Transmitter Type T1154M, a restoration. /cont

If your T1154 sports an enigmatic and  typed label pasted on the front panel stating ‘Filament Resistance Modification Incorporated’ ... like the one below, this is what it is referring to. In some cases, it might be two 1R5 resistors in parallel. In this case it is a single 0.75R resistor. This is essentially a power saving modification. When the Master Switch is set to STBI,  the 6.3V heater supply is applied to ALL the valves in the T1154 and the R1155. Since the VT104s (PT15) PA valves each draw 1.3A, to save power, a 0.75R resistor is wired in series. This is switched OUT when the Master switch is set to TUNE, CW, MCW and R/T

Filament Resistance Modification

The T1154 employs only 4 valves. The Master Oscillator and Side-Tone/Modulator are type VT105 (ML6) and are triodes. The PA consists of two pentodes, type VT104 (PT15) in parallel.