A Cheaper, Better Surge Suppressor             When using SSRs (solid state relays) in Tube Xmtrs the switched inputs and outputs must be protected the way illustrated below. Also reverse diode protect the SSR input control.  My old trusty DX-100 is completely solid state keyed from the D-104 Mike.

To protect our power, filament and plate transformers I locate a slow MOV and fast transient absorber (both in parallel) near and across (in parallel) transformer primaries.
For 120 VAC protection I Use the following peak voltage devices;
A  Panasonic ( Matshuta ) 220 Volt Bi Directional ( AC ) Transient Voltage Suppressor rated at 1500 Watts   
  Digi-key PN # 1.5KE220CALFCT-ND
And A Panasonic ( Matshuta ) 220 Volt Surge Absorber ( MOV i.e. Metal Oxide Varistor ) rated at 6,500 Watts
  Digi-key PN #  P7230-ND
For 240 VAC Protection  I use;  devices with the same wattage and rated at Twice these voltages I. E. 440-450 Volts. Making sure there is a fuse in series with the hot AC input nearby. If I cannot drill a hole for a 3AG holder I glue a snap in holder on the Chassis.

   In the 1930's through 60's In most all cases our gear expected to be supplied with 110 VAC or 220 VAC not our more common current Mains of 120 or 240 VAC.  In my DX-100 with 120 VAC supplied my filament supplied voltage was nearly 7 volts. Well this started a new idea addition to the MOV, Transorb and fuse above.
    Starting backwards, when I snap my Receivers or Transmitters on everyone notices that the dial lights do Not flash on but gently brighten and my B+ comes up slowly, with less strain on the rectifiers. No, Not step start but a big series resistor in the primary. In my trusty ole DX-100 I mounted a apx 20 ohm 20 watt ceramic power resistor on top of the chassis with teflon wire in series with the hot AC line cord and fuse. Also, take the classic case of the little or big bang coming up the power cord. Yes it is clamped across the primary and easily absorbed by the lossy slow big resistor. Never adding to the dielectric break down of our old magnet wire transformers. No doubt to me how long my dial lights, filaments and old AC transformers are going to last.
     In a plate supply the primary being clamped helps the discharging choke, which could also have a diode across it for some standby problems..

For a extension cord outlet I Also mount two of these devices in parallel in a large power cord plug (plug only), then plug the plug into a 6 to 8 socket outlet extension fused strip. This provides ( one less than original ) 5 to 7 protected outlets for many small items. I use these outlets for the computer area and home entertainment areas, etc.

For 120 VAC protection I Use the following peak voltage devices;

A  Panasonic ( Matshuta ) 220 Volt Bi Directional ( AC ) Transient Voltage Suppressor rated at 1500 Watts    

  Digi-key PN # 1.5KE220CALFCT-ND

And A Panasonic ( Matshuta ) 220 Volt Surge Absorber ( MOV i.e. Metal Oxide Varistor ) rated at 6,500 Watts

  Digi-key PN #  P7230-ND

For 240 VAC Protection  I use;  devices with the same wattage and rated at Twice these voltages I. E. 440-450 Volts.

I Buy These devices from               Call  1-800-344-4539  for a free catalog        

07/30/2009          Back to Ham Index Page       Back to Home page