Hi guys ,
I'm new in the forum ; this is my first question .
I just got 4 Marconi 6V6 on EBay for my 5E3 , but I don't own a tube tester ... Is there a way That I can use the amp itself to match a good pair of tubes as close to each other as possible ?.... maybe taking readings form cathode to ground or something like that ? ....
Cheers
SUSO
Matching tubes
Moderators: pompeiisneaks, Colossal
Re: Matching tubes
Output transformer shunt method to measure current draw. But, You must fully understand the dangers of this method. It could be lethal.
Re: Matching tubes
becareful if you have a hot bias you can burn the tubes while you are taking readings. Glowing plates can = minutes!!! not months of life on the tubes.
check this site out for how it all works in an easy to understand layout
http://people.cornell.edu/pages/mt24/Am ... _main.html
best of luck!
check this site out for how it all works in an easy to understand layout
http://people.cornell.edu/pages/mt24/Am ... _main.html
best of luck!
My Daughter Build Stone Henge
Re: Matching tubes
The 5E3 is cathode biased. You need a fixed bias amp to have it function as a tube tester.
If you have a fixed bias amp and are disinclined to measure amps flowing across the OT (like I am), you can get to it indirectly by measuring the voltage and dividing it by the resistance of the winding. Amps = Volts/Ohms. This works very nicely, is a bit safer, and puts your crappy meter (read: anything but a Fluke) at considerably less risk of being fried.
If you have a fixed bias amp and are disinclined to measure amps flowing across the OT (like I am), you can get to it indirectly by measuring the voltage and dividing it by the resistance of the winding. Amps = Volts/Ohms. This works very nicely, is a bit safer, and puts your crappy meter (read: anything but a Fluke) at considerably less risk of being fried.
Re: Matching tubes
Hi again ,
I took a couple of readings from each cathode to the ground leg of the cathode resistor . It's a 270 ohm , but it reads 277 ohms.
The voltage drops I read are very close : 17.40 V from one tube and 17.44 V from the other . I guess they are pretty close .
I'm running my plates at 310 V . My cathode current is 17.40/277=0.062mA . Is this to high for this plate voltage ? .
Cheers .
SUSO
I took a couple of readings from each cathode to the ground leg of the cathode resistor . It's a 270 ohm , but it reads 277 ohms.
The voltage drops I read are very close : 17.40 V from one tube and 17.44 V from the other . I guess they are pretty close .
I'm running my plates at 310 V . My cathode current is 17.40/277=0.062mA . Is this to high for this plate voltage ? .
Cheers .
SUSO
Re: Matching tubes
Hi again ,
I took a couple of readings from each cathode to the ground leg of the cathode resistor . It's a 270 ohm , but it reads 277 ohms.
The voltage drops I read are very close : 17.40 V from one tube and 17.44 V from the other . I guess they are pretty close .
I'm running my plates at 310 V . My cathode current is 17.40/277=0.062mA . Is this to high for this plate voltage ? .
Cheers .
SUSO
I took a couple of readings from each cathode to the ground leg of the cathode resistor . It's a 270 ohm , but it reads 277 ohms.
The voltage drops I read are very close : 17.40 V from one tube and 17.44 V from the other . I guess they are pretty close .
I'm running my plates at 310 V . My cathode current is 17.40/277=0.062mA . Is this to high for this plate voltage ? .
Cheers .
SUSO
Re: Matching tubes
Sorry guys for this silly question ... I just realized that I'm dealing with 2 tubes so my Bias is perfectly set.
6v6 max dissipation is 14 W , that means 70% off would be 9.8W, at 310V I should aim at 31mA max.
So my 62 mA divide by 2 tubes hit right in the bull's eye.
6v6 max dissipation is 14 W , that means 70% off would be 9.8W, at 310V I should aim at 31mA max.
So my 62 mA divide by 2 tubes hit right in the bull's eye.