Inside the ZOPAN PFL-22 Frequency Counter... and what Keri found there

It's been a while... and it's new gear at Keritech time - with Nixies! This ZOPAN PFL-22 frequency counter / timer is of 1982 vintage, uses eight Z573M tubes as display devices, and all kinds of other indicators: neon lamps, incandescent bulbs and a LED. Yes, that's right: there's a single LED in a whole device. All its logic is based on TTL gates and counters, some of them higher speed (74Sxx series) and it normally goes up to 100MHz, which I'd like to upgrade to be able to use it for checking local oscillators in FM radios. I decided to go full-on @atkelar on this frequency counter, taking it apart, cleaning the front and back, all the controls and parts... Total discombobulation - and later on, recombobulation! Maybe IC upgrade too, if I get 74Fxx fast gates. Shoving a few nanoseconds off propagation time might do the trick extending the max frequency, but I'll only try it after I get the counter working again. 0:00 Intro 0:57 A Look at the Counter 4:10 Testing 13:00 Back Panel 16