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Old 23rd August 2011, 03:09 PM   #1
vrs007 is offline vrs007  Thailand
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Smile My small tube does it work?

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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File Type: jpg 6N3 buffer.JPG (192.0 KB, 189 views)
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Old 23rd August 2011, 03:48 PM   #2
M Gregg is offline M Gregg  United Kingdom
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Quote:
Originally Posted by vrs007 View Post
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
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Last edited by M Gregg; 23rd August 2011 at 04:11 PM.
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Old 23rd August 2011, 04:39 PM   #3
vrs007 is offline vrs007  Thailand
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Quote:
Originally Posted by M Gregg View Post
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.
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Old 23rd August 2011, 04:49 PM   #4
M Gregg is offline M Gregg  United Kingdom
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Quote:
Originally Posted by vrs007 View Post
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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Old 24th August 2011, 12:51 AM   #5
kevinkr is offline kevinkr  United States
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Actually pins 4&5 should be connected together to one side of the 6.3V supply and pin 9 to the other..

Hopefully your filament supply does not use the chassis for the filament return. Good ingredient for hum if you are doing this..
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Old 24th August 2011, 01:27 AM   #6
vrs007 is offline vrs007  Thailand
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Why have you connected pin 9 to gnd?
> I bought the kit from someone and him recommend me to do that. so I connected pin 9 to chassis ground.
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Old 30th August 2011, 03:59 PM   #7
vrs007 is offline vrs007  Thailand
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I correct it to connect pin 4,5-9 it worked!,
Thank you all.
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Old 30th August 2011, 04:12 PM   #8
kevinkr is offline kevinkr  United States
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Good news!
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