To use a Triode a Bias or zero signal current is needed. In “ancient” times it was done by a zener diode. But with popular tubes like 3CX1500 / 8877 / GS31b / GS35b we should need 50W zener diodes. These are hard to find, easy to break and expensive. This board is a “transitorized zenerdiode” It contains a TL-431 “adjustable zenerdiode” and a buffer darlington transistor. For higer voltage than the normal max 39V an aditional 15V zener diode is added to get as high as 54 Volt.
Several people already designed Triode bias circuits, this circuit is in use and has been copied by many hams all over the world. It is basically the reference design from the datasheet.
|
Tube(s) |
Grid current |
Bias voltage |
|
GI7b |
100 mA |
12–15 V * |
|
2x GI7b |
150-200mA |
12–15 V * |
|
3-500Z |
200 mA |
9 V |
|
2x 3-500Z |
400 mA |
9 V |
|
3CX800 |
50 mA |
5–8 V * |
|
2x 3CX800 |
100 mA |
5–8 V * |
|
GS31/35b |
400 mA |
24–40 V * |
|
2x GS31/35b |
800 mA |
24–40 V * |
|
3CX1500/8877 |
200 mA |
8–12 V * |
|
2x 8877 |
400 mA |
8–12 V * |
|
TH308,328,338 |
25 mA |
2-22 V * |
You are bidding on a Complete KIT PCB and COMPONENTS INCLUDED !!
you will get a BARE PCB all needed components, and a description how to assemble including schematic and bill of materials.
There is NO heatsink and NO mounting hardware included.