Parts for the GS-35B
Triode HF Linear Amp Project
(click here for a short RF parts list or here for a short power supply parts list)

RF Deck
Part (numbers match the ND2X shematic but can easily be applied to the others)
Cost
Location
Tube
about
$110.00

 

Tube Socket
$125.00
We will build this much improved mounting fixture
Triode control board
G3SEK and WD7S
$135.00 to $159.00
(http://www.ifwtech.co.uk/g3sek/boards/triode/triode-3.htm)
http://home.earthlink.net/%7Ewd7s/triode_control.htm
Plate choke - RFC2
1.8-30 MHz Amateur Bands including WARC. Ideal for amplifiers using 811A, 572B, 813, 833, 3-500Z, 8877, 3CX800A7, etc. Used extensively in the Ameritron and similar Linear Amps. 1.5A, 225 uH, 4 KV max Size: 5 5/8 L x 1 diameter Ceramic coil form Part Number: RFC-3
$24.95
http://www.rfparts.com/choke.html#plate
Cathode choke - RFC1
Bifilar wound, broadband filament chokes. Suitable for 3-500Z, 3-500ZG, 3-1000A, 3CX800A7, 8877, 833, etc. 30A, 1.8 30 MHz 6 L x 0.7 OD Part Number: FILRFC-30.
Note we do NOT need this high current choke. Only 3 amps needed, not 30.
$17.95

http://www.rfparts.com/choke.html#grounded

Wind this choke from two 48" lengths of #18 wire. These wires should be bifilar wound to fit a 3.5" length of 3/8" ferrite rod. Wind the wire on a metal rod slightly smaller than the 3/8" ferrite rod that the turns will live on.

The single turn cathode choke should be wound the same way with a single 48" length of #18 wire to fit a 1.5" length of 3/8" ferrite rod.

Both chokes will be about 25 to 30 uH.

Cathode coupling caps - C7 & C10 and filament bypass caps C8 & C9 - .01 uf each @ 300 volts or greater.
$5
-
Plate coupling caps - C2
totaling roughly 2200 pf 10 Kv
$25
-
Plate bypass caps - C5
totaling roughly 2200 pf 5 Kv
$15
-
Roller inductor - L2 & L3
about 30 uh to cover 160 meters
$85
-
Strap inductor - L1
A few turns for 10 meters
-
-
Turns counter dial
$25-$35
No longer available from Max - Gain Systems (Allen Bond)
Flexible shaft couplings (2)
$8
- to allow for minor misalignment between the roller inductor and the vacuum variable with their turns counter dials.
Plate tuning cap - C1
About 15-500 pf. Low end is limiting factor. Voltage should be about 2 to 2.5 times plate voltage (7500 v for 3250 v plate. 10 KV to be safe). Vacuum variable may be the best choice here (Jennings UCS-300-15S Vacuum Capacitor, 15-300 pf, 15KV) Click here for more info.
$100
These are either hamfest, internet (maybe Ebay), or buddy parts or see Allen Bond at MaxGain Systems
Loading cap - C3
About 1500 pf broadcast variable, 4 or 5 sections of 350 pf each works. Broadcast variables work and at 2000 watts output into 50 ohms you only see 316 volts.
$10-$25
Old broadcast variable capacitors are best for this. 4 or 5 sections of 350 pf work nicely. You can also use a high value vacuum variable for a lot more money.
Additonal Loading - C4
1000 pf switched in as needed for 160 meters.
$10
-
Plate safety choke - RFC3
2.5 mH to protect you in case plate coupling caps leak or short.
$8
-
Knob for loading
$5
-
Vacuum t/r relays - K1 & K2
Jennings RJ1A or
Kilovac HC-1. Also needed to switch additional capacitance across plate tuning for 160 meters and the B2B is a good choice for that.
$25-$35
Several sources. Max Gain Systems is one.
Compare some of these relays
Plate voltage meter - 5,000 volts - rescaled 50 or 500 ua meter
$15
Meters may have to be rescaled. Also some may want to use the WD7S bar graph display instead of meters:
http://wd7s.home.att.net/ds-1.htm
Plate volt meter multiplier resistors and HV sense for triode board
$15
-
Plate current meter - 1.5 amps
rescaled 50 ua
$15
-
Grid current / plate voltage meter - 500 ma / 5,000 volts
rescaled 50 ua
$15
If you only want 2 meters instead of 3, it is common to use the same meter to measure grid current as you use for plate voltage
Meter switch and knob
-
-
Blower - >100 CFM,
<1500 RPM
$25-75
- Grainger has Dayton 2C647 which is 134 CFM and 1500 RPM for under $50
Filament transformer - 12.6 VAC @ 3 amps for one tube, 6 amps for two tubes.
$20
-Consider using a regulated DC supply. NO center tap needed.
HV Connectors
-
See Gordon's comments and link about Millen connectors
Control connectors
-
Some like Molex connectors and others D style connectors.
RF Connectors
-
Your choice. Some recommend different types input and output so they will not get swapped around. Example: BNC for input, UHF or N for output.
Variac for filament adjustment
$15
Use a 0.5 amp to a 2.5 amp variable transformer here. Some say use a rheostat in series with the primary but that assumes that your filament voltage will be high to start with. Not needed if you use a small switching supply.
Feed thru caps for T/R relay box, triode control board box and meters
$10
-
LEDs for status indicators from triode control board
$10
-
Various barrier strips to make connections for such things as the filament transformer etc.
$10
-
Kanthal-Globar Resistors
Order desk - 716 286 7610
 
