Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: apeontheweb on February 03, 2026, 12:35:42 pm
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Here are two links for the wiring schematic and layout for the 5E3. I have a question about the plate resistor on the phase inverter. V2B is the phase inverter. There is a 56K resistor on the phase inverter plate. In the wiring diagram, I can see a 16mF capacitor in between the 56K resistor and ground. But on the layout, I can see the 56K resistor goes directly to ground. Why is this?
Wiring schematic: https://robrobinette.com/images/Guitar/5E3P_Build/5E3_Schematic_Annotated.gif
Layout: https://robrobinette.com/images/Guitar/5E3P_Build/5E3_Layout._Annotated_Signal.gif
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On the layout, the dotted line is the wire connecting the 56K resistor to the 16uF filter cap, so it all matches up.
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There is a 56K resistor on the phase inverter plate. In the wiring diagram, I can see a 16mF capacitor in between the 56K resistor and ground. But on the layout, I can see the 56K resistor goes directly to ground. Why is this?
I suspect you are looking at the wrong 56K resistor. There are two 56K resistors in the PI circuit and one of them does connect directly to ground as it should. But that's the cathode resistor and the other end connects (indirectly) to the cathode pin 8. The other 56K is properly connected between the plate pin 6 to B+3 node.
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Ok yeah, I was looking at the wrong 56K resistor. I was looking at the one circled in red and I should have looked at the one in blue. (hopefully schematic attaches) Thank you! (http://)