• 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.

6N3/6N6 headphone amp using PCB.

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Ryssen

Ryssen

Member
Joined 2003
I did some shifting of the ECC99 and 6N6P,and I must say that I´m stuck on ECC99.
So I tried to lower the voltage and at 270v one channel dropped out and the other started
distorting.
So I want the other way and turned the voltage up and att 305 volt after the 1rst resistor it was like the amp came alive...I could play much louder and better sound...
Whats a man to do??
 
J

JoeAlders

Member
Joined 2011
"So I tried to lower the voltage and at 270v one channel dropped out and the other started"

But that is perhaps to expect when one lowers the supply voltage and as a consequence lowers the plate to cathode voltage of the triode. You have to figure out (using LTspice) again what biasing is needed to get that triode operating within its working grid bias (sorry perhaps I do not use the correct words "working grid bias" but the English tongue part of our Forum can correct me here).
 
Ryssen

Ryssen

Member
Joined 2003
In this data sheet for ECC99 it says that it can take 5w,is that per section or the whole tube?

attachment.php
 

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J

JoeAlders

Member
Joined 2011
Ryssen said:
How do I calculate the dissipation of the tube (not LT spice..)
I have 2,26v over the 82 ohms katodresistor
Click to expand...


You have to measure (no signal at input):
1. power supply voltage Vs.
2. DC voltage across plate resistor VRp.
3. DC voltage across Cathode resistor VRk (= 2.26V)
4. Calculate plate voltage Vp=Vs - VRp - VRk

5. Calculate the DC plate current through the tube:
Ip=(VRk/Rk) In your case : 27.6 mA
6. Calculate Plate Dissipation:


Pd = Vp x Ip (Watt)


Or measure simply the DC voltage across plate and cathode and then multiply this by Ip(=27.6 mA)
 
Ryssen

Ryssen

Member
Joined 2003
Or measure simply the DC voltage across plate and cathode and then multiply this by Ip(=27.6 mA)
Click to expand...
I took the simplest road,for me.. 3,97w a peace,a little to high then.
It seems that I should go down to (like you have done Joe Alders))150v or under but then the sound dissaperes.I will try again and go to 150 or under and see what happends.
 
Ryssen

Ryssen

Member
Joined 2003
I adjusted the voltage down to about 230v.One channel played one is silent.When i touched the pin 7 grid with the DMM probe it starts to play.....its playing yet,strange.
But now i have a powerdissipation of 3,92w/tube.
Yes I will add another 100 ohm to the 82 ohm so that I can bring the voltage up.
 
kodabmx

kodabmx

Member
Joined 2011
Then you have a bad part or solder joint somewhere. Both channels should operate identically. Pin 7 is a grid, I suspect a bad grid leak resistor from pin 7 to ground (or to the plate of the bottom tube depending on which triode is "on the top" - pins 123 or 678). Connecting your DMM gave the grid a 10M path to discharge - it's so negative, it cuts off the tube.
 
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kodabmx

kodabmx

Member
Joined 2011
Ryssen said:
Hmmm bad part I have the 182 ohms catodresistors now.On one channel I get 3,24v and the other 0.8v.And if I change channel on the tube It follows could one tube be faulty?
Click to expand...

If you swap the tube and the problem follows the tube, it's the tube. I would say the one with 0.8V is worn out or defective, but the fact it worked when you touched pin 7 tells me the problem is between that pin and whatever it's connected to. Which tube is on the channel that isn't working properly? 3.24V or 0.8V?
 
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