HP 15C LE (or new 12C) disassembly
01-29-2014, 01:59 AM
Post: #1
 Mobius Junior Member Posts: 2 Joined: Jan 2014
HP 15C LE (or new 12C) disassembly
I've got an HP 15C LE with an unresponsive key. I'd like to disassemble it to clean the contacts. Are there any special instructions I should follow to avoid breaking it by tearing an LCD ribbon or something similar? Or is it quite simple with just a few undoing of screws and some popping of tabs?

01-29-2014, 01:04 PM
Post: #2
 Tugdual Senior Member Posts: 754 Joined: Dec 2013
RE: HP 15C LE (or new 12C) disassembly
http://www.eevblog.com/forum/reviews/hp-...n-and-why/

If that helps...
01-29-2014, 01:04 PM
Post: #3
 Jeff O. Member Posts: 182 Joined: Dec 2013
RE: HP 15C LE (or new 12C) disassembly
(01-29-2014 01:59 AM)Mobius Wrote:  I've got an HP 15C LE with an unresponsive key. I'd like to disassemble it to clean the contacts. Are there any special instructions I should follow to avoid breaking it by tearing an LCD ribbon or something similar? Or is it quite simple with just a few undoing of screws and some popping of tabs?

Take a look at this thread and pictures found here.

Dave - My mind is going - I can feel it.
06-14-2016, 12:18 PM (This post was last modified: 06-14-2016 12:18 PM by Alejandro Paz(Germany).)
Post: #4
 Alejandro Paz(Germany) Member Posts: 117 Joined: Mar 2016
RE: HP 15C LE (or new 12C) disassembly
Quote:I purchased 6 HP 15 LE

No wonder the supply dried out
06-14-2016, 03:15 PM
Post: #5
 Thomas Radtke Senior Member Posts: 751 Joined: Dec 2013
RE: HP 15C LE (or new 12C) disassembly
(06-14-2016 12:18 PM)Alejandro Paz(Germany) Wrote:
Quote:I purchased 6 HP 15 LE

No wonder the supply dried out
It was HPs decision to not continue the 15C LE. You cannot blame its buyers for emptying the stock.

Besides, this was not a fire sale. Interested people could get one for $90 or below for several weeks or even months, don't remember exactly. Unfortunately I bought only one. 06-14-2016, 04:09 PM Post: #6  Marcio Senior Member Posts: 438 Joined: Feb 2015 RE: HP 15C LE (or new 12C) disassembly (06-14-2016 03:15 PM)Thomas Radtke Wrote: It was HPs decision to not continue the 15C LE. You cannot blame its buyers for emptying the stock. +1 (06-14-2016 03:15 PM)Thomas Radtke Wrote: Besides, this was not a fire sale. Interested people could get one for$90 or below for several weeks or even months, don't remember exactly. Unfortunately I bought only one.
Does it have any hardware problems?
06-14-2016, 04:21 PM
Post: #7
 Thomas Radtke Senior Member Posts: 751 Joined: Dec 2013
RE: HP 15C LE (or new 12C) disassembly
(06-14-2016 04:09 PM)Marcio Wrote:  Does it have any hardware problems?
No, allthough it comes from the first batch.

The real problem is the hard coded key time-out value. I suspect every 15C LE will once in a while (every couple of hundred keypresses or so) show double registered entries. They appear real fast, so that a slightly higher value would have eliminated this problem.
06-14-2016, 04:46 PM
Post: #8
 Marcio Senior Member Posts: 438 Joined: Feb 2015
RE: HP 15C LE (or new 12C) disassembly
(06-14-2016 04:21 PM)Thomas Radtke Wrote:  No, allthough it comes from the first batch.

The real problem is the hard coded key time-out value. I suspect every 15C LE will once in a while (every couple of hundred keypresses or so) show double registered entries. They appear real fast, so that a slightly higher value would have eliminated this problem.

The new 12C also has this problem. I had one that would double register a bit more frequently than every 100+ presses. Had to sell it. That however, brings a new question to the table: If the firmware was not meaningfully modified, could this problem be related to some hardware incompatibility? The bugs in the 15C LE, being related to the UI mostly, supports this theory.
06-14-2016, 05:16 PM
Post: #9
 Thomas Radtke Senior Member Posts: 751 Joined: Dec 2013
RE: HP 15C LE (or new 12C) disassembly
I imagine relying on the original 15C de-bouncing algorithm wasn't a good idea if that's what happened. Even if the different speeds are compensated for by some means, the hardware is different.
06-14-2016, 06:39 PM
Post: #10
 Csaba Tizedes Senior Member Posts: 467 Joined: May 2014
RE: HP 15C LE (or new 12C) disassembly
(06-14-2016 04:09 PM)Marcio Wrote:  Does it have any hardware problems?
The real problem is...

