adding Option 001 (6th digit) to HP 5221B

[av500]

recently acquired a HP 5221B and now added the 6th digit to it (Option 001). Nixie tube courtesy of a German eBay vendor that had a tube for sale right at the day that the counter arrived HP 1820-0092 and HP 1820-0019 ICs for reasonable money from a surplus vendor. The 1820-0016 is $$$, so kludged in a 74LS75, wiring up only the 4 bits to the nixie driver, not the inverted bits to the printer interface. the 7475 has an inverted polarity latch pin, so I added a 2N3904 with 10k base, 10k pullup to invert the latch signal
 

[tv84]

 

[Cubdriver]

Very nicely done!!

-Pat

[dgminala]

Thanks for the post.  Where did you get the 1820-0092 from, and what did they cost?  I'm trying to help a friend repair an HP 5216A counter with a bad driver IC.

Thanks for the help
Dave M

[coromonadalix]

 

[av500]

I ordered two of them for $10 each from https://dsmcz.com/ but they might have been the last ones, since they are not listed  any more