You can put negative bias V on control grid, with filament is hot. Avoid
positive screen grid bias, however, unless there is some plate voltage first.
The electron beam will otherwise all land on the screen grid and over dissipate
it. BTW, the slow application of voltages, a grid at a time, won't help an old
tube much. Just run filament for hour, then some e beam in tube from all
voltages applied, then RF. The ceramic tetrode will be ready for use in hours
or less.
73
John
K5PRO
On Sep 20, 2022, 10:00 AM, at 10:00 AM, amps-request@contesting.com wrote:
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>Today's Topics:
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> 1. Re: Harris RF-110A AM-3924 (Paul Decker)
> 2. Re: Harris RF-110A AM-3924 (Peter Voelpel)
>
>
>----------------------------------------------------------------------
>
>Message: 1
>Date: Tue, 20 Sep 2022 10:22:10 -0400 (EDT)
>From: Paul Decker <kg7hf@comcast.net>
>To: Victor Rosenthal 4X6GP <k2vco.vic@gmail.com>, Amps reflector
> <amps@contesting.com>
>Subject: Re: [Amps] Harris RF-110A AM-3924
>Message-ID: <357125882.546930.1663683730300@connect.xfinity.com>
>Content-Type: text/plain; charset=UTF-8
>
>Thanks Victor,
>For some reason, I was thinking I read the opposite. Would it then
>just be better to apply both screen and full or reduced plate voltage?
>
>
>Paul.
>
>
>> On 09/19/2022 11:33 AM Victor Rosenthal 4X6GP <k2vco.vic@gmail.com>
>wrote:
>>
>>
>> On 19/09/2022 18:17, Paul Decker wrote:
>>
>> <snip>
>>
>> > Step 2. With filiment, apply 500v grid to the 4cx1500's but no
>plate,
>> > and 500 v plate to the 8122's let that soak for a while,
>>
>> <snip>
>>
>> NEVER DO THIS! If you apply screen voltage without plate voltage,
>screen
>> current will go through the roof and destroy the screen!
>>
>> Always ensure plate voltage is present before applying screen
>voltage!
>>
>> 73,
>> Victor, 4X6GP
>> Rehovot, Israel
>> Formerly K2VCO
>> CWops no. 5
>> http://www.qsl.net/k2vco/
>
>
>------------------------------
>
>Message: 2
>Date: Tue, 20 Sep 2022 17:26:00 +0200
>From: "Peter Voelpel" <dj7ww@t-online.de>
>To: "'Paul Decker'" <kg7hf@comcast.net>, <amps@contesting.com>
>Subject: Re: [Amps] Harris RF-110A AM-3924
>Message-ID: <156065D9ECBD4FB981CFF4D38DA6E78A@DJ7WWPC1>
>Content-Type: text/plain; charset="us-ascii"
>
>The 500V are not the 1500B screen voltage, they are the plate voltage
>for
>the 8122 and feed the screen regulator which supplies about 300V for
>the
>1500B screens and 225V for the 8122 screens.
>But never have screen voltage on them without anode voltage, half plate
>voltage is OK.
>
>73
>Peter, DJ7WW
>
>
>-----Original Message-----
>From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Paul
>Decker
>Sent: Montag, 19. September 2022 17:17
>To: amps@contesting.com
>Subject: [Amps] Harris RF-110A AM-3924
>
>Hello group.
>
>I'm getting ready to bring a 40+ year old RF-110A online. I kept the
>low
>voltage portion intact for the filiment, bias, and the 400 Hz chopper
>to the
>lower. I've gutted the old 3phase power supply and replaced the 575v
>screen and 2500v plate transformer with a single phase version.
>
>My plan is to check blower function, then
>
>Step 1. apply filiment without any 2500v plate or 500v gird.
>
>This should keep both the 4cx1500b's and the 8122 plate and grid
>voltage off
>and just run filiment for 24 hours or so.
>
>Step 2. With filiment, apply 500v grid to the 4cx1500's but no plate,
>and
>500 v plate to the 8122's let that soak for a while,
>
>Step 3. Apply half plate voltage about 1200v to the 4cx1500's let that
>soak.
>
>Step 4. Apply full plate and let soak.
>
>Step 5. Run through the amplifier setup and alignment steps in the
>URT-23
>manual.
>
>I've never done a tetrode bring up, so I wonder if it is okay to have
>grid
>without plate or vice versa, no input signal would be applied during
>the
>burn in process.
>
>Thoughts?
>
>Thanks,
>Paul
>Kg7hf
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>------------------------------
>
>End of Amps Digest, Vol 237, Issue 16
>*************************************
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