Broken HP 71B. Where to start?

[Maximilian Hohmann]

Hello!

I think that a broken HP-71B is difficult for anybody to repair. Listing it on eBay could however be of interest to someone who needs a spare keyboard or display, so I guess it won't take long to sell.

Two easy fixes that I can think of:

1. Sometimes when the HP-71B was turned off for long periods it requires a very long press (several seconds) of the ON key to come back to life. This is always the first thing I try.
2. Depending on the production year some HP-71Bs come with battery connections that are not made by wires soldered to the PCB but simply the back end of the battery springs that touch a gold plated area of the PCB. I have had contact problems with one of these in the past and ended up by soldering the contact springs to the pcb. The springs are rather difficult to solder though. For testing purposes you can solder wires to the PCB directly and power the calculator from a 6V DC power supply.

Otherwise the service manual can be accessed from here (in case you haven't already downloaded one): http://www.hpmuseum.net/exhibit.php?hwdoc=118

Regards
Max