Non-working Wand



#2

I've got a non-working wand for my HP-41. The LED lights up, but it doesn't read any barcode. Turning on the calculator by the wand doesn't work, too. Is there anybody out there who has experience in repairing wands? Any help highly appreciated!

Thank you,
Juergen


#3

There's a schematic for the 82153 Wand on the HPCC schematics CD-ROM....

Anyway, there are 3 wires in the cable. IIRC they're black (ground), red (Power) and white (signal). I'd start by connecting a 'scope or logic probe/analyser to the white wire and trying to scan some barcode. If you get transitions on the white wire, then the wand itself is working, the problem is either the HP41 connector or the direct-on-board chips in the module. If the wand itself is the problem, you can open it up (it is glued together, but it can be separated) and look at the PCB. There's a dual op-amp chip and a few standard components there.


#4

Ooops... The schematic isn't on the current version of the CD-ROM (I handed a bit of paper with it on to Dave Colver to stick on the next version, though). I am sure if you ask him nicely he'll find a way to get it to you....


#5

Thank you, Tony, for these hints. I was not aware that the wand service manual is on the TOS DVD. Just started to read it; hope it helps.

But if the chip is faulty I guess there is no big chance to repair it. And to open the wand, you have to crack the body! A rather destructive act. Not as easy as replacing the gummy wheel in a card reader.


#6

If the HP41 module (and therefore the 2 direct-on-board chips inside it) is good, you can probably fix the wand. The chip inside the wand is a standard part. In any case the module can be used with a little add-on circuit to download programs into the 41 (without needing an HPIL interface).

I have opened up wands non-destructively. Yes, you can see they've been taken apart -- slight marks in the plastic -- but they are still very useable. HP service manuals often tell you that case parts need to be replaced when they don't -- HP service centres sent the thing back in as-new condition with no marks, etc....


#7

Quote:
In any case the module can be used with a little add-on circuit to download programs into the 41 (without needing an HPIL interface).

That sounds interesting. Is there any documentation about this? I guess it requires some software on the PC.


#8

I already found the information on the HPCC site.


#9

Hi Juergen,

I'm also interested in doing this. I couldn't find the info on HPCC. Could you point me to the info or do I need to be a member to access it.

Thanks,

Bill


#10

Get the LIF Utilities for Linux from

http://www.hpcc.org/datafile/hpil/lif_utils.html

The information (ascii-art schematic, PIC source code, etc) to make the interface is in there. So are the linux programs to turn HP41 program and data files into barcodes. You are welcome to port those to other machines.


#11

Thanks Tony. I'll take a look at them. Will give me an opportunity to load Linux on one of machines.

Bill

#12

Tony Duell on 29 Jan 2005, 2:35 p.m., wrote

> ... the module can be used with a little add-on circuit to
> download programs into the 41 (without needing an HPIL interface).

Yes! I remember in the early 80s I dissasembled the HP-41 interface of my second wand (won as a reward for contributing programs to the European Program Library -- UPLE), and connected it to the user port of my BBC micro.

Later I found out that I could enter programs by touching the tip of my other (intact) Wand to the CAPS LOCK LED on the BBC keyboard and then pulsing the LED under program control.

Almost 20 years later I found out that I could have burned the sensor on the Wand if the external LED was too bright. Ignorance is bliss :-)

**vp

PS I also connected the Wand (sans HP-41 interface) to the joystick port of my BBC to read barcodes distributed by a UK magazine called (I think) BBC Micro User.

The wand interface is just three wires, +5V, GND and TTL output.


#13

I've fitted an optoisolator chip inside the HP41 module of my Wand, details are in the LIF Utilites for Linux distribution. The LED side of the optoisolator goes to whatever I want to use to send data to my 41...

As regards burning out the wand by shining an LED at the sensor, I've seen that reported in PPC Journal, but honestly I don't see how it could happen. Well, not unless you use a laser or something. I would be interested to know exactly what fails when you do this.

#14

Dear Juergen,

While I'm sure Tony's suggestions are very good, I would advise you to try some simpler things first.

My experience with the wand is that it is VERY temperamental. If the LED lights up, then you might try scanning bar codes in the only way I found that works, which is with a ruler.

That is, take a nice thick ruler, line it up perpendicular to the barcode, and sweep your wand at about a 30 degree angle smoothly across the barcode.

I'd be interested if it works.

Good luck,

Ion Abraham
Albuquerque, New Mexico, USA


#15

I have another wand which works fine so I know "the beast". I suspect that one of the electronic parts is dead... :(

But I don't like to throw away these fine HP stuff. That's why I try to repair the wand.


#16

Dear Tony,

your program download application sounds interesting, also your hardware modification - using an opto coupler.

What do you thing about an external keyboard (there exist some nice and small keyboards for notebooks and laptops) for HP41 : Between the keyboard output and the wand module input we need a cpu for generating the TTL level input signals for the wand module. With this hardware application we are able to input alpha text, and some control comands like ALPHA, PRGM, USER and so on to HP41....


Please give a response about this idea...


Regards - Christoph Klug


#17

Sounds like an interesting idea. You could use the 'paper keyboard' codes, but of course that would prevent you entering syunthetic program instructions. But I can't (off the top of my head) think of a simple way to get round that.

I think a keyboard with the PC/AT (or PS/2) interface would be a lot easier to use than one with a USB interface. You'd need a microcontroller between that and the wand module. You're welcome to make use of the code (and schematics) that I used, of course.

I have, somewhere, the notes I made on what the wand output looks like when you scan a row of barcode. If it's not obvious from my source code, I'll look it out.


#18

Tony,

I have done the USB Interface in my MLDL2000 and I can tell you that is is really very simple to use. The only problem is that you need to build a PCB, but there are some DIP size modules available that should work as well. I use the FT2232C from FTDI, have a look at www.ftdichip.com and it is straigthforward to have one of the I/O's blink a led.
BTW, my Wand is broken as well, but the problem seems to be in the ROM as I get no listing in CAT 2.
BBTW, I do not mind very much, since having an MLDL2000 will beat any other connection between PC and HP41 ;)

Meindert


#19

I've not seriously looked at USB (none of the over 200 computers that I own can support it), but I was under the impression that there were 'master' devices like PCs and 'slave' devices like, presumably, keyboards, the MLDL2000, etc. And I was also under the impression that making a slave was a lot easier than making a master. To talk to a USB keyboard, though, presumably you'd have to do the latter.

As regards your wand, if it doesn't show up in cat2, then the HP41 is not detecting the ROM. Since you clearly have an MLDL, I would start by looking at the page where you'd expect to find the wand ROM to see if anything appears. You could also try cleaning the contacts on the wand module and checking the soldering between the connector and the wand module PCB.

Finally, the MLDL is only a solution to linking the HP41 to a PC if your PC supports USB. Mine doesn't....


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