Neon bulbs for HP 3420B/419A optical chopper

[perdrix]

After many attempts to get the chopper circuit in the my HP 3420B working correctly using many different neon bulbs, I was sent a few GT-NE6H1925T neon bulbs by George Kerber.

I took two out of the packet at random and installed them in the the optical chopper.  Powered on and was delighted to see the correct waveform at test point TP1 on the A2 board.  I had almost given up on this so am really delighted.  I think the problem was the the neons I had been using previously (e.g. A2B) had too low a strike voltage and were both firing simultaneously.   These have a strike voltage of about 95-100V (depending on how you measure it) and a sustain voltage of about 68V.

A huge thank you to George!

Happy New Year
Dave

[Tony_G]

Awesome - Available right now on Mouser for US$0.44

TonyG