HP 67 Black Box



#11

Hello,

I have not seen many discussions around here about he HP 67 black box.
I was wondering where I can get one? or How to make one? Do any of you have any schematics of the black box?

thanks in advance,

Fouad


#12

If its a classic "black box", then no one knows what's inside. [;-)

#13

Quote:
I was wondering where I can get one? or How to make one? Do any of you have any schematics of the black box?

The Volume-4 Number-5 (June 1977) issue of "65 Notes" covers it in fair detail on pages 1 and 2, with Lou Cargile's landmark article "Zen And the Art of HP-67 Maintenance" starting on page 4. This might be considered the origin of "synthetic programming" in the user community.

Jake

#14

You'll find the details in the PPC Journal circa 1978/1979. It was a very simple device: a small circuit board was plugged into the power jack on the back of the '67 between the spring plate and the outer two pins. It had a section of the copper removed down its middle and a short cable attached. In the box was a potentiometer (actually, just a variable resistor) and a normally-closed pushbutton in parallel with it.

When the board was inserted, power from the 67's battery had to travel through the box to the rest of its circuitry. By pushing the button, the resistance was added to the battery. IF the resistance was close to zero, nothing happened. If it was large, the '67 saw its power drop to where it turned off while the button was pushed. But if the resistance was just right, the '67 would stop operating *but* its power-on reset circuit wouldn't be triggered.

The result was the 67's registers, being dynamic circuits, would forget their contents but not get reinitialized. This allowed access to making all sorts of non-normalized numbers, exploring around the CPU's address space, etc. Again, check the PPC Journals for the details.

I used this trick to create arbitrary bit patterns in the '67 registers and write them to magnetic cards. By reading them into the then-brand-new HP-41C, the 41's use of memory could be explored, leading to my talk on same at the 1979 Conference in Santa Clara a month after the '41 came out. As I recall, it took about 20,000+ keystrokes that weekend to map out the data for that presentation.

Yes, I agree with others on the quality of early HP calculator keys!


#15

Jake is right - it was before the HP-65 Users Club had been renamed to PPC. My error.

#16

Quote:
As I recall, it took about 20,000+ keystrokes that weekend to map out the data for that presentation.

Yes, I agree with others on the quality of early HP calculator keys!


And the fanatic durability of they key puncher. :)


#17

Thank you - small potatoes compared to the wonderful things others here have done!

But typical of my earlier days, including sitting in Hawaii on the US Air Force's pay in December 1976 working on my HP-67 to explore its use of non-normalized numbers in division as timers, etc. instead of chasing wahinis and drinks. Youth is wasted on the young...


#18

Hello Guys,

Do you know where I can get a copy of the HP-65 Notes Volume-4 Number-5 (June 1977) issue ?

Regards,

Fouad


#19

Great work Jim...I wish I was around the HP golden age.
I know this might surprise some of you but I am only 15 years old who has inherited his father's HP-41CX, since then my eyes have opened to the world of possibilities surrounding HP calculators.

SURPRISE!!

FOUAD


#20

Jake Schwartz has done the herculean job of capturing all the old user journals and such on a set of disks. You'll find them at:

<http://www.pahhc.org/ppccdrom.htm>

The users groups of the past have been supplanted by the Web - something of a loss as the journals were a delight to receive and the mailing sessions at Richard Nelson's home (and later, the PPC Office) were a great gathering of enthusiasts. But we could never have imagined the real-time communications with others around the world, not just the Los Angeles area.

Good old days? Not nearly like the ones we have now!


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