Advance model B4B Signal Generator

Serial number

 

Covers 30kHz to 30 MHz in 6 switched ranges with a calibration accuracy of +/- 1% of the scale reading. The modulation can be internal (400 Hz) or external (10 Hz to 10 kHz). The meter is used to monitor the modulation (0-80%) or the RF amplitude.
It has 3 Valves: ECC91 6SN7GT and 6X5GT
 It works well but the meter has never indicated correctly since it was given to me in 2011. Having seen a tip on the web I recently (November 2014) decided to investigate further and replace several of the capacitors associated with the AF oscillator and modulator. This effected the desired meter response but only temporarily. I discovered that the meter was accurate but the pointer would often not rise beyond about quarter scale. After dismantling the meter, refixing the loose glass and re assembling it now functions correctly (touch wood!) 

    

views of the interior with screening covers removed (lots of screws to undo)

   

Advance made versions of this very popular signal generator for many years, I think mine dates from early 1961 based upon the date codes on the capacitors. There is a useful capacitor dating page HERE. Later models have rectangular meters and BNC coaxial connectors The advert for an earlier model dates from 1948

What is it worth?

In recent auctions during 2014 the Advance B4B has sold for between 27 and 48  (the later models fetch a better price)