Hi everybody,
I got some of these russian tubes from the net, they are NOS and tested very good with my tube testers (using 12ax7 settings, heater control lowered at 6.3V).
Now, they are on my desk since one week, I'm still awaiting for those 9pin socket saver adapters.. and I was curious to hear one of them in my small AA3 amp.
I did the maths (35+50+6=91 120-91=29 29/.150=193), replaced this big 10 watts resistor, turned the amp ON and ... the 6N2P filaments don't lit! What am I doing wrong?
Is this because of the 6N2P filaments, since they are hooked in parallel inside the tube. Or maybe I did the maths wrong.. This amp works very well with a 12ax7...
Here's how everything's hooked:
Thanks!
I got some of these russian tubes from the net, they are NOS and tested very good with my tube testers (using 12ax7 settings, heater control lowered at 6.3V).
Now, they are on my desk since one week, I'm still awaiting for those 9pin socket saver adapters.. and I was curious to hear one of them in my small AA3 amp.
I did the maths (35+50+6=91 120-91=29 29/.150=193), replaced this big 10 watts resistor, turned the amp ON and ... the 6N2P filaments don't lit! What am I doing wrong?
Is this because of the 6N2P filaments, since they are hooked in parallel inside the tube. Or maybe I did the maths wrong.. This amp works very well with a 12ax7...
Here's how everything's hooked:
Thanks!
No, the currents don't add, they will all be the same. You need a 12ax7 in that string, using its 12.6v 150mA connection, pins 4&5.
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Well, demonzotov was on the right track but still wrong.
You can't mix different heater current requirements in a series string. The 35W4 and 50C5 are 150mA heaters, and the 6N2P is 300mA.
Simplest solution is to go back to a 12AX7 and wire it for 150mA in the string. Or else you need to devise some other configuration, such as with a transformer.
EDIT: Oops, jgf beat me to it.
You can't mix different heater current requirements in a series string. The 35W4 and 50C5 are 150mA heaters, and the 6N2P is 300mA.
Simplest solution is to go back to a 12AX7 and wire it for 150mA in the string. Or else you need to devise some other configuration, such as with a transformer.
EDIT: Oops, jgf beat me to it.
Ohh my... thanks for the answer! I misunderstood something here
I didn't realize that all tubes "must have" the same current requirement in a serie circuit and that I can't mix them. I did some research and found a good tutorial explaining current seen by lights of different watt hooked in serie.. Now I see why the heaters were not able to get the required current! Sorry still in a learning process 😱 hope I didn't damage the 6n2p
You could series balance current by putting a resistor in parallel with each seperate filament, however the total power demand will go up and your filament supply might not be rated high enough. The other issue is that a filament changes charatceristics when warming up so for that first second or so its going to be all over the place!