Don,
I was in qso with Jay, n2wwl today, and we were talking about
the 32v3, and the voltage it runs at, Jay runs his on the low voltage
position,
about 600 volts on the plates.
I run mine on the 700 volt tap, 180 to 200 ma.

The panel meter says 800 volts high voltage, but I put my
DMM on it and was very surprised to find 940 volts on the plates.

I have been running them that way for 15 years with the same tubes
in them, and used to use them quite a lot.

I get 100 watts out, and 350 watts pep.
I have solid stated the power supplies, which explains the high
voltage.

I think, as long as you don't exceed the plate dissipation,
you are likely ok with most tubes.

Brett
N2DTS

>
>
>
> >Collins runs them at over 700 volts in class C plate
> >modulated service (32V series).
> >If they don't arc over, and you don't exceed the plate dissipation,
> >what would be the problem?
> >
>
> That's a good point.  I recall an article pre-WW2 in QST
> which described
> getting high peak audio power from modulator tubes by running
> unusually high
> voltage on them, but staying within the rated dissipation
> rating.  A point
> was made that for example, the 807 is rated for a maximum of
> 600 volts plate
> modulated.  That means the peak voltage would be at  least
> 1200 volts, and
> that doesn't hurt them, and is still within factory specified
> ratings.  So
> for intermittent service, you should be able to run as much
> as 1200 DC volts
> on an 807.  I think the limit on plate modulated voltage
> would be the point
> where arcovers would begin.
>
> However, I do recall using a quad of p-p parallel 2A3's in my
> audio driver.
> I didn't have a proper driver transformer at the time, so I
> ran them @ 400
> volts/30 m.a. each tube.  They are rated at 300 volts/40 m.a.
> maximum in the
> RCA manual.  That way I could get plenty of peak driving
> voltage to the
> class B grids, despite having a driver transformer with too
> much stepdown,
> but with exactly the same plate dissipation as per RCA
> recommended ratings.
> They worked great, and drove the modulator tubes with very little
> distortion.  But I noticed that within a  few months, the
> 2A3's would get
> weak.  I went through a couple of sets that way.  Finally, I
> obtained a
> proper driver transformer with the proper turns ratio, and
> slowered the
> plate voltage back to 300v, and changed the bias so that each
> tube would
> draw 40 m.a., and now I have had the same set of 2A3's for
> almost 10 years,
> and they still test good.  Maybe just  a coincidence, but at
> the current
> price of a new 2A3, I don't feel like trying to find out.
>
> My conclusion is that some tubes may not take overvoltage
> very well, while
> others will not be harmed, and the only way to find out which
> ones is to try
> them and see.  If your tubes seem to be short lived, go back to the
> recommended parameters.
>
> -K4KYV
>
> _________________________________________________________________
> High-speed usersbe more efficient online with the new MSN
> Premium Internet
> Software. http://join.msn.com/?pgmarket=en-us&page=byoa/prem&ST=1
>
> _______________________________________________
> AMRadio mailing list
> [email protected]
> http://mailman.qth.net/mailman/listinfo/amradio
>

Reply via email to