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John Garza (3665) · 07-03-2023, 06:35 PM

Does anyone have a source for the mag cards for the older HP desktop machines?
Or perhaps compatible magnetic media that can be cut to size?

-J

blackjetrock · 07-03-2023, 08:10 PM

(07-03-2023 06:35 PM)John Garza (3665) Wrote: Does anyone have a source for the mag cards for the older HP desktop machines?

Which machines are these? What size and thickness of card are they?

Quote:Or perhaps compatible magnetic media that can be cut to size?

-J

I've made cards for the Casio PRO FX-1 which are CR80 plastic card sized. I bought blank CR80 cards with Lo-Co magneti stripes then machined the timing stripes on a CNC machine. They work well. I was lucky with the size of these cards as you can get the blanks. I have also made cards for the Sharp PC-1300S whih are not a standard size. For those I used plastic card of the correct thickness and machined the shape of the card out using a CNC machine. To get the magnetic stripe on the card I managed to find and buy some self adhesive Lo-Co magnetic stripe material. That has to be cut to the correct width and length and be stuck to one side of the card.
I've had a quick look and it looks like you might be talking about a 9100? They seems to be larger cards, a bit like my Rockwell 920/3 cards. It looks like it would be feasible to make then out of plastic card with several self adhesive stripes stuck on a side, to make the magnetic material.
The CR80 cards were fairly cheap to make, the ones using the self adhesive material are a bit more expensive as you need to buy plastic sheet and lose quite a fraction of the sheet when cutting the cards out and then there's the cost of the magnetic strip. It looks do-able, though, and probably worth it if the original cards aren't available any more.

https://youtu.be/0ofbcMNU2Zk
https://youtu.be/1NByD6thetA

Andrew

John Garza (3665) · 07-03-2023, 09:13 PM

Andrew,

I've seen and was amazed at your work on the Casio! Seriously, you are the only man to ever make me want to buy a Casio.

I have an HP-9100B in need of mag cards. I have a stock of 9800 series cards that are the same thickness and width - just longer. And they work fine in the 9100 and the extra length gives you more of a 'handle'.

I have tried mag cards from IBM typewriters cut down to size. These are Hollerith-sized (as in punch cards). Evidently they reused the media mechanical design from the punch card days. At any rate, they do not work and I'm not sure why. The first program step always reads back in as a 77 (return), regardless of what code was written. I have tried this with 2 cards I made and I get the same error.

The 9800 cards work flawlessly. And both are 0.2mm thick.
Could there be some difference in the magnetic properties of the media itself?

-J

blackjetrock · 07-03-2023, 09:36 PM

(07-03-2023 09:13 PM)John Garza (3665) Wrote: Andrew,

I've seen and was amazed at your work on the Casio! Seriously, you are the only man to ever make me want to buy a Casio.

Some of the older Casios are really nice, The FX201P/202P sort of models. Some of them not so nice.

Quote:I have an HP-9100B in need of mag cards. I have a stock of 9800 series cards that are the same thickness and width - just longer. And they work fine in the 9100 and the extra length gives you more of a 'handle'.

I've just had a search and see what you mean. Similar but longer. I haven't seen any photos of the magnetic side, I assume they are totally covered in magnetic media material?

Quote:I have tried mag cards from IBM typewriters cut down to size. These are Hollerith-sized (as in punch cards). Evidently they reused the media mechanical design from the punch card days. At any rate, they do not work and I'm not sure why. The first program step always reads back in as a 77 (return), regardless of what code was written. I have tried this with 2 cards I made and I get the same error.

The 9800 cards work flawlessly. And both are 0.2mm thick.
Could there be some difference in the magnetic properties of the media itself?

-J

It's possible that the typewriter cards are Hi-Co and so can't be written by the Lo-Co writer. If you can find some backing material that is 0.2mm or slightly less then you'd be able to put some self adhesive lo-co tape on and try that. PM me if you'd like to try.

Andrew

brouhaha · 07-04-2023, 01:09 AM

(07-03-2023 06:35 PM)John Garza (3665) Wrote: Does anyone have a source for the mag cards for the older HP desktop machines?
Or perhaps compatible magnetic media that can be cut to size?

I have a reel of two-inch video tape. I think gluing strips of it to card stock or think plastic sheet stock might work. IIRC, two inches is the right width for the 9100.

blackjetrock · 07-04-2023, 03:09 AM

(07-04-2023 01:09 AM)brouhaha Wrote:
(07-03-2023 06:35 PM)John Garza (3665) Wrote: Does anyone have a source for the mag cards for the older HP desktop machines?
Or perhaps compatible magnetic media that can be cut to size?

I have a reel of two-inch video tape. I think gluing strips of it to card stock or think plastic sheet stock might work. IIRC, two inches is the right width for the 9100.

What sort of glue do you use to secure the tape to the backing?

Andrew

brouhaha · 07-04-2023, 07:09 AM

(07-04-2023 03:09 AM)blackjetrock Wrote: What sort of glue do you use to secure the tape to the backing?

I have no idea. Experimentation is probably required.

johnb · 07-05-2023, 03:26 PM

Just out of pure curiosity, I'm guessing Hi-Co and Lo-Co are abbreviations for "High Coercivity" and "Low Coercivity"?

Educate me! Why two different kinds of media? Advantages / disadvantages, and so on...

blackjetrock · 07-05-2023, 06:14 PM

(07-05-2023 03:26 PM)johnb Wrote: Just out of pure curiosity, I'm guessing Hi-Co and Lo-Co are abbreviations for "High Coercivity" and "Low Coercivity"?

Educate me! Why two different kinds of media? Advantages / disadvantages, and so on...

Yes, high coercivity and low coercivity.

