26-10-2022, 08:17 PM
Recently bought a pair of Mazda 6F33 valves with the view to the construction of Band 1 TV sound and vision modulators.
This pentode valve has special grid 3 characteristics making possible for this application. To prevent G3 becoming positive I believe the valve has a diode connected between G3 and the cathode.
The carrier will be injected into the control grid and modulation signal into G3.
From the web: "The 6F33 was a pentode with characteristics particularly suited for use in timebase generators. The Mazda data sheet states "The 6F33 has a short cut-off suppressor grid characteristic which makes it particularly suitable for use in modulator, variable reactance and timing circuits." The suppressor grid could thus be used as a second control grid, e.g. in the transitron timebase oscillator circuit [see References]. Note that for its use as a control grid, the pitch of the suppressor grid wires is closer than that for the EF91".
From the Radiomuseum: https://www.radiomuseum.org/tubes/tube_cv2209.html
The Murphy TPG11 TV sync and pattern generator employed the 6F33 as the modulator.
Geordie McBoyne.
This pentode valve has special grid 3 characteristics making possible for this application. To prevent G3 becoming positive I believe the valve has a diode connected between G3 and the cathode.
The carrier will be injected into the control grid and modulation signal into G3.
From the web: "The 6F33 was a pentode with characteristics particularly suited for use in timebase generators. The Mazda data sheet states "The 6F33 has a short cut-off suppressor grid characteristic which makes it particularly suitable for use in modulator, variable reactance and timing circuits." The suppressor grid could thus be used as a second control grid, e.g. in the transitron timebase oscillator circuit [see References]. Note that for its use as a control grid, the pitch of the suppressor grid wires is closer than that for the EF91".
From the Radiomuseum: https://www.radiomuseum.org/tubes/tube_cv2209.html
The Murphy TPG11 TV sync and pattern generator employed the 6F33 as the modulator.
Geordie McBoyne.
