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Thanks! Actually, removing ATTiny2313 chip and then applying 9V voltage to the whole setup (Timer chip works up to 15V but I wonder if that's a bit too much for 2N3904 or the one that I replaced it with, 2N4401), I could get up to 1900V from HV/TP1 with this same config, but that was quite scary! I ...

As a follow-up to the other thread , just wanted to mention that I've succeeded running Geiger Kit at 1300+ voltage. In this modification, I've done the following changes: 1) Q1: FJN330F with BUL216: The package is different and leads wouldn't fit into the holes, so it required some ugly soldering. ...

Hi Jeff, thank you for your answer. Speaking of TO-220, do you think BUL-216 would be a good replacement for FJN3303? I can get this on Mouser, but it's pretty expensive, so wanted to be sure. I've never have paid >$2 for a single transistor before. By the way, previously mentioned components arrive...

I have been doing experiments on increasing the voltage: increased L1 to 15mH, reduced R8 to 4.7 Ohm, increased VR1 to 30 Ohm (to have wider range). Open-circuit voltage of TP2 was getting to around 800V. However, to get that, I'd have to start with 600V, for instance, and then turn VR1 to get highe...

Thank you for a quick and detailed response! I actually do require a bit higher voltages because I'm using the kit with LND 7317 and LND 712, both of which run at 500V or more. The second one also requires 10M resistor instead of 4.7M. Actually, it worked for me with 4.7M, but I've read that's not t...

I have been using your Geiger Counter for quite some time, in fact, own 5 of those that I got from Adafruit, two with the case. This kit is just great! I'm preparing to use one of them in a weather station running continuously 24/7. Since I have been testing the kit with different tubes, including t...