Why the old equipments are works more perfectly than the current ones?
Maybe the engineers knowledge today is a piece of s...?
I don't think. This is true for lots of them but I guess the engineers at HP don't do that.
I think the difference is the conscience.
If the designer of these calc is agree that his picture with a short bio appear in a HP Journal, he is a good engineer.

Simple self test: every morning every designer must to ask himself in the bathroom mirror: I am an engineer? Can I make my job perfectly or I am a liar?

Deep inside everything is really simple.

Csaba

Debouncing
06-15-2016, 06:23 AM
Post: #11
 Graan Member Posts: 96 Joined: Dec 2013
RE: HP 15C LE (or new 12C) disassembly
What was standard quality before is now named premium quality. You have to pay more to get a reasonably working product now unfortuantely.
06-15-2016, 09:15 AM (This post was last modified: 06-15-2016 10:33 AM by Alejandro Paz(Germany).)
Post: #12
 Alejandro Paz(Germany) Member Posts: 117 Joined: Mar 2016
RE: HP 15C LE (or new 12C) disassembly
Even if I would pay, say 500, for a premium quality 15 or 50g, there are none available, and there were none available at the time the 15LE was on the market.
The 50g costs much less than what a 15 used to cost in the 80s, and has much more power and functionality. Inflation and everything. But, from what we can read here, the 50g is also of regular quality at best .
On my desk, I can admire a 41CV made in '83..84 (2414A). The display has great contrast, all keys work, they have... that feeling. OTOH, the 48gx ('96) I have, have nice keys but they are the plastic bubble sort, still better as what is described here for recent models... but a far cry (imho) to those metal-dome keys.
06-15-2016, 12:54 PM
Post: #13
 Ron Ross Junior Member Posts: 47 Joined: Mar 2014
RE: HP 15C LE (or new 12C) disassembly
About quality and cost. The Hp 15c LE was simply a fan boy calculator as many have said. IT WAS NOT a real Hp 15c, as it was an unreliable calculator for programming and a worthless low battery indicator. Both would be fatal flaws for the original Hp 15c when it was released. Today, not so much because in this day and age, nobody should use the Hp 15c as a primary lifting tool for design. It is a desktop number cruncher, made to replicate an earlier calculator for nostalgic use.
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Perhaps Hp or Swissmicros can make a real competitor to the original line. I suspect Hp would need \$150-200 per calculator to actually sell and support such a calculator. Swissmicros seems to be able to do so for somewhat less (but the overhead of a BIG company isn't there).
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The Hp 50G's actual keyboard has always reminded me of my earlier Hp 49G+ keyboard, except it didn't break, just felt too similar and due to my experience with my earlier Hp 49G+, CHEAP. Hence, while I liked my Hp 50G, I never loved it.
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Most engineers talk the talk about buying a decent number crunching calculator, but most are fine with a decent Ti scientific. These guys buy the best value for the buck ie a Ti-36 pro or Casio fx 115. Aside from the ability to program and the venerable Hp keyclick, the Hp 35s falls short of these two calculators for value. I wouldn't compare the Hp 35s if it were a reliable programmable, but that isn't the case. Without a reliable low battery indicator and byte count for proofing programs, I don't use the programming of my Hp 35s.

Then there are a few calculator snobs who want the best and will actually pay for the best. However, 10,000 (maybe 20,000 if you trust the Hp serial number count) Hp 15c LE's were sold, a very high end scientific pocket calculator to placate some of this market. If we extrapolate (ie make up some numbers) that the market is 10X (or evern 20X) this size, that still only means 100,000 high end calc users for potential sales (key word potential). Most of these potential sales might or will be happier with the Hp Prime, Ti Nspire or whatever other high end calculator, and will not settle for a 30 year old rpn Hp pocket calculator.
06-15-2016, 01:49 PM
Post: #14
 Thomas Radtke Senior Member Posts: 751 Joined: Dec 2013
RE: HP 15C LE (or new 12C) disassembly
(06-15-2016 12:54 PM)Ron Ross Wrote:  The Hp 15c LE was simply a fan boy calculator as many have said.
It was advertized as Great Gift, so not even HP took it serious.
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