6146blue glow

[Lurch]

this question came up on the boatanchors server recently--a blue glow down
between the elements under load indicates gas; a blue glow on the inside of
the envelope itsxelf is indicative of "hard" vacuum (a good thing)...was
the consensus.

At 03:53 AM 1/20/98 -0800, you wrote:
>Murray (multi-volti at SOFTHOUSE.COM) wrote:
>
>==== CUT ====
>Hello:
>
>I think at the <1 kv voltages on 6146x's, it's a gas problem, or
>whatever other low (relative) voltage problems prevail in tubes.
>
>In moderately hv tubes (say 3-5 kV), like 4-400, 3-500, etc, I've been
>told by a now deceased tube engineer that the tube glass often
>fluoresces blue at higher voltages...so I guess it depends where you see
>it. I have seen 4-400's and a 3-400 runnig about 4000 VDC have blue
>glowing glass, but it was nowhere near the grid. filament etc. It was up
>near the anode rod and cooler.
>
>==== CUT ====
>
>I want to build an amplifier with the russian version of the 3CX1500A7
>(GU43b).
>But before that I want to get some experience in building such an pa.
>So I decided to built a 'little amplifier' with abt. 100 W out.
>This little thing should have all the features of his big brother, like:
>
>soft-start for Heater and Plate-voltage
>warm-up and cool-down-Timer
>regulated dc for heater
>protection ciruits for overload, any voltage failures, refl. SWR and so
>on...
>(a similar PA can be seen at: "A Luxury Linear" by Mark Mandelkern, KN5S,
>QEX 05-1996, p.3, ff)
>
>For my little Amp. I want to use either 6146 or PL-500 (HV-Tubes out of an
>Color-TV-Set).
>I have looked at all my HEATH-Equipment (HW-100 and HP23B, SB400) were the
>6146 does a good job.
>But there are +800 V at the plate and +750V when key down.
>
>
>Sure, I could use the HP-23 for powering my PA, but if there is any failure
> I will need a new
>transformer (from P. Dahl ?).
>
>So I have only one transformer (2 x 500V) which would be for my amp (my Old
> Sparky, hihi).
>But 500V is too low for me.
>
>
>Datasheet for the 6146 says that 750 V is the upper limit for this tube.
>But now I only have
>the possibility to give abt. 1000V to the plate.
>
>According to the Email of Murray I think many people transmit with
>increased plate-voltage.
>Is it save enough for the tube ? Perhaps the tube is very sensitive against
> wrong tuning
>and a bad SWR.
>
>It is not the right place for an homebrewed PA, but it is right for a
>discussion on the 6146.
>
>Any comments ?
>Thank you de Gerald, OE1GOD, Vienna, Austria - Europe
>
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>

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