Making new HP-65/TI 59 magnetic cards out of VHS tape

[voltaage]

Hello.

I just got a new TI 59 calculator from a flea maket. It came with all the master library cards as well as for an extra batch of blanks. Apart from the problems I'm facing with the power supply module, I'm curious if I can make new cards from scratch. So I thought this would be logical to do:

I've also bought a NOS VHS cassette from that market too, it is branded Sony T-120PR. I don't have any cassette players nor cassettes themselves, so I think is reasonable to sacrifice this one for making new cards for use in calculators. That's for the magnetic side. For the info side I picked thin acetate sheets. This is becasue it would glide easily into the pressure plate and also it will provide durability for several reads. I'll maybe pick some soft glue stick to join the two things together, after all, the tape is not that heavy. Of course for straight cuts I'll use a small guillotine for best results.

I haven't tested those cards because my TI is still under repair. My only concern right now is about the media density. VHS tapes have enought tpi in order to fit 240 lines per picture diagonally. In the case of my cards they should be able to fit 480 bytes across. They should work according to my logic, especially because the cassette tape is "professional" according to the label.

Have you tried to do this before with TI's/HP-65 cards?

[ijabbott]

It will depend on how similar the magnetic properties of the VHS tape coating are to those of the magnetic card coating.

[Garth Wilson]

I would fasten the tape with double-sided adhesive tape. Regardless, I expect you'd probably foresee and avoid any dangers of doing damage, and you won't run out of tape or material in your experiments.

[KimH]

I am not 100% sure how the 65/67 works, but I do know that the cards for the 75C & 71B has a SYNC/TIMING track which is written in the production.

From the HP Journal

(11-03-2021 07:43 PM)voltaage Wrote:  Hello.

I just got a new TI 59 calculator from a flea maket. It came with all the master library cards as well as for an extra batch of blanks. Apart from the problems I'm facing with the power supply module, I'm curious if I can make new cards from scratch. So I thought this would be logical to do:

I've also bought a NOS VHS cassette from that market too, it is branded Sony T-120PR. I don't have any cassette players nor cassettes themselves, so I think is reasonable to sacrifice this one for making new cards for use in calculators. That's for the magnetic side. For the info side I picked thin acetate sheets. This is becasue it would glide easily into the pressure plate and also it will provide durability for several reads. I'll maybe pick some soft glue stick to join the two things together, after all, the tape is not that heavy. Of course for straight cuts I'll use a small guillotine for best results.

I haven't tested those cards because my TI is still under repair. My only concern right now is about the media density. VHS tapes have enought tpi in order to fit 240 lines per picture diagonally. In the case of my cards they should be able to fit 480 bytes across. They should work according to my logic, especially because the cassette tape is "professional" according to the label.

Have you tried to do this before with TI's/HP-65 cards?

[Massimo Gnerucci]

(11-04-2021 12:33 PM)KimH Wrote:  I am not 100% sure how the 65/67 works, but I do know that the cards for the 75C & 71B has a SYNC/TIMING track which is written in the production.

Yes, since they are hand pulled.
Those motor driven don't have that marking.

See Fig. 8 on page 7.

(Modified to add reference)

[Dave Frederickson]

(11-04-2021 12:33 PM)KimH Wrote:  I am not 100% sure how the 65/67 works, but I do know that the cards for the 75C & 71B has a SYNC/TIMING track which is written in the production.

The 71/75 cards are hand-pulled - not a very precise speed, so a timing track is required. All other HP card readers use a speed-controlled motor, so a timing track isn't necessary.

As a side note, mag cards can be degaussed to wipe any stray magnetic data. This, however, should NOT be done to the hand-pulled cards as it will destroy the timing track.

[voltaage]

(11-04-2021 04:36 AM)Garth Wilson Wrote:  I would fasten the tape with double-sided adhesive tape.

Yes. Indeed double sided tape can be very useful here since it's uniform. I just made 2 "new" cards using glue stick. Turns out that, even after 2 hours of drying, it leaves a bit of a rough surface on the magnetic side. That could be dangerous for the recording head since it might tear down the tape. I would need something like art adhesive spray to make an uniform /and thin) layer of glue, since the thin magnetic VHS tape can reflect inperfections.

