[madghost]

I obtained a Heathkit tube tester model IT-17. I wanted to test my Philco 41-290 tubes but the tube chart on the tube tester does not include the ones Philco uses (it has only a few of the item 7 series tubes). I tried to find a tube conversion chart that would allow me to substitue the item number for the actual tube. In other words, if I find a substitute tube number for a 7C6 on the chart, can I use the tube nomenclature of a sub to test my 7C6? Also, I have been trying to find a satisfactory tube conversion/substitution chart on the Internet, but so far no real luck in getting a complete and full listing. Any help in either of these two items would help greatly.
Thanks much!