[AMPS] SB-200

km1h @ juno.com km1h@juno.com
Mon, 13 Oct 1997 17:25:16 EDT

On Mon, 13 Oct 1997 14:49:29 -0400 "George M. Roberts" <kn4ab@home.com>
>On a SB200 being driven by a Kenwood TS520S I get the following
>readings on 40 meters.  The amp is being run off a 120 volt
>line.  Plate mils 60  at rest. 

It should be 90ma

 No-load high voltage is
>2300 volts.  Under load it drops to 1900

Thats about right for a 120V line.

  Max grid 320 mils and plate
>is 350 mils under load.

Are both tubes lit? Also check that both 33 Ohm resistors and both 200pf
caps at the grids are good. A bad tube will blow the resistor and those
caps sometimes cook also. 

With good tubes the grid current will peak right at midscale and the
plate current will be 600-700ma. With 100W of drive power out on 40M will
be around 700W or a bit more on a 240VAC line. 

  Cannot drive it further without exceeding
>capacity of the exciter, which should be putting out 100 watts at this
>time.  I do not have a wattmeter. 

Time to get one. 

>Are tubes soft?

Very possible. I have both new and full output used ones available.
Private E-Mail if you are interested. 

>Is line voltage soft? I can switch to a 220 line which is
>available in the shack.

That will cut down on the sag and give you another 50-100W.

If you plan to use on 10/12M check the parasitic suppressor resistor
values. If they are over 20% high replace them. 

GL  Carl   KM1H

>Thanks for assistance.   73
>George   KN4AB
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