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HP Forum Archive 02

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HP 34c
Message #1 Posted by Jim on 12 Jan 2000, 5:47 p.m.

I have a HP 34c and I haven't used it for years. It is not working at all, no display information or anything. I'm wondering if I need a new battery pack. Would this be a good place to start, and if so, where might I find one?

Re: HP 34c
Message #2 Posted by Randy Smith on 12 Jan 2000, 8:14 p.m.,
in response to message #1 by Jim

One thing to try is regular (non-rechargeable) AA batteries. Pay attention to the polarity and put a small piece of foil at the opposite end of the battery compartment to complete the circuit. If the calculator works, then the battery pack is what's bad. It is easy to rebuild the battery pack in a 34c. All you need is two rechargeables to replace the old ones and a soldering gun. I would suggest going to Radio Shack to get tabbed rechargeables. The biggest thing to pay attention to is the polarity of the batteries. There should be a sticker on the battery pack you already have to tell you which contact is positive and which is negative. Then, after you have replaced the bad batteries, wrap it with a bit a electrical tape making sure not to block the groove too far down between the batteries. This ensures the battery pack only fits one way in the compartment. My 32e has worked like a champ since I rebuilt the battery pack for it. I hope this helps. Randy

Re: HP 34c
Message #3 Posted by DPD on 13 Jan 2000, 11:28 a.m.,
in response to message #2 by Randy Smith

I agree with Randy. Did the same on mine. The old batteries may have leaked acid on the printed circut board tabs and rotted the tabs away. (This happened to me.) Use caution during the disassembly and make notes. Repairing the printed circut board tabs requires a small, moderately hot soldering iron, some pc board trace material, solder flux, and a steady hand. If you are uncomfortable with this repair, track down some amateur radio club members (local phone book or Internet) and I'm sure they would be glad to help!

Re: HP 34c
Message #4 Posted by Joe on 18 Jan 2000, 8:55 a.m.,
in response to message #3 by DPD


There are some things that you need to watch out for when you try to open the case on a Spice model. Follow these instructions and you should be OK.

How to open HP-3x cases without damaging them.

The -3x are VERY tricky to get apart. It's TOO easy to damage the edges when taking them apart. They have to be pried apart and slipped apart at the same time. Also the battery contacts are connected with a film type ribbon and if you're not careful, the calculator will suddenly come apart and you'll rip the cable apart! Practice on a junk one first if you can!

Take battery out of the -3x and remove the two screws in the battery compartment. The bottoms of the cases halves are hooked together. The front case also sits in a groove in the back case half. You have to get the front case out of the groove then unhook the halves.

Pry the case apart at the top about ". WATCH THE BATTERY CONTACTS!!! You have to press them down so that they do not catch on the back case. Be sure that the board with the battery contacts stays in the front half of the case*. Take a thin knife blade and insert it between the case halves and work it down to the bottom. There are several parts just inside the case seam so you have to work past them. Do not try to pry the cases apart, just let the blade separate them a small amount, that gets the front case out of the groove in the back case. Pull the back case down and the front case up to unhook the hooks in the bottom. When you pull on the back case, don't pull against the top of it. It's too thin above the battery compartment and will break. Hook your fingers in the bottom of the battery compartment and pull against it. You can also tilt the back case out more to help separate them. Be very careful not to let them fly apart or you may rip the battery cable apart. When the back is off you can pull the battery contact board out of the slot in the front case. I pry it out by inserting a screw driver blade in the slot in the contact board and prying against the front case.

*If you leave the battery contact board connected to the back case, you'll probably rip the battery cable apart when the cases come apart since the other end of the cable is connected to the circuit board in the front half of the case.

To reinstall the case, place the board with the battery contacts in its slot in the front case half. Press it down to seat it all the way. Place the case halves together and stand them with the top of the calculator on a table and the front of the calculator facing away from you. Grip the calculator with both hands and place your thumbs on the slope at the bottom edge of the back case. Press down with your thumbs to force the bottom case half down and away from you and into the front case. It should snap into place. Squeeze the top of the two case halves together and install the two screws.

Copywrite 1997 H.J. Rigdon. Not to be reprinted without permission of the author.

Re: HP 34c
Message #5 Posted by jim on 15 Jan 2000, 3:21 p.m.,
in response to message #2 by Randy Smith

Thanks, Randy and DPD, I'll give this a try. Appreciate your help! Jim

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