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6C4C E80CC PP IT coupled
6C4C E80CC PP IT coupled
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Old 5th December 2017, 11:25 AM   #31
jazbo8 is offline jazbo8
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6C4C E80CC PP IT coupled
Updated schematic:

Screenshot - 12_5_2017 , 1_28_10 PM.png
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Old 6th December 2017, 07:21 AM   #32
6A3sUMMER is offline 6A3sUMMER  United States
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I am still trying to understand the circuit of L1, R10, C4, and R9.

I would think a circuit of bias rectifier, and low pass filter consisting of capacitor, choke, capacitor, and resistor to ground (or potentiometer to ground to make the bias voltage adjustable) would be enough to give bias to the grids through the secondary center tap, and to return the grid bias supply to ground.
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Old 6th April 2018, 09:44 AM   #33
claudiomas is offline claudiomas  France
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you see in "post 7" attached schematics rectifier go to choke "parallel" to grd not trought "serie"
zoom attached
my choke its afther rectifier and filter its here for improve 6C4C stability and performances
like grid choke
this avoid grid current and improve stability and sound
this its wath i tink but i've not the teoretical knowlege to prove it
thats way i usually do not post schematics, i do becose somebody ask for.
like many poor people think
Master Sakuma San its ignorant nonsense amp builder
i do amplifier like artist make music and i have little teoretical knowlege.
you see i do not pretend to teach nothing i just like nice tube amps
Attached Images
File Type: jpg post 7.jpg (59.6 KB, 90 views)
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Last edited by claudiomas; 6th April 2018 at 09:47 AM.
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Old 6th April 2018, 11:54 AM   #34
6A3sUMMER is offline 6A3sUMMER  United States
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claudiomas,

On post #33 you zoomed in to show the bias supply rectifier and the bias supply filter choke.

On the schematic on post #7, look at the Other choke:
“self BF 100 Ohm choke” and the 20uf capacitor
that connects to the secondaries of the interstage transformer
which drives the two 4Y25 tube control grids.

You will notice that one end of the self BF 100 Ohm choke connects to the
negative bias supply, and the other end connects to the junction of the two interstage secondaries plus the top of the 20uF cap.
The 'bottom' end of the 20uf cap connects to ground.
Neither end of the self BF 100 Ohm choke is connected to ground in post #7.

Your schematics show the choke and cap both going to ground at the interstage secondaries (including the schematics that have a 1k Ohm resistor in series with the choke).
Those are not connected the same as the schematic in post #7.

Last edited by 6A3sUMMER; 6th April 2018 at 11:58 AM.
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Old 6th April 2018, 01:53 PM   #35
claudiomas is offline claudiomas  France
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grids flow to ground by choke this its the goal
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File Type: jpg grid bias.jpg (172.4 KB, 71 views)
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Last edited by claudiomas; 6th April 2018 at 02:01 PM.
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Old 7th April 2018, 09:14 AM   #36
6A3sUMMER is offline 6A3sUMMER  United States
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Not only the grid 'flows' to ground through the choke, the - Bias flows to ground through the choke.

You have -57V bias, and 10mA current marked on some schematics.
With 10mA and -57V bias, that would be:
57V/0.01A, that requires 5,700 Ohms of DCR in the choke.
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