Ultra TU3
Band III Convertor

The case is very similar to Ultra's late 40's baeklite radios and indeed may have used a modified version of the original mould.
The channel selector is nice and optimistic, with one setting for the BBC and two settings for the "alternative" riff-raff.

Two version were produced, one for receivers originally designed for Band 1 channels 1, 2, 4 or 5 and the second for receivers originally receiving channel 3. This is because the I.F. frequency for the channel 3 sets differed to that thos for the other channels, the different I.F. presumably required so that harmincs of the I.F. did not interfere with the sound and/or vision signals of channel 3.

Th convertors were designed to operate with Ultra's own receivers, specifically the V71 (illustrated opposit), the V72, W72, Y72, Y73, VA72, YA72, YA73, YE73, V80, W80, V84, W84 and Y84.
Whilst the main circuit is based around a combination of PCC84 and PCF80 valves - just like almost every other band III convertor - the power supply is a little unusual. The convertor is intended for use with A.C.-only sets whose valve filaments would all have been wired in parallel. A connection to the convertor fits into a valve socket in the receiver and the 6.3V filament supply for that valve is stepped up, auto-transformer style, to generate 16V for the convertors series-connected valves. A secondary winding is used to generate the required HT voltage via a full wave bridge rectifier.