Re: red 304TL

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Steveh by way of Terry Fritz <twftesla-at-qwest-dot-net>" <steve.g.hall-at-attbi-dot-com>

Steve,

I checked in my tube data and it didn't specifically state how hot the plate
can get for that tube. It did state that the plate for a 75TL tube runs
"visibly red" at maximum power. What does this have to do with a 304TL, you
ask? A 304TL is actually composed of 4 parallel 75TL tube elements. I would
expect the 304TL plate to also glow red at full power.
Some tubes, such as the 450TH, 4-250A and 4-400A state that the plate can
run red-orange at maximum power. Although the plates in all of these tubes
are constructed of the same material, I wouldn't recommend running the 304TL
as hot for the following reason:
It has four plates clustered together. The outer surfaces of each plate
radiate to the glass bulb and therefore will run cooler. The inner surfaces
of each plate face the three neighboring plates and therefore will not
dissipate heat as efficiently. The inner surfaces will probably get hotter
and it would be more difficult to see a hot spot forming here.
To make a long story short, I would only let the plate get red hot. Also, be
sure to use the propper finned heat sink connectors on the plate and grid,
this will prevent the delicate seals from cracking and greatly increase tube
life span. A cooling fan will also help.
18" of arc from a tube with a 300 watt plate is about as good as you can
hope for. The only ways to squeeze more out of it would be to limit the duty
cycle (stacato) or increase circuit efficiency. If you run a higher plate
voltage with a higher load impedance (less plate current) you can get more
power out. A typical triode power oscillator runs at 75% plate efficiency,
however, it is possible to get 80%. This can make a big difference. At 75%
efficiency a 304TL will put out 900 watts, at 80% efficiency it will put out
1200 watts! Hopefully this will be of help.

Steve


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Wednesday, November 13, 2002 4:56 PM
Subject: red 304TL


 > Original poster: "Steven Ward by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<srward16-at-hotmail-dot-com>
 >
 >
 > Hello,
 >
 > Im working on my 304TL VTTC, and with a doubler im up to about 18" with
 > only one tube.  Problem is, the tubes getting red to say the least!  I
 > would actually have to say almost an orange!  I know this is probably
 > bad.  But, does anyone know how red these tubes are spec'd to run?  I
think
 > im up to 90v on the variac, so thats about 3000v or so on the plate.  Im
 > going to look into staccato circuits, but for now i would like to know how
 > red/orange can this tube run.  If anyone has this type of experience or
 > info on this tube, let me know.  Thanks,
 >
 > Steve Ward.
 >
 >
 >
 >