Argon Laser Pulse tester

[Mosc007]

Spent some time sorting out this MAX1771. It pretty much is as bad as what is posted on the net. It suffers badly from noise on the Feedback input. When their is noise it just doesn't work. Also, Boosting from 12 Volts up to 400 Volts is pushing it a bit with this Boost chip. It seems quite a capable boost IC for low voltage but High Energy pulses at High Voltage cause problems with it.

Anyway, I changed the layout slightly. I had a very long track on the Feedback pin to the voltage divider. I shortened it as much as possible and put the second voltage divider resistor directly at the Feedback Pin. That made a big difference. It was now stable from 100 Volts to about 300 Volts. Next I put a 220 pF Cap on the Feedback pin. It's now quite acceptable. Very good regulation from 100 Volts to about 200 Volts. Still good from 200 volts to 350 Volts. Around 400 Volts it is slightly unstable. The Voltage fluctuates about 10 Volts. No Drama for the purpose of this boost circuit.

I am now happy with the 12 Volt to 100-400 Volt Boost circuit. Next I will build the Ignitor circuit. Have the bits. Will be basicaly based on the original Uniphase Igniter. Except will be manual trigger of the SCR from the 12 Volt supply.

 

[Mosc007]

I have been a bit slack lately. Havn't done much more on it. After trying several Toroids for the ignitor transformer I can't get enough output voltage. It appears I need exactly the same permeability in the Toroid as the original for the tuned circuit to work correctly.

I will just use one of the ignitor boards from the few dead tubes I have here.