Power Supply
Part
Cost
Location
Plate transformer
Need ABOUT 2400-3300 VAC at 1 Amp or more. Bigger if you like more smoke.
$350

Now this could be a LOT less if you're "lucky" and find something good at a hamfest!

HV Diodes
-
Filter Caps
$80
- RF Parts http://www.rfparts.com/caps4.html#oil
Control relays
-
  • 2 each - 24 VDC coil, 30 amp contacts, DPST, for the HV primary control. Also for the step start.
  • 1 each - 120 VAC or 240 VAC coil, 5 amp contacts, DPST, to control the blower.
  • 2 or more - B2B (W2W) vacuum relay for HV switching only if feeding multiple RF decks.
Transformer for control board and relays
$5
28 VAC, 2 amp.
Bleeder
$10
500K @ 100 watts or there abouts. This can be and will likely be made up of multiple resistors in series. 500K is not a magic number. It will provide 10 ma of bleeder current at 5 KV and less at lower voltages. It can be used as part of the multiplier chain for a meter on the power supply to monitor the HV. This can be 50 each 10K, 2 watt resistors on a prototype board along with metering adjustment.
Box
-
-
HV connectors
-
-
Control connectors
-
-
Variac if needed
-
Not needed if the plate transformer isn't over voltage
HV meter, 5KV
-
Optional but will let you see whether there is high voltage in the supply even if you don't see the meter on the RF deck.
2.2k, 25w ww
$1
HV Step Start
47ohm, 50w ww (2-30 ohm, 25w)
$1
HV Step Start
1N4007
$1
HV Step Start
1000 uf, 35 v
$2
HV Step Start
10k, 10w ww
$1
Blower delay
Thermal switch
$1
Blower delay
 
Tom, WB8WJU, ran numbers for the GS-35B at 3600 volts and 1.2 amps as the source input resistance of 1786 ohms and suggested the following values:
Freq.
C1 - Plate tuning - pf
Inductor - uh
C2 - Loading - pf
1.8
477
16.9
2585
3.9
196
7.8
1193
7.2
85
4.2
646
14.3
21
2.1
325
18.1
20
1.3
345
21.3
20
0.99
358
28.5
20
0.56
370

 

Last updated November 27, 2006