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I just got two new calculators, and would appreciate your help.

1. 28S - Left keyboard has a full row and a full column of non-working keys. I don't have any idea on how to open the case, and web search did not produce any information. I am clueless. The calculator is in great shape, so I would like to keep its appearance, and fix it too (sort of eating the cake and keeping it...).


2. 33E - Old hardware version (no soldering on chips). Topmost small chip is missing pin number 8. My ideas are: a- cannibalize a for parts machine - i don't have one, so ....
b- recreate the pin - not so easy, as nothing is left from the original pin.

Any ideas ? I can probably fix it myself, but I am certain that this forum will help me do it the best way.

Greetings from Brazil.

About the 33E -

I'd use a Dremmel tools (wearing glass & gloves) cutting the plastic around the broken pin to clear its remaining part out.

Following the path on the flex circuit board, solder a 30 AWG wire-wrap wire to restore the connection
(between the cleared pin of the IC & the point where it's connected to). Keeping the flex circuit intact, of course.

HTH, Pyerre

Thanks, this is one option I was thinking about. Soldering so close to the chip is dangerous or not ? I was also thinking about soldering a pin taken from a DIP IC, so that it would allow contact to the flex circuit just like the original pin.

Merci beaucoup.

>>Soldering so close to the chip is dangerous or not ?<<

- Yes, indeed ! Heat & ESD would hurt electronic devices.

Soldering a pin taken from a DIP IC is a good idea.

Suggestion :

- Made some setup, take care about ESD before doing anything.

- Solder one side of the new DIP IC pin to a long wire.
This make life easier to handle the pin & dissipating heat while soldering its other side back to the IC.

- Gently remove the long wire from the new pin after work & here you go.

I've fixed broken IC pins & did have some success that way.


About the 28S -

This thread talking about the 28S malfunction :

http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv003.cgi?read=4841

HTH