Mica C1 = 5000 pF 500V.
Variable C2 = 25 pF 250V.
C3, C4, C5 = 1000 pF 600v. By-pass (Feedthrough)
C6 = 1000pF, 7500V. DOORKNOB
C7, C8 = 100pF, 7500V. DOORKNOB
C9 = (*) 15 pF variable
C10 = 240 pF, 2000V. variable
* C9 = Observe these photos ( 1
and 2 ), the mechanism is very simple. It
is constructed with a disc of 65 mm diameter connected to the end of a threaded rod through
the front panel of the chassis, with a layer of teflón between the fixed plate and the moving
body of the capacitor.
L1, L2 = 10 turns 1mm silverplated wire, diameter coil = 16mm, long = 20mm.
L3 = 50 turns enameled wire of 0,6m/m on form teflón of 20mm diameter.
L4 = Z-50 RFC or 48 turns of 0,6mm wire on form teflón of 68mm diameter.
L5 = 16 turns with 2 windings of 2m/m enameled wire in parallel, on bar ferrite of 10mm
L6 = 5 turns of tube receives of 1/4", diameter coil = 35mm, long. = 45mm
L7 = 7 turns of 2,5mm wire, diameter coil = 20mm, long = 40mm.
L8 = Z-50 RFC or 68 turns of 0,2mm wire on form teflón of 6mm diameter.
For these levels of power I have used two types, and both work perfectly:
- Relays vacio Jennings RJ1A for high speed switching or heavy use (EME-JT44, FSK441)
- coaxial Relays TOHTSU type CX600NL for "normal" work (these tend to arc in above modes).
The bracket that holds the GS35B and the one of connection of the anode are of brass or (better)aluminum of 10mm thickness.
See the photos for their implementation.
The chimney of the valve is a tube of teflón with inner diameter = 100mm.
PLATE CONTROL and POLARIZATION
Instead of using the classic circuits of polarization and measurement I have used
TRIODE BOARD of
The design is excellent, but we will have to carry out some small modifications for its use with this amplifier in heavy regime.
MODIFICATIONS TO CARRY OUT:
- to place resistance of 2k7 in noticeable place HI - B
- to replace R8 of 100 ohms-1/4W by 180 ohms-1W
- to replace R9 of 47 ohms-1/4W by same value-1W
- to place a small refrigerator upon zener adjustable TL431
- to install the Q1 transistor, TIP147 in a sobredetermine the proportions refrigerator.
- when coming out to connect 3 resistance in parallel of 47 ohms-50W of the emitter of the Q1 transistor, TIP147.
With these measures the polarization (BIAS) will be able to work all along correctly and to total power.
WHERE TO LOOK FOR THE MATERIAL?
Here you have the directions where I have found the electronic equipment, almost all this in:
RF PARTS but first look at:
Barend Hendriksen in Europe
The vacuum relays in - Max-Gain systems
Triode Board in RF PARTS or
DOWN EAST MICROWAVES
If you do not find some material or you need information, you can get in contact with me,
EA3AXV 50MHz PA Page (Spanish)
Back to English PA page