which the badly corroded battery contacts have finally broken off. Any suggestions on how I might repair it?


#9

I wasn't able to find an enlightening photo (but http://www.hpmuseum.org/tech30.htm has several that are suggestive). However, would this be a candidate for an allegator clip solution, to an external battery pack (or even AC adaptor)? As regards a collector's item, it would look really ugly, but as regards a working calculator, it might have decades of life left.

#10

Hi;

Once (not upon a time, instead a long time ago) I replaced an HP34C's corroded, broken contacts with small springs found in many battery compartments. I remmanaged the spring tips in a way I could also replace the metal rivets too. The only matter is the distance, you should check how much of the spring is necessary for good contact and not much pressure, what could bend (deform) the springs.

Unfortunately, the calculator must be opened. At least, I do not know any other way to do what I did with the calculator closed. And opening a Spice requires technique and... patience. Lots of patience.

Success.

#11

To replace the battery contacts, the metal clips (used as the ESD purposes) stolen from the computer's cabinets will do.
Have to re-solder or re-screw the clips to the small board and rerun the battery wires back to the power supply inside of the calculator.
You have to open the calculator though.
HTH,
Pyerre

#12

You can make some replacement clips out of springy berrylium-copper alloy strip available at Small Parts, Inc. Attach them with small (#0 or #1) screws or even better small rivets.

I think you will also find that the corrosion has gotten past the little battery contact board and damaged the flex circuit that connects it to the main power board. You will need to use small stranded wire to reconnect it... a task not for the unskilled solderers out there.


#13

Here's an old thread where I describe how I fix these:

http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv007.cgi?read=14438


#14

I had taken a similar, but cruder, approach to Katie's when repairing the battery terminals of one of my "old" units. I bought the thinnest strip of brass I could find from a hobby shop, cut it into the approximate size and shape of a terminal, bent it to form a contact, punched a hole in the upper part large enough to surround the rivet, filed the backside down, then soldered it to the broken terminal.

A soldering iron will heat the board and strip quickly, but they seem to be able to take it.

The repair worked, but the metal strip was too thick (20 mil?); it doesn't give.

I now have a "new" unit that needs both terminals repaired. For that job, I then got pieces of "shim stock" from a machine shop. It's available in brass or steel in various thciknesses from 3 mil to 15+ mil. (Katie recommended 0.01" = 10 mil).


BTW, I discovered and use a good, safe, and easy way to separate the case halves of Spice units. I'll dig up the link where I described the method. Sometime, I'll prepare the description with pictures I took.


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