My wife bought me this radio for my birthday and it's in great shape. Someone spent much time restoring it to good as new condition, even the decals around the knobs have been redone. When I got it, it played great with no problems. But, i'm having an issue with the volume control. The volume stays at approx. 1/4 volume no matter what you do to the knob, untill you get to 3/4 of its rotation, then the volume jumps drastically up. From 3/4 to full clockwise there is no change in volume other than the step up that occurs when you get to 3/4 rotation. I looked under the chassis and at schem. this volume control has 4 lugs on it. The extra lug is for a tone compensation circuit i believe. Is there a way to use a standard 3 lug 500k pot to replace this, or is there another way to address this problem? Thanks in advance.

Have you tried squirting some contact cleaner into the volume control?

The 3ed lug is for bass compensation. You can do without it. If by chance the radio sounds to sharp without it, you can add a .01 capacitor to the plate of the 41 output tube to ground. The tone control switch is an open when in the first position. ( voice ) when switched to bass ( music ) there may be now a little to much bass. You can lessen the values of C-35 & C-36 and tune to ear. The volume control can be taken apart. Sometimes the rivet that connects the lug to the carbon disk is loose making poor connection. You can pinch the rivets with pliers. The wiper arm contacts sometimes can be spread apart to ride on a clean area of the disk. Normally after taking the control apart a visual inspection of the disk will tell the story.