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In the Forum: Melquiades Amplifier
In the Thread: How to test 6C33C?
Post Subject: How to test 6C33C?Posted by Romy the Cat on: 4/2/2006

It is sucks to live with Russians Tubes.  It is particular sucks to live with 6C33C. They are all deferent when they new, they age very ungracefully and differently.

The life with Super Melquiades, where I use 6x6C33C driving individual channels forced me to think traders about the testing the 6C33C as the lost of virility or gain if any of those six tubes could throw the Melq out of it normal performing level.

Over the years, using the BAT VK-60, Lamm ML2 and eventually the different versions of the Melquiades I was thinking about the different ways to test the 6C33C. Usually I did following:

1)  I had a log for each tube monitoring the amount of bias necessary to set the reference current. Since tube age the bias changes.

2)  Monitor the density and gloss of the tubes getter. Since tube age the getter’s appearance changes

3)  Monitor a tube gain by measure the amount of dB (with 1/4dB precision) that a channel outputs in it zone of transparency driver by a reference signal.

It kind of “works” so far but my approach has many major imperfections and points of instability, not to mention that with 6C33C the change in bias “might” means …. nothing. So, I always thought to find a stable and reliable ways to test the 6C33C. What I need is objective ways to measure gain and mutual conductance of each tube’s halfs at different frequencies and under different operation points

The tube testers are not good. Even if I added the 6C33C socket and slightly modify them then are not good for the 6C33C. Fist of all none of then can handle the current demands of this tube. For instance my Hickok TV-2 can run the 6C33C for not more then 55mA at 230V and at this operation the testers is ready to explode. Also, I do not need some kind of result but I need a perfect test result. The tubes testers do not drive the plates with DC (they use rectified but not filtered voltages) and I feel that it make the tubes in the testers and in the amps to behave differently. So, I am thinking now to build a “perfect” 6C33C tube tester that would be very precisely measure the mutual conductance and the tube gain.

It really should not be difficult to build it but I relay would like to avoid burning my fingers if the solution is already exist. Are anyone out there perhaps seen any ready to go testing solution for 6C33C? If not I will build the damn thing…

Romy the Cat

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