(12C/11C) Changing the firmware

[NazarK]

Heyo,

So I got a used 11C and had a really hard time figuring anything out. Trigonometric functions weren't working properly and buttons seemed to be remapped. I ran the keyboard test and display test (ON+divide and ON+mulptiply) which worked fine except at the end of the keyboard test, the calculator showed "12" instead of "11".

This led me to believe that somewhere down the line, somebody swapped the motherboard with an HP 12C instead

I looked at some keymappings on the 12C (such as 1/x) and sure enough those worked. Now is there a way to reprogram the ROM to an 11C or do any modifications? I could probably make stickers and turn it into a 12C but honestly I wanted scientific functions.

[rprosperi]

No, it's not possible to change, these machines from the early 80's all use ROM and cannot be updated. The most recent 12C and 15C LE models can be re-flashed, but unless yours uses 2 x CR2032 batteries, it's not one of those, and it sounds like it isn't.

If you got that on eBay (from some unethical, scamming seller that replaced dead guts of an 11C with working guts of a cheap 12C) I would definitely open a case for a return/refund. 12Cs go for $20-50, 11Cs for much more, as you probably know.

[NazarK]

I did get this 11C for about 13 dollars from OLX ("basically ebay") and thought it was an amazing score. There isn't really any way to get a refund though and the seller seemed to have no idea what he had. I asked him about it and he just said "I got this imported from the UK so idk".

Yeah this isn't a recent 12C since it's running on 3 small 1.5v button cells. Has anyone ever made a sticker set for the 12C? I got a 17bii as well (thankfully without any motherboard madness) so I guess this 12C frankenstein is just good as a 4 function rpn calc

[HP-12C]

Bob; is the internals swapping very common on eBay and elsewhere, or just the actions of a few calculator sellers?

[rprosperi]

(04-18-2023 08:23 AM)HP-12C Wrote:  Bob; is the internals swapping very common on eBay and elsewhere, or just the actions of a few calculator sellers?

I would not say common and likely not on eBay since refunds are always available.

I've never experienced it personally, but have heard of two cases (one before this one) where someone put a 12C board into a higher-value Voyager in order to sell it. And while casually casting aspersions above on the sellers, I really can't rule out that they were simply swapping parts among machines on hand which looked alike without knowing more. In the earlier case it was a cheap 12C sheep in expensive 15C clothing, but an 11C here. In both cases, it was purchased via a channel where refunds were not possible.

OTOH, eBay listings for a 12C which are actually an 11C, 15C or 16C, simply because the seller didn't look closely enough, are not at all uncommon. On many occasions when I've seen this, the model # badge is missing, so the seller is doing only a casual visual comparison to other listings.

When I feel unsure about a thing like this, I would ask the seller to conduct a self-test and then send a photo of the result.

[Dave Britten]

Without better evidence, I would opt for Hanlon's razor here and presume that someone attempted (successfully!) to build one working calculator out of a pair of non-working ones, and the seller simply wasn't aware this had happened. That said, unless the item was explicitly sold "as is, without warranty of merchantability etc.", then the seller should process a return and refund for an item that is not as advertised.

[rprosperi]

(04-18-2023 01:31 PM)Dave Britten Wrote:  Without better evidence, I would opt for Hanlon's razor here and presume that someone attempted (successfully!) to build one working calculator out of a pair of non-working ones, and the seller simply wasn't aware this had happened. That said, unless the item was explicitly sold "as is, without warranty of merchantability etc.", then the seller should process a return and refund for an item that is not as advertised.

You are probably right. I meant to comment in my reply seeing the new price info., but got off-track; charging only $13 indeed tends to confirm that the seller either:

1. Had no clue what they were if he created it by swapping parts, or
2. Acquired it as-is, and then just sold it, assuming it was a 12C as the badge would indicate.

Otherwise, if the $13 was for the better, 11C model, he would have had to pay a buyer to take a 12C, lol.

[NazarK]

Well the seller got back to me and just said that if they have another 11C, they would swap mine with it (like that's ever gonna happen lol). His listing did say "11C financial calculator" so I assume he thought it was a worse version of a 12C and that's why he sold it cheap. Shipping it back would cost another $5 so I'd rather just print the 12C layout and tape it on top.

In my free time though maybe I could try putting an EEPROM instead of the ROM it has and put the 11C's ROM on it? It would be a huge pain to get it working but could be cool

[Csaba Tizedes]

(04-18-2023 12:06 PM)rprosperi Wrote:  

(04-18-2023 08:23 AM)HP-12C Wrote:  ... is the internals swapping very common...?

... it was a cheap 12C sheep in expensive 15C clothing...

I'm sure a dead 15C more valuable than a workable 12C and additional time of transplanting...
In this case better to sell them as original, that is much better margin on cost.

Cs.