Triode operation kitkat6550

[paul webber]

Hi All,thanks for a very interesting read/forum
I need Help! Please!! I am sure some people will have tried triode operation of 6550 valves and i wondered about their experiences.
I have tried insulating the ul taps and using 100ohm 1/4 watt resistors as small fuses to connect the screen grids to the anodes. Due to the highish anode volts i can only do this when ac mains is low so not a good solution.However i thought sound noticably different Surely over 435 volts on screen grid is too high? (6550)
Next was using spare 2.2k screen grid resistors in series with 2.2k existing to reduce ul tap effect.Volt on screen grids nicely lower.(Semi ul/triode?)But does it need ac bypass? and what resistance value is best? Sounds different again.
A net suggestion is to use 5x 6volt zeners bypassed for ac to reduce screen volts to an exact difference to anode volts
Finally a resistance network to give 245/265 screen volts is suggested (bypassed again) but this is very energy consuming so perhaps not ideal?
As you can tell i am just fumbling about so any help tips most welcome.Preferably not a tip to buy a good valve amp book and learn how valves work though, thanks, although that would be a good idea!!
I always fumble in rubber gloves as thats safest.
Thanks one and all,happy valveing to you all Paul

[Richard]

I have tried insulating the ul taps and using 100ohm 1/4 watt resistors as small fuses to connect the screen grids to the anodes. Due to the highish anode volts i can only do this when ac mains is low so not a good solution.However i thought sound noticably different Surely over 435 volts on screen grid is too high? (6550)

Hi Paul,

Carry on enjoying KT88s are ok for 600v across anode and g2. Decent 6550's (such as Svet which are built to replace last 6550A type) are ok for 500v on plate and g2 when connected in triode (see GE6550A data sheet). Remember also that the cathode is running at +40v so that amount can be taken from the measurement at g2 pin.

Rich

[paul webber]

Hi Richard,
I have 3 sets of 6550c,but the now obvious fact that the cathode volts are deductable makes a tidy difference.Thanks and thanks, i must get soldering again regards paul