[MT70B]

I am not familiar with vintage Philips Radios and therefore not sure what to expect from the balance control on a B6X34A/54 that I am working on. The control has almost not effect fully turned right or left in either the stereo or mono modes. I have ohm'd out the control and traced the wiring along with checking the capacitors associated with the control and all seems fine.

Looking at the schematic it appears the control only works in the stereo mode where the wiper of the control gets grounded by the stereo/mono switch. I have verified that the switch does apply the ground to the wiper. Either end of the balance control goes to between a resistor divider supplying plate voltage to the tube. The control is then coupled by a capacitor which blocks the plate voltage from the control. The audio from the tube is taken off the plate of the tube through a different coupling capacitor (before the divider network) and on to the next stage. This means that the balance control only affects the signal present in between the resistor voltage divider that feeds the plate of the tube.

Anyone familiar with how these early 60's Philips balance controls worked? Is it normal to have almost no impact on the actual balance, or am I missing something.....? Otherwise radio plays and sounds good in FM, MW, and SW modes.

A piece of the schematic is attached for reference.

Thanks for your feedback!

Mike