Posts: 1,162
Threads: 26
Joined: Aug 2005
This sounds like bad connections inside the HP34C. On older models of the HP3xE/3xC line, HP used a somewhat odd construction technique with almost nothing being soldered down. Instead, the components were clamped against a flexible PCB with a foam pad under it.
Needless to say, these connections are not that reliable. Start by taking the machine apart. Remove the battery pack. Undo the 2 screws in the battery compartment. Place your thumbs in the battery compartment, fingers on the sloping front of the top case, and squeeze. There'll be a sharp click and the bottom case will move forwards slightly, releasing the catch at the front
Then Free the battery contacts from the bottom case and take it off. Free the battery contact PCB from the top case, and keeping machine upside-down, free the electronics from the clips along the sides (3 each side). Take out the electronics. At this point, the keys and switches (and their contacts) are loose in the top case, don't drop anything!
Take off the 2 metal clips along the sides of the electronics. With the unit keyboard-side up, lift off the PCB assembly. You'll be left with a plastic frame containing the chips and the PSU module. The display is at the top of this frame, and will probably fall off!
Clean the pads on the PCB and the pins of the display and put it all back together again. I've fixed a number of 3xE/3xC machines by doing this.
