The humming might be from the vibrator, not the speaker?

I've restored a number of 6 volt vibrator radios including a later model STC. I assume you are sure the 6G6 is correct? Mostly these radios connected the 2 volt filament valves in series-parallel. Yours has a mixture of 6 volt and 2 volt valves?.

I have always imagined the different ways these radios might had been originally powered. Cable from the FJ's battery? Generator on a windmill to charge the battery?

There is a capacitor about .01μF across the vibrator transformer secondary. This is a SUPER CRITICAL part. As well as being high voltage it also needs to be able to handle very high currents. A conventional modern cap will fail quite quickly (melt) in this location. I have some ex Pye colour TV factory parts that are suitable if you need them.

I'd be looking for a broken wire... Dial lamps are decidedly low-tech. There has to be a connection from the 6G6G heater to your 6 volt supply, and the same for the lamps. Somewhere a wire has come off.

Most vibrator sets I have come across have a switch to turn the dial lights on, presumably to save power.

ben

Hey guys,

Have been working away at the radio I've replaced leaky caps a faulty 6G6G valve and serviced the vibrator however the set still only has a quiet hum through the speaker and no other activity there are no poor connections any other ideas?

Have you replaced all of the paper Caps ?. Tested resistors and checked the voltages at the valves.Are the polarised elctrolytics reversed . they must be negative to ground.

That is a point well made. I do not see voltages mentioned. The only difference between the majority of 6V vibrator sets and a mains set is the power supply otherwise servicing is pretty much the same in the radio part as a mains set.

What you have to appreciate with a Vibrator PSU is that they are dirty & have a lot of voltage spikes. I often replace vibrator supply caps with "X" & X/Y mains capacitors. You will often see a PSU cap in that section rated around 1600V and they need to be. That is also a resonant circuit so some cap values are critical.