• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

My small tube does it work?

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Hello,help me please
I just finish assembly EL34 PP (Assembly kit) but I have question why 12AX7 tube the heater have't a light?

Compare with 6N3 buffer tube it has.

I connect 6.3V to EL34 and 12AX7. > 4 lines (Current 2A/line)

Thank you
 

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Disabled Account
Joined 2010
Hello,help me please
I just finish assembly EL34 PP (Assembly kit) but I have question why 12AX7 tube the heater have't a light?

Compare with 6N3 buffer tube it has.

I connect 6.3V to EL34 and 12AX7. > 4 lines (Current 2A/line)

Thank you

Hi,

If you have a look at this link it's a PDF. The 12AX7 has two heaters if they are wired in series then thats 12V they are 6.3v each.

So at a first guess you have them in series and they should be in parallel for 6.3V.

Link:
http://www.r-type.org/pdfs/12ax7.pdf

If you are not sure then join pins 4 and 5 togeather and put the heater supply across 4-5 and 9

Regards
M. Gregg
 
Last edited:
Hi,

If you have a look at this link it's a PDF. The 12AX7 has two heaters if they are wired in series then thats 12V they are 6.3v each.

So at a first guess you have them in series and they should be in parallel for 6.3V.

Link:
http://www.r-type.org/pdfs/12ax7.pdf

If you are not sure then join pins 4 and 5 togeather and put the heater supply across 4-5 and 9

Regards
M. Gregg

Hi, Gregg.
Thank you for you quoted, I'm recheck again. I connected joint 4,5 to 6.3V and joint 9 connected to ground.:)
 
Disabled Account
Joined 2010
Hi, Gregg.
Thank you for you quoted, I'm recheck again. I connected joint 4,5 to 6.3V and joint 9 connected to ground.:)

Why have you connected pin 9 to gnd?
This can cause problems with heater to cathode leakage.

Pin 9 is one side of the heater pins 4-5 are the other.
Don't use pin 9 to hum buck.

Use some 220 ohm resistors from each side of the heater supply to Gnd.

Regards
M. Gregg
 
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