EEVblog #582 - HP41CV Teardown

[senso]

Its like an expansion ROM filled with programs?

[HP-ILnerd]

In the case of the Math pac, yes.  Programs.   Sometimes the modules just add functions in hardware.  There are even custom ROMS that were made if they were ordered in sufficient quantity (min was 5000).  It may speak to the nature of the era when these were made that there was a Nuclear Weapons Air Burst Effects module made.

[phamuc]

For all that love HP calculators.
You can get your free official HP calculator (Emulator).
You have your choice of 10S, 300S, 15C, 35S, all with Full manuals in the help function!

http://www.hp.com/sbso/product/calculators-emulators/scientific-calculator-emulator.html

My favorite is the 15C, its look and feel (OK the feel is psychology, I own a real 15C) is incredibly!
I wish there was also a 16C Emulator.

The only thing that sucks with these calculators, is you can't do a tear down of them.
But you should NEVER do a tear down of a HP!
and I hope Dave does NOT tear down (break) the HP41CV! Dave, I vote NO!!!
Save the HP41CV! Long live the HP41CV!

-Paul

[johanan]

Don't kill it. I am almost sure there is nothing but the lcd display at the bottom.

[electronics man]

Dave dont go any further it would be terable to kill something like that, find a dead one and then rip that one apart.

[HP-ILnerd]

Dave,

A dead one might be interesting in and of itself, since why they are usually dead is a good lesson on how not to store your electronics: You will see often see used or even possibly unused ones on ebay where someone left the batteries in for years.  Since the 41 draws while it's off, I've seen tons of sad looking units that have had their battery contacts eaten to green powder.  Some of those get broken down and sold for parts.

If anyone is looking to get a (good) one, make sure they show battery contacts, and make sure they show it on, close-up on the display, make sure they mention
the state of the keys.  There are a few US sellers I'm comfortable with, and I have no idea where they keep turning up nice new specimens, but they do.   Case and manuals are also helpful.

The original HP-41 manual is the only manual I ever actually read cover to cover, and is a model of how a good manual should be written.   There's copies of all the manuals for nearly everything at the http://www.hp41.org/ website.

[Edited for spelling.  Good grief, need more coffee]

[HeywoodFloyd]

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!

This sounds like the TI59 or 58: http://en.wikipedia.org/wiki/TI-59_/_TI-58. I am the proud(ish) owner of a TI-58C, still in its original box and with manuals, but it doesn't work any more. I actually used the thing myself at uni, and people were laughing at me for having a (by then) ancient calculator with LED display. I remember programming it, writing code for all its 480 bytes    And I seem to remember it took it tens of seconds to do a complex square root...

I also vote don't destroy the HP... IMHO one should not destroy stuff that works - not even to figure out how it works. And I like HP calculators. RPN - nice.

[linux-works]

about 10 or 15 yrs ago, someone on the local usenet group (remember when they were still non-binary and non-spam?) wanted to give away a free hp41 that was non-working.  I took him up on the offer.

here is my flicker shoot of my repair:

http://www.flickr.com/search/?details=1&w=47907743@N00&q=hp41

the motor in the card reader was gummy (of course).  and the wires to the lcd (elastomer) was bad so I bit the bullet and hard wired it with kynar.  works fine and is more reliable now than with the rubber baby buggy bumpers

I never use the 41, though.  I bought a used hp25 which I like better, for some odd reason.

[linux-works]

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!

lol.

reminds me of the steven wright joke:


I bought a new phone though. I didn't have much money so I had to buy an irregular phone -- it had no number 5 on it. I saw a close friend of mine the other day... He said, "Steven, why haven't you called me?" I said, "I can't call everyone I want. My new phone has no five on it." He said, "How long have you had it?" I said, "I don't know... My calendar has no sevens on it."

[SeanB]

I have 2 TI58C I bought on auction years ago. Dead ( really dead on the one and growing blue green fuzz all over, missing on the other) and no power supplies either, and cosmetic damage. Cleaned them up a little and bodged in a simple 4V8 zener diode as a battery replacement. Interesting way they stacked chips in them. think the memory capacitor is very dead now though. Must pull the photos off the camera and post them up.

[rjk5378]

reminds me of the steven wright joke: ...

Another Steven Wright bit was something like: "I bought a new camera. It has lots of features. It's so advanced you don't even need it."

[SeanB]

Well, opened it up and took a few photos. Interesting in how they stacked the assorted chips to increase density.

[HP-ILnerd]

Linux-works:  Nice job fixing those, and spectacular photos!  Amazing how no one anywhere seemed to realized what would happen to the gummy wheels over time.  I have an HP-97 that works perfectly (cosmetically fine, too) but needs to have its gummy wheel replaced.  It's on the list of things to do when I finish up my new bench...

SeanB:  How much of that main board is factory?  Also, is that hot glue on the display?

[Wytnucls]

My TI 58C is much different inside. It is original, apart from the battery contact springs, which corroded a long time ago.
The TI quality is very inferior to the HP workmanship.
No stacked chips in this one.

[SeanB]

Only bodges are the epoxy on the cracked display on the front, and the zener diodes and capacitors replacing the battery clips which rotted away from the battery failing. The display has a cover to hide the crazing and scratches, must look to replace it or polish it, but it does not worry me. All the stacked chips and such are original, this is a very old unit, probably was made when I was still in school. It has a slightly bouncy keyboard, but still does all that it needs to.

[Hydrawerk]

I have one, too. But I do not like RPN.

[SeanB]

You need to dust it......

[sa-penguin]

This is now considered an old thread, but I just joined in order to say:
"Don't pull the old HP-41 apart, unless you can GUARANTEE you can get it together again".

If anything, this should be considered an exercise in quality manufacturing: using modern assembly techniques, is it possible to make a custom keypad to this quality level?

Seriously, there are calculator enthusiasts who re-purpose the HP-30b into the WP-34S.
They are trying to make a whole calculator from scratch (WP-43S) but it's slow progress.
Some insight into how to make a keypad, as good as the one on this 41 model, would be appreciated.