Author Topic: EEVblog #1169 - TI 1972 Computer Interfacing  (Read 3787 times)

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Offline GeorgeOfTheJungle

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #50 on: January 20, 2019, 03:01:42 am »
The 3M Whisper Writer was a portable modem+terminal with a thermal printer (the printer was a trendcom 200 ~= Apple Silentype).

https://duckduckgo.com/?q=3M+Whisper+Writer&atb=v134-6__&iax=images&ia=images


« Last Edit: January 20, 2019, 03:06:10 am by GeorgeOfTheJungle »
int main (void) { while (1) fork(); }
 

Offline texaspyro

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #51 on: January 20, 2019, 05:50:37 am »
Quote
The [Toshiba T-1000] battery is just 4 NiCad cells in an open-frame plastic holder...  trivial to rebuild.
Doesn't it have some sort of "Sense" terminal as well?  (I'm pretty sure I've lost the actual pack.)  I was disappointed that it failed to run with no battery installed :-(
I would've mailed it to Dave for a tear-down, if it was such an expensive PITA to mail things internationally from the US.  :-(

I just had a pack rebuilt a few months ago.   I seem to remember there are two red and two black wires in parallel going to a 4 pin connector.
 

Online helius

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #52 on: January 20, 2019, 06:27:44 am »
NiCd chemistry is very rugged and doesn't need balance sensing, it can just be float charged indefinitely and sheds the excess energy as heat. This is one reason why simple substitution of NiMH cells in older devices doesn't work.
Sometimes the reason the machine won't run without batteries is that it also uses them to rectify the power input (I think certain HP calculators worked this way).
 

Offline texaspyro

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #53 on: January 20, 2019, 07:44:08 am »
If the old NiCd charger circuit was a trickle charger, you can often substitute NiMH cells.  A 0.1C charger for 1500 mAh NiCd cells works out to a 0.03C 4500 mAh NiMH charger.  Most NiMH cells will tolerate C/30 trickle charging just fine.
 

Offline German_EE

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #54 on: January 20, 2019, 08:38:32 pm »
"Ahh the VT52, great device, and one of the best keyboards ever.  The keyclick was generated by a big relay that just clunked closed when you typed. "

A BIG THANK YOU to user Boffin for this idea. I just tried it and it works remarkably well
Should you find yourself in a chronically leaking boat, energy devoted to changing vessels is likely to be more productive than energy devoted to patching leaks.

Warren Buffett
 

Online bsfeechannel

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #55 on: February 24, 2019, 08:51:11 am »
The solenoid, as it was called, was added for touch typists accustomed to the sound of the printer head. It could be enabled or disabled on the fly as this IBM 3278 demo shows. The solenoid basically hammered the casing of the keyboard which was built like a tank.

« Last Edit: February 24, 2019, 08:55:40 am by bsfeechannel »
 


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