Hard to Get Parts
This is a list of parts that may be difficult to find and the source and part number we used. There are a number of other sources available. The least expensive sources are surplus. Other sources include ham radio swap meets or Goodwill type outlets that sell old, discarded radios. Old tube electronics often contain air-variable capacitors, which are the most expensive and difficult to locate parts. Although you can scrounge surplus parts, do not compromise on the quality of the parts. Make sure they are in good condition. Make sure they can stand the high voltages. The biggest problems we have had is with parts that are underrated for the high voltage. Clean old parts, remove dirt and oils that can create conducting paths. Air-variable capacitors are easily damaged, and if the fins are bent, they are very difficult to repair.
Use good RF building techniques. Keep leads short, make good solder connections, and be generous with bypass caps (helps prevent parasitic oscillations). The schematic shows the critical bypass caps, but there are a number of others scattered about as required for our layout.
A fairly good list of sources for surplus parts can be found at http://www.robotics.com/surplus.html
Two sources we used for RF parts were:
Surplus Sales of Nebraska
1502 Jones Street
Omaha, NE 68102
USA
Phone 1-800-224-4567
Email: grinnell@probe.net
RF Parts Company
435 South Pacific Street
San Marcos, Ca 92069
USA
Phone 1-888-744-1943
E-mail: rfp@rfparts.com
The following is the part number and the company we ordered the part from.
SSN = Surplus Sales of Nebraska (address above)
RFP = RF Parts Company (address above)
CAPACITORS
High voltage bypass caps can be found from both dealers. We used the following:
SSN part number: CFD010000R0AAKA .01 uF 1 kV
C4, 8 = 2 to 26 pF, 250 V chassis mount air variable.
SSN part number: CAV-193-8-52, approx. cost US dollars $5
This is a small air variable used to calibrate the RF test point.
The adjusting shaft is grounded. It is mounted so it can be adjusted when the RF generator
is in use.
C13 = 36 to 200 pF, 1500 V, air variable.
SSN part number: CAV-193-8052 air variable, approx. cost US dollars $5
This is the balance adjusting capacitor. It must be completely isolated from ground.
C14 = 9 to 240 pF, 4 kV air variable.
SSN part number: CAV-12-23 9-110 pF air variable, 4 kV rating, approx. cost US dollars
$45
This is the main frequency tuning capacitor. It must be completely from ground.
TUBES
6146B tubes were purchased from RFP.
RFP part number: 6146B, Approx. cost US dollars $30 per pair.
We got a matched set to help with RF balance.
Another possible sources for tubes are:
Radio Electric Supply
1298 S.E. 5th Ave.
Melrose, Fl. 32666
USA
phone: 1-352-475-1950
E-mail: tubes@mindspring.com
web page: http://www.mindspring.com/~gies/res.html
INDUCTORS
L1,2 = 2.5 mH, 160 mA RF choke.
RF choke. RFP part number: 2.5 mH 160 mA approx. cost US dollars $2
DC to DC converter.
A number of people make similar devices and, keep in mind that a pair of batteries
will also work!
You must specify the DC input voltage, the DC output voltage, you must use a unit
that is bipolar, and it must have the isolation you will require.
The isolation must be greater than the float voltage PLUS the plate voltage.
This is the one we used:
Datel part number: BWR-12/105-05, +5V in, +/- 12V out, approx. cost US dollars $44
Datel Inc.
11 Cabot Boulevard
Mansfield, MA 02048
USA, phone 1-800-233-2765
Links to:
RF section schematics and description