EEVblog #582 - HP41CV Teardown

[moemoe]

Now that's commitment

That's the legendary "german gründlichkeit"

But to return to the original question: No, dave, don't tear it apart further. There is not much of interest on the other side: http://www.keesvandersanden.nl/calculators/hp41cv_inside.php

[smashIt]

Casio fx-82 is 4 life.

PHA!
ti30 is best calculator evaaaaaaaaaaa

[EEVblog]

PHA!
ti30 is best calculator evaaaaaaaaaaa

The Casio FX61F rules. It has dedicated electronics buttons!

[RupertGo]

Don't take it apart any further - what would we see?

But a couple of questions. Where does the processor get its clock from? I didn't see any resonator or crystal on the board. Wasn't that inductor, was it? Bit chunky.

Also, at 17:00 and thereabouts during the close-up of the display connections, there are two fat PCB fingers that veer towards each other and end in what you'd expect to be vias - but aren't. What's that about? It almost looks like a spark gap, but I'm having a hard time believing that.

You could work out more about the display interface with a bit of scoping. That might be interesting: reverse-engineering interface protocols is a bit of an art in itself, and can only get more so as the global stock of under-documented vintage digital kit grows! And you don't have to saw off the heat pillars...

R

[moemoe]

The Casio FX61F rules. It has dedicated electronics buttons!

My vintage calculator also has electronics 'buttons'

[DavidGoncalv]

Has no stack!

[moemoe]

Has no stack!

Just forgot to take a picture of it:

http://commons.wikimedia.org/wiki/File:PostItNotePad.JPG

[DavidGoncalv]

   Nice!

[Kjelt]

 

[robrenz]

Don't take it apart, that would be a real shame.  There is nothing on the other side that interesting to warrant killing a functioning piece of calculator history. 

[FireBird]

You could work out more about the display interface with a bit of scoping.

The display is connected to the same bus as any other module/peripheral device. It is a 56 bit serial bus, where ROM address (16 bit) and ROM data (10 bit) is transmitted on one line, RAM data (56 bit) on another line. In addition, there are 2 clock and some other control lines. The LCD acts like a RAM, which means that it monitors the opcodes coming from ROMs and if the right ones passes by, it will read the data from the data bus.

[BMac]

Yeah I agree, nothing of interest on the other side of that board to warrant destroying such a beauty!

BMac

[RupertGo]

Thanks, Firebird! Does the display look for opcodes or addresses, or are they combined?

Something like the HP calculator is well documented anyway, but I still think it would be fun to see Dave do a bit of protocol analysis. One of the more engaging aspects of the fault-finding and fundamentals videos is actually using all that lovely test equipment, so a live teardown appeals a lot...

(happy thoughts of a live teardown on a 5kW VHF amplifier final...)

[FireBird]

Just for the opcodes because RAM and ROM address space is separated. These special opcodes are NOPs to the CPU but trigger some action in the peripherals.

[Kompost]

There's no way around it, it's time to go in Mike's footsteps and get yourself an x-ray machine 

[Wytnucls]

This is the board of my 41C, serial 2213S44694. Bought in the eighties, if I recall properly.

[RadioGeek]

Hey Dave, great tear down, but don't go any further.  Would be a shame to tear up that classic!

[TheWelly888]

Another one here saying, don't tear the board out! As long as the calculator is working, it's worth keeping.

It's not worth taking a calculator fully apart as the keypad side of the board is quite boring. Though I once took my Casio FX100c apart out of curiosity, yawned at the keypad then re-assembled the keys. A few days later, my Physics teacher borrowed my calculator to show me the result of something and he could not understand why he was getting a nonsense answer until I realised I put the + and - keys the wrong way round!

[(In)Sanity]

Don't take it apart,  turn it on.....and use it.

