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I put everything back the way it was. If I bias the output tube with
-56v I get a current of 36ma and, with the plate at 390 or so, I get
a dissipation of 14w. So I'm ok. I could also achieve this with cathode
bias by changing the current 470 ohm cathode resistor to 600 ohms,
which I don't have right now. This with the 5Y3GT.
I also changed the screen resistor to 4.7K and that dropped the screen
voltage to 380v.
The amp sounds pretty good like this so I'm going to leave it for now and
go on to phase 2 in which I'll add the second channel preamp and effects.
The numbers as they now stand :
With 5Y3GT :
...On standby :
-56v I get a current of 36ma and, with the plate at 390 or so, I get
a dissipation of 14w. So I'm ok. I could also achieve this with cathode
bias by changing the current 470 ohm cathode resistor to 600 ohms,
which I don't have right now. This with the 5Y3GT.
I also changed the screen resistor to 4.7K and that dropped the screen
voltage to 380v.
The amp sounds pretty good like this so I'm going to leave it for now and
go on to phase 2 in which I'll add the second channel preamp and effects.
The numbers as they now stand :
With 5Y3GT :
...On standby :
AC mains.......... 120 vac
PT secondary ..... 331-0-331 vac
B+ first filter... 440 vdc
...Off standby :PT secondary ..... 331-0-331 vac
B+ first filter... 440 vdc
B+ 1st filter cap. 393 vdc, 1.3 mvac
6v6 at plate ..... 389 vdc
screen node ...... 393 vdc
6v6 at screen .... 380 vdc (4.7K screen resistor)
preamp node ...... 305 vdc
V1a,b at plate.... 202, 204 vdc
6v6 cathode current at idle :
Paul P
6v6 at plate ..... 389 vdc
screen node ...... 393 vdc
6v6 at screen .... 380 vdc (4.7K screen resistor)
preamp node ...... 305 vdc
V1a,b at plate.... 202, 204 vdc
6v6 cathode current at idle :
fixed -56v bias .. 36 ma
6v6 dissipation at idle...... 14 w
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