Johnson Valiant correct PA bias voltage

[G4OJY]

So I've just finished restoring a Johnson Valiant transmitter but I've seen 2 figures quoted for the PA bias voltage of -52V and -69V. Which is the correct one to use? I'm only interested in transmitting on AM.

Andy G4OJY

[ae7db]

Assuming you have an original Valiant, with bias adjustments being made with the sliders on the resistor, the attached clip from the manual calls for grid voltages of -70V for the rf finals and -55V for the modulators.

Dean

[G4OJY]

Assuming you have an original Valiant, with bias adjustments being made with the sliders on the resistor, the attached clip from the manual calls for grid voltages of -70V for the rf finals and -55V for the modulators.

Dean

Hello Dean, its a MK1 Valiant which has had the mods to change it to the MK2, so there are 2 bias potentiometers on the side.

[ae7db]

Andy,

OK.  The manual for the Valiant II, as shown in the attached clip, calls for setting the rf final grid bias to -69V.  It calls for adjusting the bias pot for the modulator finals to achieve a static current of 60mA rather than specifying a bias voltage.

Dean