[Phil Allison[_3_]]

"Phil Allison"

But I do have an all valve Wien Bridge oscillator using a dual gang
condenser, taken from a 1940s radio.

Owned it since I was 15 years old.

Tube line up: 2 x Mullard 6AM6, 1 x AWV 6BQ5 & 1 x Miniwatt 6V4
rectifier.

Three ranges: 19 to 218 Hz, 185 to 2158Hz & 1889 to 21,899Hz.

Two 18 megohm resistors used in the low frequency range.

The 6AM6s are wired as triodes.

Stabilisation is by an R53 NTC vacuum bead thermistor.

The condenser is electrically isolated from the chassis and lives in a
steel box of its own for shielding.

The shaft is driven by a backlash free, 60:1 worm reduction drive and a
200 point scale.

Verrry silky.

** Ambiguity fix.

The 200 point scale is engraved on a 4.4 inch dia steel disk that rotates
with the worm drive, making 6000 setting points per range.

30 turns x 200 = 6000.


.... Phil