12C on the blink



my 12C stopped working after i dropped it (on the carpet). i changed batteries (it has only 1 battery). If i press with my fingers the area around the LCD, the display comes on and it works, but if i release the pressure on the area around the LCD, the screen goes blank.

Can i do anything to fix this?? Everyone i talk to, tell me that the 12c can never break, but mine has gone on the blink after just 2 yrs of use ...

any help will be much appreciated..



Hello, Anand;

please, can you tell us what sort of battery does your HP12C use? Is it the one with one single, flat-buttom type battery?

I've repaired some Voyagers (HP10C, 11C, 12C, 15C, 16C) and all of them showed a good capacity to resist to external harm. I could repair almos all of them, except one: an HP11C with a deffective CPU. This one was the donnator of an integrated circuit (IC) used in all earlier Voyagers to scan the keyboard. I used this scan IC in my first HP16C that had two key columns dead. A few months ago I mixed an HP11C with an HP15C and I rebuilt the HP15C with parts of both machine. A true Franken-Voyager. As you may see, these little babes are indeed unbreakable.

About the HP12C. Last year I got one HP12C that had the following symptom: when batteries were inserted one could see randomly blinking lit segments. I opened it - a mid-type with three batteries and one single IC - and resoldered all IC's terminals. Its owner told me it is working fine after about one year.

They are indeed unbreakable.

It seems to me your 12C has a problem related to bad contact in the battery polse. Have you noticed if you press the area closed to battery? The battery lies under the right side of the LCD if you look at the calculator's front side. Maybe you are in fact pressing the batteries contacts instead of the LCD's contacts. If yours is a single-battery type, slightly tighten the battery compartment screws (two little ones you see when removing the battery cover) may bring yours back to normal operation. These two small screws are Phillips-type, and you'll need a small Phillips screwdriver.

I hope you have success.

Luiz C. Vieira - Brazil


I found a 12C in the street on election day 1988. I was waiting for the bus to go to work after voting. I always find interesting things in the gutter and this time I saw a button cell and nearby a couple more. Next I saw the aluminum bezel from the display and then a few feet away, the rest of the calculator! (I knew what it was because my company provided a 16C to use at work.) The plastic under the bezel showed white stress marks over the screw bosses, indicating it must have been run over, I think, but it was not deformed. The battery cover was missing. I scanned the gutter and the pavement nearby looking for the battery cover with no luck. I saw the bus coming a few blocks away and figured I would have to give up. Then a car drove past me and I heard a tiny tinkling sound in the middle of the road - it was the battery cover!

On the bus, I installed the batteries and everything worked except one segment of the display. Later I disassembled the unit (it is the single PCB version) cutting all the heat stakes holding the keyboard together to reseat the LCD and the missing segment began working. Of course, then I had to deal with how to reassemble the unit, but the experience made me an HP calculator fanatic and readied me for the day when I discovered the HP Museum!



More than once I've found myself walking down the street, day-dreaming about finding an HP-16 in the gutter. Your story has built up my hopes. Thanks!


PS, Now about that HP-16 you had at work... :-^


That HP16C I left at work, although at the end I don't think there was anyone left who would have missed it! I have wondered what happened to it. But while I was still working there I got my own 16C in the form of a warranty replacement unit from EduCalc. They used to send out catalogs quite frequently and one time on the inside front cover they advertised HP15C's for $35 and 16C's for $30, just the calculators, warranty replacement units - like the 42S's HP Parts sold a few months ago. I tried to order one of each but by the time I called they were out of 15C's.

I just dug up my collection of EduCalc catalogs to refresh my memory. They first show up in catalog #56, Summer 1992. HP11C for $29.95, 15C and 16C for $34.95 (calculators only, with 1 year warranty - at least with the 11C and 15C) and 82240A IR printer complete for 74.95 (because the -B had replaced it for $115.95 [$135 list]). In catalog #57, Fall 1992, they only had the 16C and the 82240A, same prices. I don't remember if I asked about the 11C. I was familiar with the 15C because a co-worker had one. Another co-worker had a 71B and three others had 41C's, although two of them owned the same one serially, which I then became owner of! Around this time Educalc was letting people trade-in their older HP calculators toward an HP48S/SX and then selling the used calculators. I got a 71B with HPIL for $89 and a 41CX, what would now be considered "NIB" down to the pamphlets, for $80. I also got various memory modules, application pacs, HPIL, wand, etc. for the 41 as used or closeout. I ordered an 82240A at the closeout price when I got a 41C IR module and they sent me a -B!

EduCalc was great. I got a few more bargains when Jim Carter had a final closeout of his remaining stock (as reported here - this was several years ago) including another warranty replacement unit - a 14B, which is a pretty decent little financial calculator, the first Pioneer I owned. I think he was selling them for $5! When the box arrived, I found he had thrown in several EduCalc coffee mugs and a leather HP48 memory card pouch - maybe one day I will be able to afford a card to put in it!

As I recall the trade-in program, I wonder if they were taking in any LED calculators? They were taking 41C's and the 34C came out the same year, I think. I guess I wasn't aware of the LED calculators and didn't think to ask. Thumbing through the catalogs, I see they were selling batteries and chargers for the older units.

Another thing I wonder about the trade-in program - how many people got caught up in the hoopla about the 48, traded in the 41C's and 71B's, and then regretted it?

I looked up the details of the trade-in program in catalog #56 and they actually had two programs: $45 credit for a 19B, or $55 for a 19BII, towards a 95LX; or $45 credit for a 41CV, or $60 for a 41CX or 28S, towards a 48SX ($274.95, $350 list). It doesn't specifically say you can trade-in towards a 48S ($154.95, $199 list). It also says that if you prefer to keep your old machine until the new one arrives, you can send it in later and they will send a refund. All trade-ins had to be in working order with all manuals. In the same catalog #56 the only used calculators they were advertising for sale were 17B ($49.95) and 19B ($79.95) - with manuals and EduCalc 6 month warranty - and the HP75D/9114B disk drive/2225B printer package ($279) with manuals and 30 day warranty (yes, I bit on that one too). Catalog #57 had the same trade-in programs and used calculators plus a page of 71B's both used ($89.95) and new surplus ($159.95), both including HPIL module and 1 year EduCalc guarantee (manuals extra), along with a list of accessories.

By catalog #61, Fall 1993, the 16C's and 82240A's were gone, the trade-in programs were: $45 credit for a 41CV, or $60 for a 41CX or Card Reader, or $50 for a 48S, or $95 for a 48SX towards ... doesn't actually say but it is on the page after the 48G ($134.95, $165 list) and 48GX ($274.95, $350 list), and $200 credit for a 95LX with 1MB RAM towards a 100LX ($719). The used calculators were 28S ($79.95), 48S ($65), 48SX ($129), and 95LX1BM (call for price), and the 71B new/used reduced to $129.95/$79.95.

Going back a little, catalog #54, Winter 1992, had the same trade-in programs as #56 but the only used equipment advertised was the 75D package and they were still selling 41CX new for $184.95 ($249 list) although it says HP had already discontinued it. Also mentions EduCalc had a separate 41C/71B/HPIL catalog.

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