Series III RangeMaster
Owner’s Manual
November 2016
2
Series III units all use the Welwyn preset potentiometer as the boost control, as
original. The pots are all 25K Ohms, which make them have a little more gain than
the original when turned all the way up.
The (3) resistors are carbon composition. Two of these resistors are used to bias the
transistor; their values will be different from unit to unit, because each transistor is
slightly different and is biased to the middle of its range. A schematic of the
RangeMaster is attached to the inside of the black cover; here you will find the gain
measurements of the OC44 used in the device and the values of the bias resistors for
that particular OC44.
Each OC44 in each RangeMaster is biased at a battery voltage of 8.2 VDC. This is
about mid-way between a new battery and a dead battery and ensures that you will
get optimum performance of your RangeMaster throughout the life of the 9V battery.
A 9V “wall wart” supply is not an option; this is a PNP device. Almost all "stomp
boxes" are NPN. They hate each other.
Germanium transistors are temperature sensitive. I bias the transistors at 70 degrees
F. In the summer, or under hot lights, the temperature rises, and the gain of the
transistor will rise. Just something to be aware of. (This is true of the FuzzFace,
another legendary vintage Germanium effect, and it has been said that Stevie Ray
Vaughn liked his FuzzFace to be hot, so he could take advantage of the extra gain.)
The OC44 is in a socket, so is removable in the event of failure or if you want to
change to a different transistor. For your information, the transistor should be
inserted into the socket with the Collector leg (usually marked with a dot or a notch)
on the left when looking at the face of the device. If you replace or change the
transistor you must check the bias.