(11-04-2021 04:36 AM)Garth Wilson Wrote:  Regardless, I expect you'd probably foresee and avoid any dangers of doing damage, and you won't run out of tape or material in your experiments.

Of course I'll do extensive testing in order to see the performance of the magnetic side; this of course not with the original card mechanism, maybe with some of the dead cassette recorder heads I have around. At the slightest detail here, I will stop the experiment to avoid damaging the mechanism.

[voltaage]

(11-04-2021 12:57 PM)Dave Frederickson Wrote:  

(11-04-2021 12:33 PM)KimH Wrote:  I am not 100% sure how the 65/67 works, but I do know that the cards for the 75C & 71B has a SYNC/TIMING track which is written in the production.

The 71/75 cards are hand-pulled - not a very precise speed, so a timing track is required. All other HP card readers use a speed-controlled motor, so a timing track isn't necessary.

As a side note, mag cards can be degaussed to wipe any stray magnetic data. This, however, should NOT be done to the hand-pulled cards as it will destroy the timing track.

Well that is unfortunate. I wonder that might be frustrating for HP 71/75 users. All of your cards need to be in excellent condition in order to be used.

I'm aware of other hand-pulled card mechanisms that incorporate an opto-mechanical encoder (just like oldschool ball mouses) which basically elliminates the need of pre-recorded media.

[Dave Frederickson]

(11-04-2021 05:59 PM)voltaage Wrote:  

(11-04-2021 12:57 PM)Dave Frederickson Wrote:  The 71/75 cards are hand-pulled - not a very precise speed, so a timing track is required. All other HP card readers use a speed-controlled motor, so a timing track isn't necessary.

As a side note, mag cards can be degaussed to wipe any stray magnetic data. This, however, should NOT be done to the hand-pulled cards as it will destroy the timing track.

Well that is unfortunate. I wonder that might be frustrating for HP 71/75 users. All of your cards need to be in excellent condition in order to be used.

Sylvain fashioned a jig to hold the cards while cleaning.
https://www.hpmuseum.org/forum/thread-16...#pid139881

[teenix]

It would seem feasible to hand pull a card through the 67 style reader because of the way the data is written on the card. However, you would have to do this at a steady pace so that it is within the timing limits that the hardware expects. Not very practical in real life.

If one was to write different code to fetch the data directly from the card then it should be possible assuming at whatever (reasonable) speed was used, the head can still produce signals at sufficient levels.

cheers

Tony

[ijabbott]

I seem to remember watching a video by HP showing the manufacture of the magnetic cards. Assuming it is not just in my imagination, does anyone have a link?

[Sylvain Cote]

(11-05-2021 10:32 PM)ijabbott Wrote:  I seem to remember watching a video by HP showing the manufacture of the magnetic cards. Assuming it is not just in my imagination, does anyone have a link?

I have never seen a video on this subject, but there is an article in HP Journal June 1983 on the HP-75/71 magnetic card synchro track recording production system. (page 20)

[Dave Frederickson]

(11-06-2021 12:00 AM)Sylvain Cote Wrote:  

(11-05-2021 10:32 PM)ijabbott Wrote:  I seem to remember watching a video by HP showing the manufacture of the magnetic cards. Assuming it is not just in my imagination, does anyone have a link?

I have never seen a video on this subject, but there is an article in HP Journal June 1983 on the HP-75/71 magnetic card synchro track recording production system. (page 20)

I'd like to see the machine in action. It automatically orients the blank cards for recording.

I suspect the machine ended up in Richard's collection and will soon appear on eBay.

[voltaage]

So, a few highlights to conclude:

• The VHS tape is not as wide in order to fit all the card. Therefore you can only write one side per card (not a big deal if you consider they are new).
• The trick for all this to work is that both horizontal sides need to be exactly 0.636 inches and perfectly parallel to each other. Otherwise the card won't detect or would have problems maintaining a constant speed. While lenght might not be as restrictive at 2.9185 in. There is a reason why your Drive Roller Cleaning Card sometimes has some trouble getting to activate the pickup, since this is 0.6175 in (plus the fact this is paper, which is not that strong when trying to push the sensors).
  

So, unless I have a cutting mold precisely manufactured to those dimensions and a quite powerful press, I sadly cannot make new cards.

Wide
Lenght