Good evening all,

Finally worked out that the radio I am working on appears to be a Music Master A6 radio.

I'm trying to make sense of the schematic. Everything lines up exactly, including resistors and capacitors. The only thing I can't work out are the two potentiometers that I have marked in colour. The blue pot lines up exactly as in the radio, however I have no idea about the red pot.

My question is, what does the red pot do exactly? The blue pot is the volume control knob, but the red pot is nowhere to be found on the radio.

Will it matter if the red pot is not included and wired up in the radio?

Image removed - see e-mail

Photo uploaded.

I'd say it's the tone control.

Yes, it is the tone control using some negative feedback to improve the sound quality.

Love the Typo I think that might be 6J8 especially if its got Shortwave

Yep, worked out pretty quick that it was a 6JB!

The weird thing is that there is no tone control knob. The on/off switch is exactly that: either off, on with no dial lamp and on with dial lamp.

Would not having the tone control in the circuit affect the radio at all? Will it still work and be able to recieve?

So, you are saying that your particular set has no tone control circuitry at all (neither of those caps, nor the resistor and the pot) and no place to mount a tone control pot? If so, then it appears that you may have a variant of the A6.

A receiver doesn't need a tone control in order to operate. The tone control merely allows the user to adjust the tone to personal preference.

Yes, this is a vibrator powered version of the A6 as far as I can determine, and there is definitely no tone control pot/resistors/caps on the chassis.

Once it has been recapped and ready to go, I'll see how it sounds.

There may still be a fixed network of parts to perform the negative feedback function. Take a look at the 6V6 anode connection and see if there's a capacitor connected there, then see where it leads to.

There is a capacitor (0.01mF, 600V) attached to the anode, however it connects to the output transformer on the screen grid side. According to the schematic, this is incorrect. The capacitor should branch off the anode back to the tone control. No other components of the tone control exist.

There have been a few connections which don't follow the schematic around the 6SQ7 and 6V6 tubes. I'm changing them back to what the schamtics say.

That still sounds odd 0.01 mfd I would expect across the OP transformer screen to grid. Plate to ground 0.005 mfd.

The DC switch on a battery set would in most cases loose the dial lights, once its put on the station, as they consume battery.

The answer to the tone control lies in it being provided for as a potentiometer, or switched as part of the on off switch?

One would half expect also terminals with the rest of the parts if there was a tone.

If this is a hack anything can happen: Some mods I have seen were absolutely bizarre.

The answer to the tone control lies in it being provided for as a potentiometer, or switched as part of the on off switch?

Alarum says in post #1 that there is no sign of a tone pot. Presumably this set has only two knobs: tuning and volume.

Alarum, please post some photos of your radio.

this is a vibrator powered version of the A6 as far as I can determine

The only Music Master vibrator sets that I can find in the AORSM have the typical line-up of 2 volt valves. How are you powering your set?