It used the same B+ on the plates of the 811As as the 4-250A final.
73
Bill wa4lav
________________________________________
From: amps-bounces@contesting.com [amps-bounces@contesting.com] On Behalf Of
Fuqua, Bill L [wlfuqu00@uky.edu]
Sent: Wednesday, September 21, 2011 9:17 PM
To: Mike Lord; amps@contesting.com
Subject: Re: [Amps] NOS 811's & 30L1
If I recall the Johnson Viking 500 ran 2kV on the plates of the 811A modulator
tubes.
I don't think there were many reports of problems using the tubes available
those days.
73
Bill wa4lav
________________________________________
From: amps-bounces@contesting.com [amps-bounces@contesting.com] On Behalf Of
Mike Lord [k4elv@bellsouth.net]
Sent: Wednesday, September 21, 2011 3:25 PM
To: amps@contesting.com
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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