[Boatanchors] Globe King 500A tuning

[Rob Atkinson]

I don't own a GK500 but it sounds like something that used to switch
in on the output tank has gone south.  If the schematic shows any
fixed load padding caps getting switched in on 80 m. I'd check them.
I'd also check the 80 m. tap on the output tank coil and see if it
still has a solid connection.  Ditto for the bandswitch and its lugs.

If you have a swr analyzer one thing I would try is power down the
rig, disconnect it from AC service and let the caps bleed down then
put the rig in its 80 m. position and put the analyzer on the output
feedline jack and put it on 75 m. and while looking at it, get into
the tank and mess around.  wiggle wires, padding caps, work the
bandswitch..generally bang around with a plastic screwdriver handle
looking for the analyzer meter to jump around.  if you see the needle
pop up and down whatever you wiggled is the problem.  the little 20
milliwatts from the analyzer won't do anything to the 500.  try
sweeping the analyzer to get a low vswr reading so when you bang on
something the change is noticeable.  If nothing happens I'd look at
any fixed value caps that get switched in on 80 m (assuming there are
some).

Rob
K5UJ

On Mon, Sep 24, 2012 at 7:40 AM, Charles Ring <w3nu at roadrunner.com> wrote:
> After a month of doing fine on 80. 40, and 20 CW, my Globe King won't
> tune properly on 80. On 80, plenty of plate current off-dip, but no
> proper dip at all, with minimum plate current and max output (less than
> 100 watts) at minimum plate tuning capacitance. Works great on 40 with
> 350 watts out and normal tuning. Somewhat degraded on 20 but functional.
> This is same on antenna and dummy load.
>
> My prior attempt to use it on 15 failed similarly with very low output
> and red 4-400A plate, but now 80 while 40 does fine? Does this make any
> sense? I have used Deoxit on all switch contacts.
>
> --
> *Charles Ring W3NU*
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