Thankyou - I will draw out tomorrow !!The L63 triode is in a cathodyne circuit - there should be a 0.1uF coupling cap to each KT66 connecting to the 47k at the anode and cathode of the cathodyne. The 2k2 provides bias to the input grid via the 1Meg grid leak, and the previous stage couples to pin 5 via the 0.05uF.
The 6SJ7 is set up as a simple pentode amplifier, but with cathode going to ground via a bypassed 1k5, and then an unbypassed 100 to which the feedback is connected (as a resistor divider). The screen pin 6 is RC filtered from B+. The suppressor pin 3 is connected to cathode. The input grid comes from the treble pot and has a 220k grid leak to cathode.
Thankyou - I have attempted to draw this out - diag enclosed.The L63 triode is in a cathodyne circuit - there should be a 0.1uF coupling cap to each KT66 connecting to the 47k at the anode and cathode of the cathodyne. The 2k2 provides bias to the input grid via the 1Meg grid leak, and the previous stage couples to pin 5 via the 0.05uF.
The 6SJ7 is set up as a simple pentode amplifier, but with cathode going to ground via a bypassed 1k5, and then an unbypassed 100 to which the feedback is connected (as a resistor divider). The screen pin 6 is RC filtered from B+. The suppressor pin 3 is connected to cathode. The input grid comes from the treble pot and has a 220k grid leak to cathode.
Thankyou - goit it !!!This is most likely the layout of the L63 stage. It's a self-biased "split load" or also called Cathodyne phase inverter, which also acts as the driver for the output stage. The 2.2K resistor provides the self bias voltage by dropping several volts from the cathode, so the junction of the 2.2K resistor, 1M resistor, and 47K resistor sits at something like 3 to 4 volts lower than the cathode. The 1M resistor impresses this voltage onto the grid. Hence it uses its own cathode current to bias itself.
View attachment 1301459
Thankyou !According to your diagram, the 6SJ7 is a pentode voltage amplifier for the power amp. Like this (using the values you provided in your sketch):
View attachment 1301548
I don't yet know what the other tubes do, as you haven't sketched them out yet.
I'm trying to remember your original photos of the units from the other thread. Was there also a balance control on this unit you are tracing out? I thought I remembered three controls on the front, I assume bass, treble, and balance.
The L63 triode is in a cathodyne circuit - there should be a 0.1uF coupling cap to each KT66 connecting to the 47k at the anode and cathode of the cathodyne. The 2k2 provides bias to the input grid via the 1Meg grid leak, and the previous stage couples to pin 5 via the 0.05uF.
The 6SJ7 is set up as a simple pentode amplifier, but with cathode going to ground via a bypassed 1k5, and then an unbypassed 100 to which the feedback is connected (as a resistor divider). The screen pin 6 is RC filtered from B+. The suppressor pin 3 is connected to cathode. The input grid comes from the treble pot and has a 220k grid leak to cathode.
The 6SN7 might be used for the tone controls. Two triodes with the tone controls between them is a fairly typical setup.
I'm trying to remember your original photos of the units from the other thread. Was there also a balance control on this unit you are tracing out? I thought I remembered three controls on the front, I assume bass, treble, and balance.
No balance control