[rjk5378]

I vote NO!! Don't destroy it. However, it should not be too much problem to locate and acquire a non-working or "for parts only" model that you could tear up. <g>

I'm the proud owner of an HP-41CX (that I still use). I had an HP-41 (with extra memory modules) from 1980 until 1994 when I absent-mindedly left it in a hotel room. The engineering and design of the calculator itself was, of course, a thing of true beauty. But also impressive was the documentation. The 41-CX had, in addition to the quick start guide, a two-volume manual spanning nearly 400 pages. Everything was laid out clearly. Not only operation of the unit, but the programming as well. One who had no computer programming experience could, by learning to use this calculator with that manual, get a very good foundation in programming concepts.

My office at the time had the competing high-end calculator made by Texas Instruments. I can't remember the model number, but in order to get alphanumeric on it, you had to plug it into a larger units (approximately the size of a small portable typewriter) and it would print the information on a paper tape roll. Not just the results, but the interactive alphanumeric prompts, etc., as well. But without that extra unit, you had to rely just on the numbers in the display (red LED's if I remember correctly). Still, to me that was impressive at the time, and I was thinking of buying one for myself. A colleague dissuaded me. He loaned me his HP-41 and manuals for a weekend and, as he predicted, by the time I came back on Monday morning, I was sold on the HP. Went out and bought one at lunch time that day, and never gave the TI model another thought!

I still use my HP-41 today. It sits on or near my desk, and I grab it when I want to do quick calculations. I have newer calculators, but truth-be-told, I am all but helpless without Reverse Polish Notation. <g> Except for an occasional nostalgia fix, I don't run programs on it any more, basically because it is slow. The kinds of things I sued to use the HP-41 to solve, that would in some cases take the better part of a minute and occasionally longer, can usually be had instantaneously today with the single click of a mouse on some web site. But I am nevertheless still in awe of the accomplishment that was this calculator.

-- Bob, KY3R

[rjk5378]

Has no stack!

Just forgot to take a picture of it:

http://commons.wikimedia.org/wiki/File:PostItNotePad.JPG

LOL. I think you got your stack from the same place where they sell DaveCAD. <g>

[calexanian]

I also vote to leave it be. I would be more interested in seeing what the most complicated program it could run and how long it would take to arrive at the solution.

[HP-ILnerd]

That could actually be a while.  One thing it isn't, is particularly fast.  What it is, is flexible.  The programing language "Forty One CAlculator Language" (FOCAL) is amazingly expressive for something runs on a calculator.  It's capable of both indirect addressing and indirect execution, allowing you (in effect) to construct arrays or implement jump tables.  Plus, via the User key, it's set up so you can re-define almost every key on the keyboard to execute a program or subroutine simply by assigning it to a key.  If you have the Extended Functions module, or a 41-CX you can have a program reassign the keys, allowing you to configure the whole calculator for whatever it is you are doing.  If you are an undisciplined programmer, you could make a horrid mess of spaghetti-code, but that said, it's nearly impossible to lock up the machine with anything in its instruction set.  It's "synthetic" programming capabilities are a different matter.  That lets you get at functions that were not for user use, and are dangerous to use casually.

Other fun peripherals:
The Time Module:  Created at NASA's behest, this allows you to have programmable alarms that put the calculator to sleep, wake up at a predetermined interval, do something, then according to conditions set another alarm to do it (or something else) again, etc.  There's one guy on one of the calculator forums who reports a 41 running an  HP3421 data acquistion module to operate lawn sprinklers.  The 3421 has a 5 1/2 digit multimeter built in, so you could (say) periodically (via the time module) measure sunlight with a photocell and turn on the sprinklers (it has relays built in) when it was too sunny.
The applications are really limited by your imagination...and it's pokey clock speed.

Excellent resource:  http://www.hp41.org/Intro.cfm

If you have an iPhone, there is a phenomenal 41CX emulator available for it.  I've written programs on that, had it email them to myself, made barcodes, read them into a real 41 via the barcode wand.

[senso]

Whats inside that MATH card?

[HP-ILnerd]

From the manual:

Matrix operations,
Solution to f(x)=0 on an interval
Polynomial solutions/evaluation
Numerical integration,
Differential equations
Fourier series
Complex operations
Hyperbolics
Triangle solutions
Coordinate transformations (2 and 3d)