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|1st November 2006, 12:57 PM||#11|
Join Date: Jul 2005
Location: West Virginia panhandle
I offer the following suggestions:
The capacitor at the grid of the 6BH6 is not needed since both sides of it are at ground (DC) potential.
The 2 meg screen resistor on the 6BH6 will need to be changed. The 6BH6 will draw a different screen current than the 6SJ7. Experiment with the value to get a reasonable tube current. I am at work now and I don't have access to a data sheet. The 250 K plate resistor may need reducing also. I just tweak these for the best sound.
I would also reduce the 5 meg grid resistor to 1 meg. Very high value resistors tend to be noisy and drift prone. Any reasonable value resistor will work here.
Again, be prepared to adjust the values of the screen and cathode resistors in the output stage to get a good tube current and a good sound.
Your 6CU6 tube looks like it has seen a bit of use (worn getter). I would keep the plate dissipation down to 8 watts or so since it is the only tube that you have. Sweep tubes tend to be underrated since they run at full power every minute that the TV is on. I have been known to push them beyond the published ratings, but I do this with tubes that are plentiful and cheap.
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|4th November 2006, 01:44 PM||#12|
Join Date: Dec 2005
Thanks Tube_Dude & Thanks Tubelab.com
for your suggestions
I have modified some value...
Now i need draw the load line static and dinamic of endstage tube...
for to determine the correct value of the components.
- Loadline static :
For Anode Current = 0 --> Vak=Vcc (on X axis)
For Voltage Anode = 0 --> Vcc/(Rk+Rdc) (on Y axis)
where Rk = cathode resistor and Rdc = dc resisrance of output trasformer.
My English originates from here
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