304TL

The 304TL is a 300 watt general purpose triodes made by paralleling four 75TL tubes in one envelope. The TLs or VT-129 tubes were used extensively in WWII as pulse modulators in the SCR-268 radar sets and as amplifiers in other equipment. Some tubes are only marked VT-129. The TL has a mu of 12 and is usable up to 40 MHz at full rating. The original tube of this type was the 304T . Some of the early 304TL tubes had no caps over the plates, as in the second example, and I speculate (guess) that problems occured with the caps during very high voltage pulse operation. Each of these tubes has a line around the envelope near the shield. I believe they had their upper envelopes replaced with new glass equipped with the capless plates until Eimac learned to "debarnacle" the insides of the plates. Each individual grid came through the glass where they were connected to a ring with a grid cap. Caps over the plates were on all late WWII tubes and all the grid connections were then made internally (3rd example). The grids were paralleled with short leads in these later tubes in a symetrical manner which probably helped at higher frequencies. The fifth example was made by Sylvania and the sixth was made by North American Philips and both have some characteristics of both the early Eimac with its inverted shield and the 304L made by H&K. The seventh example was made by Raytheon.

Length = 7.63" Diameter = 3.56"
Max voltage = 3000
Max current = 900 ma
Fil voltage = 5 or 10
Fil current = 25 or 12.5 amps         GOTO INDEX