HP34C Keyboard Problem


I'm having a bit of a problem with my 'spare' HP34C, basically everything works except the second column of keys (B, GTO, ENT, -, +, x, /) which do not register unless I push hard on the back of the calculator roughly behind the 7. Then all these keys register and the machine passes the self test.

I've opened it up and it appears to be an early model in which someone has carefully soldered the chips to the flexible PCB during a previous repair. I managed to obtain a copy of the schematic and have (I think) traced the most probable connection path but though I feel sure it must be a dry joint somewhere I can't spot it - and would not feel comfortable attempting to solder it anyway as this is how I killed my original HP33C. (A very kind electronics examiner once remarked that I would make a good plumber - so you get the idea.)

I'd like to get it back into full working order again if possible...


Mike T.


Mike --

I assume that you know about the differences in construction between "older" and "newer" models (and may have alluded to it with "carefully soldered the chips to the flexible PCB").

The (newer) soldered design debuted sometime in 1982. Models made that year will have serial numbers beginning with 22.

-- KS


Try our friend Randy and FixThatCalc.Com


It is the older type - and as it is my spare I wasn't contemplating spending a fortune on it as has been well used in the past and is rather worn.

I doubt it is worth sending it all the way to the US as I'm in the UK..


Mike T.

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