GS-35b HF Amplifier
Inside the amp is a Freed 28130 filament transformer part # (TP)CE78990 purchased new from
Surplus Sales of Nebraska. The plate DC blocking capacitors are a pair of Sprague 500pF/30KV
RF type attached to the top of the 7 1/2" x 1" plate choke wound with #22 AWG
enameled wire. The GS-35b sits in a modified Penta-Labs socket and chimney originally used
with a PL-172 tube. I removed the grid bypass capacitors and finger stock and fabricated a
single piece of aluminum (cut out on my scroll saw) for the tube body grid ring. I cut the
hole slightly oversized and attached the previously removed finger stock into this new hole.
The tubes grid ring fits very snug inside the new hole. Small clamps are attached to the
socket and clamp the tube into place. All socket parts (other than the aluminum one) are
silver plated. The roller inductor is a silver plated 3/8" edge rolled bar-stock type with
6 internal rotating brush contacts, not the typical edge mounted contact wheel type. It allows
tank circuit resonance over the entire band and covers 10 - 160 meters continuously. The plate
tuning capacitor is 250pF, 3/8" spacing and the loading cap is 1000pF. The meters are
mounted behind an aluminum box and are fed from the sub-chassis via a metal conduit shielding
them completely from any RF.