Hi Pete,
I'll pick up a new tube then I'll play with the bringing the old one back to
life :-)
On another note I borrowed another VOM to make sure the filament voltage
wasnt too high. The brand new fluke showed only 4.6 volts. I then
liberated my old Simpson 260 from the garage and it alse reads 4.5-4.6
volts. Oddly enough if I rewire the amp back to 120vac it shows 4.9-5.0
volts on the filament. Each leg of the 220 line is exactly the same voltage
(117.5) so whats up with that?
Thanks again,
Kevin
----- Original Message -----
From: Peter Chadwick <Peter_Chadwick@mitel.com>
To: Kevin Polchan <kpevin@mediaone.net>; 'measures' <measures@vcnet.com>
Cc: amps <amps@contesting.com>
Sent: Monday, February 21, 2000 5:06 AM
Subject: RE: [AMPS] 3-500z going dead?
>
> Rich says:
>
> >>Seeing the tube is 18 years old and who knows where it came from I think
> it >>could be dying a normal death, hi hi.
>
> >I have an 8163/3-400Z that was mfg in 1967 and it still gives full
> >output. The best way to test emission is to temporarily increase
> >filament potential approx 1/2V. . If the output increases, the end is
> >near.
>
> I have a 6L6G mfd in 1935, and it still has full output. But in Kevin's
> case, it could well be the tube is dying. Rich's idea will show if the
> emission is going. If it is, then you could try 'rejuvenating' the
filament
> - you've nothing to lose. The usual method is 50% overvoltage on the
> filament WITH NO OTHER VOLTAGES applied for 20 or 30 seconds, and then run
> at +20% overvoltage for a minute or two, and +10% for 30 minutes. Some
> people use different times, and there's no guarantee. But especially if
the
> tube hasn't had a red plate (so that there could be some gas in it), then
> flashing the filament to get a fresh layer of thorium up to the surface
> could get a few more years out of it. As I say, you've nothing to
> lose....but it's probably worthwhile getting a new tube first.
>
> By the way, make sure the tube is upright, because if it isn't, the
> increased filament temperature could lead to sag and welding of filament
and
> grid.
>
> 73
>
> Peter G3RZP
>
>
>
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