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Re: [Amps] NOS 811's & 30L1

To: Mike Lord <>, "" <>
Subject: Re: [Amps] NOS 811's & 30L1
From: "Fuqua, Bill L" <>
Date: Wed, 21 Sep 2011 21:17:32 -0400
List-post: <">>
If I recall the Johnson Viking 500 ran 2kV on the plates of the 811A modulator 
I don't think there were many reports of problems using the tubes available 
those days.
Bill wa4lav

From: [] On Behalf Of 
Mike Lord []
Sent: Wednesday, September 21, 2011 3:25 PM
Subject: [Amps] NOS 811's & 30L1

I just completed the restoration of a 30L1, i.e., new Harbach board, "matched 
set" of 811's.  Brought the unit up slowly with a Variac.  110 VAC line 
voltage, 1800 VDC unloaded on plates.  All seemed ok.  Hooked up the unit to 
the rig.  Turned the 30L1 on and blew up the glitch resistors.  Smoked up the 
place.  Checked the unit for damage beyond the glitch all checked ok.  Brought 
the unit up slowly with the Variac and at about 400 VDC one tube began showing 
purple glow and slight arcing.  Changed out the tube and all was well.  Here's 
my question.  The 811 vendor tells me the problem is the 1800 VDC on the 
plates.  "Too much for an 811"  I realize the caps on the Harbach are large 
thus more B+, but there have been many of those boards sold.  The 30L1 book 
says 1600 VDC unloaded.  The 811 is rated at 1500 V.  So what are all the 30L1 
owners doing besides changing over to a 572B?

Thanks.  Mike K4ELV
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