The modulation rate control on this wonderful Sovtek Small Stone phaser effect pedal had broken. While the unit is in the shop, could the Unbrokenstring Crew also add a 21st century DC pedal power jack to the unit?
Like a message in a bottle, this pedal has the look and feel of a relic from another planet. Even the switch looks like alien technology.
Removing the top cover reveals a heavy steel plate that holds the major components. Look at the LED holder!
The control for the phase modulation had disintegrated. Not much was left holding the shaft in place.
The back side of the modulation control was not out of the ordinary beyond the Cyrillic alphabet. Perhaps it could be rebuilt using parts from another similarly-sized potentiometer.
We have removed the old potentiometer from the circuit.
The tabs on the back cover of the potentiometer can be peeled back in order to disassemble the unit.
Interestingly, the internals of this control are completely different than what we might expect from a domestic control. This potentiometer is a ‘reverse audio taper’ component. The Russians achieved this by mounting the resistive element on the opposite side of the main wafer of the control, effectively reversing the direction of the taper.
So, it appears that we need to find a control that is close to the physical size of the old part, so we can reuse the knob.
We are working in millimeters here, in case you are wondering.
An aluminum bushing allows this smaller shaft to fit in the Russian knob. Perhaps we have another degree of freedom in our search for a proper replacement.
This bushing can be removed… a good thing that will allow us to do some gun-smithing if we need to do so.
The knob is not quite big enough to allow a quarter-inch shaft to be substituted.
So, we located a reverse audio taper control custom-designed for Neve recording consoles. Yeah, I got connections.
This part has an appropriately-sized shaft that will permit us to use the original knob. Good news!
The new control is wired into the circuit in the same manner as the old one. Teflon spaghetti tubing handles the high-temperature insulation duties here.
These little spacers were rattling around in the enclosure after the circuit board was removed. Where do these go?
Turns out, they are spacers that go on top of the cast bosses in the bottom of the original box.
The new power jack is mounted and wired into place, along with new steel Switchcraft in and out jacks.
The whole arrangement is now fitted back into the case.
An internal nine volt battery is used for powering this unit for checkout.
We have a winner! Time to tighten down the screws and button this unit back up.
Here is the top cover with the new control installed.
The case cover is now back on.
The owner wanted to leave no question regarding whose pedal this was. Mine!!! Mine!!
Thanks for reading all the way to the end!
CONTACT – David Latchaw EE