• 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.

Voltage falls off CCS/bias.

Why would heater leakage current take a different path? Why would it never go through the CCS? The heaters are practically grounded, so sit at 0 Vdc. The CCS is being fed with -66 V. So if there any leakage between heater and cathode, why couldn't there be current flowing?

And why you resort to an ad hominem? It reminds me of this thread: 6C33C heater question
I can get small readings in millivolts (up to 500) between H&K when I energize them separately.
 
Is pin 6 (shield) suppose to be attached to ground on 6gk5?
 

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Are u sure it only drops when you plug in 6gk5 with only heater on and B+1 off? I'm surpprised the drop agreed with my sim with 6gk5 fully on.
I wish to expand bit if we're still on heater-cathode leak, when leak (after some heavy usage) occurs the voltage that destroyed the 330x resistors is coming from plate to cathode voltage of a few hundred volts. Not by 6.3v Ac.
So why not remove 330x2 resistor (only hum)?
I've tried the center tap on the filament transformer grounded, not grounded and hooked up exactly as schematic with the same results.
 
That is ground lift resistor. The electrical earth is connected to chassis and electrical ground of amp is connected to earth via a resistor so it's avoid pick up unwanted noise, hum, buzz etc below the difference of two ground potentials.
 
This sim shows that CCS current flow in both grids when B+ is 0 or not connected, regardless of whether a heater leak or not.
So that is considered normal, there is no leakage after all.
I didn't write that the problem was surely caused by heater to cathode leakage. What I did write is that it could be a possible explanation. There is a big difference between the two.

In your post #18 you accused me of never proving a word I say. That is a flagrant lie. And if we only look at this thread, what was there to prove about me writing that heater to cathode leakage could be a possible explanation? Should I have mentioned literature in which this phenomenon is described to prove this possibility?

It is you who didn't prove anything that you wrote in your post #14. You started to use ad hominem arguments, starting in that same post # 14. I assume that it was caused by you being oversensitive for arguments that are not in line with your line of reasoning and/or me pointing out that you didn't get all that TS already wrote and showed (schematic in post #1) before.

About your simulation in post #30: What is the internal resistance of V2 in your simulation? If it is anything more than 0 Ohm, it would be impossible that the grid currents of U1 and U2 are of equal value.

A grid current of 4.7 mA at a voltage difference between cathode and grid of only 50 mV (with the cathode being positive with respect to the grid) seems unlikely to me. I know that grid current already starts from about -1.3 V (with the grid being negative with respect to the cathode) so I know that some grid current surely will flow. But could this grid current really be 4.7 mA at only 50 mV voltage difference?

My apologies to TS for this weird quarrel in your thread. It was my intention to try to help you but when I get attacked like this in public, I will defend myself in public.
 
I didn't write that the problem was surely caused by heater to cathode leakage. What I did write is that it could be a possible explanation. There is a big difference between the two.

In your post #18 you accused me of never proving a word I say. That is a flagrant lie. And if we only look at this thread, what was there to prove about me writing that heater to cathode leakage could be a possible explanation? Should I have mentioned literature in which this phenomenon is described to prove this possibility?

It is you who didn't prove anything that you wrote in your post #14. You started to use ad hominem arguments, starting in that same post # 14. I assume that it was caused by you being oversensitive for arguments that are not in line with your line of reasoning and/or me pointing out that you didn't get all that TS already wrote and showed (schematic in post #1) before.

About your simulation in post #30: What is the internal resistance of V2 in your simulation? If it is anything more than 0 Ohm, it would be impossible that the grid currents of U1 and U2 are of equal value.

A grid current of 4.7 mA at a voltage difference between cathode and grid of only 50 mV (with the cathode being positive with respect to the grid) seems unlikely to me. I know that grid current already starts from about -1.3 V (with the grid being negative with respect to the cathode) so I know that some grid current surely will flow. But could this grid current really be 4.7 mA at only 50 mV voltage difference?

My apologies to TS for this weird quarrel in your thread. It was my intention to try to help you but when I get attacked like this in public, I will defend myself in public.
If I wrote in details I afraid it would be off topic. If you really want an answer like you said you would rather than self defense, ask again nicely. No one is willing to do donkey work just to spoon feed anyone.
 
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Bias is SET once the tube is HEATED up and B+ applied, not before the B+ and filament are stable.
Duh!
Ok guys I apologize for being a bone head!
Yesterday when I started ramping the B+ up the voltages looked real squirly and I quit increasing and started trouble shooting and notice the voltage fall when I added the heaters. Well I ramped up the variac to 122 volts line and Walla everything fell in place! I just started building **** with solid state in them and I'm not edumicated. Thanks for the help it is much appreciated.
OB