The spare IR53HD420 chip is... well also fried. This time I re-soldered the whole circuit (not that I found anything wrong with the old one) for making sure I haven't missed something. Got a new 10R resistor for diode bridge protection (and as it turns out works like a fuse as well) and started with a test with dummy load of 200K resistors. All went well for a while. There was voltage in output and there were no smoke :)

When I tried to connect UV lamp for about 5 seconds it turned on and for the first time actually emitted UV light, but then the 10R resistor burned and ballast turned off. This did not seam like a big problem. After several days I got a higher wattage resistor and soldered that in and then the ballast IC blew up again ;(

It did not even light up the lamp, it just blew up. This does not make sense anymore, but I will not give up. I have a idea and a plan :)

I used this schematic for a reference, it is almost the same as mine, but I use slightly different IC and I have connected only one lamp. I found the circuit here:

http://ivan.bmstu.ru/avia_site/r_main/HWR/Others/EPRA_220/l.html

If anyone has any ideas feel free to leave comments :)