Here's the wiring of the tremolo intensity control in our Valco 62-9033 guitar amp.  The control includes a potentiometer and a switch.

The pot has a resistance of 1MΩ and an audio taper.

When you rotate the pot fully counter-clockwise to the lowest intensity, you can click the effect off completely.

The on-off switch is attached to the back of the pot (right).  It's a single-pole, single-throw (SPST) switch having just two contacts.

Here we snipped off all the connecting wires where they attach to the pot and the switch.

Unsoldering the wires would leave their ends messy—better to strip insulation from cleanly cut ends.

This is our replacement control.  It too has a 1MΩ, audio-taper pot but the switch is different.

The switch mechanism is push-pull, not rotary, and its circuit is double-pole double-throw (DPDT).

We jumpered across the two switch poles and across the two pull contacts (right).  This halves the current through each, increasing their lifetime.

The Push contacts remain unused since we only need a single-throw switch.

The pot's threaded bushing is 7mm in diameter, 2.5mm smaller than the original 3/8" bushing.  For a snug fit, we used two lock washers and two flat washers.

Here's the new Intensity control, installed and wired.

The jumpers made it easier to solder the amplifier's wires to the switch.

Here's the new Intensity control from the outside.

In a way, the push-pull mechanism is better than rotary.

When you push off the tremolo and then pull it back on, the tremolo level remains where it was previously set.

Since the original control knob was missing, we found an acceptable set-screw knob that fit our new control's round shaft.