[AMRadio] problems

[Brett Gazdzinski]

Ronnie,
Some questions.

Are the 813,s in parallel or push pull?
If parallel, did you make any provision for tube balance?

How are you doing the screens?
Separate supply with choke/resistor and high
current protect circuit or dropping resistor?

I run a pair in a continuous tune pi net setup
(roller inductor geared to vacuum cap) at 2000 volts and
400 ma.

I used a separate screen supply (variac) with a dropping resistor
and choke, and it works quite well, the dropping resistor
protecting the screens from excessive changes in current,
and inducing some modulation on the screens along with the
choke.
My rig seems to like both the resistor and the choke to get
good positive modulation peaks.

The 813,s seem to be a great tube, been using the same two
for 10 years without any problems, and they will last
a long time as long as they are protected from
overloads on the screen.

I have had them running at 2250 volts, 500 ma as a test,
without any problems, they seem to have plenty of reserve emission,
and from the way I can pin the 2000 watt pep meter, guess they
can deliver 3000 watts pep without trying to hard, even at
lower plate voltages and/or currents.
 
The 813,s seem stable, working without problems or even
neutralization, at least up to 20 meters....

Have you ever tried using a p touch to label panels?
I paint the panels black, label with white on clear p touch,
then cover with clear paint.

It can look very good if the paint comes out well and you 
get the labels on straight.

I have more problems getting a nice paint finish than anything else...


Have fun!
Brett
N2DTS
 
> I'm building a  homebrew rig with 813's modulated with 805's. Its 
> about 3/4 finished now. I still have to construct the speech 
> amplifier,
> and have some wiring issues to address between the various 
> modules. Finished right now are the RF Deck, Modulation Deck, 
> HV supply for the 813's, HV supply for the 805's, and the Metering 
> panel.
> 
> Im going to put the Millen 90801 exciter and the speech amplifier in
> a black bud reciever cabinet on the desk next to the worlds greatest
> 75A4, and all the rest of it is in a 6' transmitter cabinet.
> 
> Right now it is fondly nick named Frankenstein because it has 3 
> different colored panels on it. I will eventually break them all down 
> and have them all painted the same color. 
> 
> But Frankie is close to coming to life.. I just hope there isn't any 
> HV arcing around his neck when we put the juice to him LOL
> 
> 73's y'all
> 
> Ronnie
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