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HP Forum Archive 06

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HP-34C problem: battery pack?
Message #1 Posted by Dan Kalish on 18 July 2001, 11:47 p.m.

I just acquired an HP-34C and it is a delight, but has an intermittent problem. Digits will drop out of the display partially or fully. Knocking the calculator to reseat the battery pack sometimes helps.

Also, the battery pack doesn't hold a charge. Without the charger, the dot light on the left goes on almost immediately.

Any ideas? Sounds like a battery pack problem to me. The seller had built a battery pack according to instructions from an article in this Museum. I can't find those instructions. Does anyone (such as David) know where that article is? It would be for a Spice battery pack.



Re: HP-34C problem: battery pack?
Message #2 Posted by Tony Duell on 19 July 2001, 7:14 p.m.,
in response to message #1 by Dan Kalish

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.

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