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...
Thanks.
Mike T.