Coercivity is a measure of how hard it is to magnetise the material. It's what H is needed to magnetise, on the B-H curve. If you want to make something that isn't going to be re-recorded like an ID badge then you'd use Hi-Co as it will be recorded in a special Hi-Co writer. It is then more robust to stray magnetic fields. Lo-co material is used when you will be re-recording data, like calculator storage cards. As the H of the BH is generated by electric current, hi-co writers need more power than lo-co to reach the required H. So in battery powered equipment you'd use lo-co to reduce the power requirement.

Andrew

johnb · 07-05-2023, 09:17 PM

(07-05-2023 06:14 PM)blackjetrock Wrote: If you want to make something that isn't going to be re-recorded like an ID badge then you'd use Hi-Co as it will be recorded in a special Hi-Co writer. It is then more robust to stray magnetic fields. [emphasis mine]
[...]
Lo-co material is used when you will be re-recording data, like calculator storage cards.
[...]
So in battery powered equipment you'd use lo-co to reduce the power requirement.

Well duhhhhh!

I really should have been able to figure that out for myself.
And I'm embarrassed that I did not.
Thanks for humoring me, though!

[JB, here donning the dunce cap for today, LOL...]

johnb · 07-05-2023, 09:27 PM

Just had a thought... magnetic coercivity is one of those parameters that you have to be careful to remember the mathematical definition, not the English one.

Because "high coercivity" here means "more resistant to coercion" (or "requires more coercian for the same amount of change in residual magnetism").

Whereas a naïve interpretation based only on language might lead you up the garden path of thinking "high coercivity" means "more easily coerced."

blackjetrock · 07-06-2023, 01:16 AM

(07-05-2023 09:27 PM)johnb Wrote: Just had a thought... magnetic coercivity is one of those parameters that you have to be careful to remember the mathematical definition, not the English one.

Because "high coercivity" here means "more resistant to coercion" (or "requires more coercian for the same amount of change in residual magnetism").

Whereas a naïve interpretation based only on language might lead you up the garden path of thinking "high coercivity" means "more easily coerced."

Yes, I never thought of it like that, but then I used to work on machines that measured coercivity, so I'm more familiar with the concept.

Andrew

johnb · 07-06-2023, 01:50 PM

(07-06-2023 01:16 AM)blackjetrock Wrote: Yes, I never thought of it like that, but then I used to work on machines that measured coercivity, so I'm more familiar with the concept.

Yep, I know what you mean!

I've been a science geek as long as I can remember. Since about age 5 I knew I would be a scientist or an engineer -- or maybe an astronaut -- it was merely a question of figuring out which one I would stick with as a career, LOL.

And even with that, I find I forget all sorts of symbols and concepts that I once knew, and some of them I knew well.

"If you don't use it, you lose it!"

LOL... saying that, I'm astonished at how much nuclear physics I've managed to retain, 36 years after leaving the Navy (yup, I was a submarine nuc operator). But still... even though I can remember the 6-factor formula and some others, I doubt I remember correctly which Greek letter represents "Average Logarithmic Energy Decrement," much less how to calculate it. (Betcha there is a log() in there somewhere, haha!) I could check the math of a modern RO for his startup calculations, but I sure couldn't verify the logic was correct.

johnb · 07-06-2023, 01:54 PM

(07-06-2023 01:50 PM)johnb Wrote: LOL... saying that, I'm astonished at how much nuclear physics I've managed to retain, 36 years after leaving the Navy (yup, I was a submarine nuc operator).

Hahaha.... of course, I know why my retention of that particular material is so high.

It was pounded into me at high pressure with the Fear of God and the US Navy behind it.

(I started to say "NAVSEA 08" instead of the US Navy, but probably only another Navy Nuc would know that's the Naval Reactors Division.)

John Ioannidis · 07-08-2023, 01:02 AM

a related problem is how to read old magnetic media when you don't have the original equipment, or when you don't trust the integrity of the medium and its ability to go through the reader mechanism, a common problem with very old magnetic tapes that have been stored in less-than-ideal conditions. Search for "magnetic developer" in your favorite search engine. I still have some Sprague magnetic developer that came in little pressurized spray cans *somewhere*. If/when I find them, I'll "develop" an HP-67 card and post the results.

John Garza (3665) · 07-08-2023, 01:18 AM

(07-08-2023 01:02 AM)John Ioannidis Wrote: If/when I find them, I'll "develop" an HP-67 card and post the results.

I think this was done decades ago by the PPC group. And at the time, while I had no special chemicals, I did have a jar of iron filings from my old chemistry set. Worked just fine - you could see the tracks on the card. Just be very careful cleaning the filings off the card if you want to use it again.

-J

[HP: 9100B/9815A/35/45/55/80/70/65/67/67T/97/97S/91/92/21/22/
27/25C/29C/19C/10/31E/32E/33C/34C/37E/38C/41CX/71B/28S/19BII/
12C/15C/32SII/33S/35S/48GX/50G/Prime/DM32/DM42]
[TI: 50/50A/51A/55/52/56/57/58/58C/59/60/66]

ijabbott · 07-08-2023, 08:31 PM

(07-08-2023 01:02 AM)John Ioannidis Wrote: a related problem is how to read old magnetic media when you don't have the original equipment, or when you don't trust the integrity of the medium and its ability to go through the reader mechanism, a common problem with very old magnetic tapes that have been stored in less-than-ideal conditions. Search for "magnetic developer" in your favorite search engine. I still have some Sprague magnetic developer that came in little pressurized spray cans *somewhere*. If/when I find them, I'll "develop" an HP-67 card and post the results.

You could also use a magnetic viewer such as Arnold B-1022.