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Mike. Watterson · 27th Jul 2019, 9:09 pm

g2, screen grids. The voltage on them sets the gain. They usually connect to 0V / negative/chassis.

Check resistor feeding triode anode of V1. It's a 6C9, or there may be an ECH41 or ECH42 there. You only list one set of Anode and Screen voltages for V1. It's a Triode Hexode.
The triode is the local oscillator and the Hexode g1 is RF in. Its coil is on Anode pin 3 and feed back to triode grid pin 4, internally connected to Hexode. The resistor from the coil to HT is typically 33K, I don't know what it is on the T671. If that resistor goes high resistance the Local Oscillator won't run.

Pin 5 is the Hexode screen grid, to HT via a resistor and typically a 50nF or 100nF decoupler to 0V

The Mica caps are generally fine. They are rectangular and up to 2000pF

It's rarer that paper caps are less than 2000pF, though 1000pF and 470pF are sometimes used.

27th Jul 2019, 9:09 pm	#25
Mike. Watterson Heptode Join Date: Dec 2014 Location: Limerick, Ireland. Posts: 901	Re: Ultra 761. Actually a T671. g2, screen grids. The voltage on them sets the gain. They usually connect to 0V / negative/chassis. Check resistor feeding triode anode of V1. It's a 6C9, or there may be an ECH41 or ECH42 there. You only list one set of Anode and Screen voltages for V1. It's a Triode Hexode. The triode is the local oscillator and the Hexode g1 is RF in. Its coil is on Anode pin 3 and feed back to triode grid pin 4, internally connected to Hexode. The resistor from the coil to HT is typically 33K, I don't know what it is on the T671. If that resistor goes high resistance the Local Oscillator won't run. Pin 5 is the Hexode screen grid, to HT via a resistor and typically a 50nF or 100nF decoupler to 0V The Mica caps are generally fine. They are rectangular and up to 2000pF It's rarer that paper caps are less than 2000pF, though 1000pF and 470pF are sometimes used.