[ARC5] Modifying 1625s

[mac]

"Confining" is a more descriptive term for the electrical function the  
plates perform, read the article.  The King's or anybody else's  
English has nothing to do with it.

Dennis D. w7qho
Glendale, CA

*****************

On Jan 11, 2012, at 4:45 AM, Fuqua, Bill L wrote:

> We Americans must appologize for our poor English. These devices are  
> Vacuum Valves and come in boxes of various colours.
>
> ________________________________________
> From: arc5-bounces at mailman.qth.net [arc5-bounces at mailman.qth.net] On  
> Behalf Of Dennis DuVall [scr522 at earthlink.net]
> Sent: Wednesday, January 11, 2012 2:23 AM
> To: ARC-5 List
> Subject: Re: [ARC5] Modifying 1625s
>
> All,
>
> More accurately beam "confining" plates.  This subject comes up about
> once a year.  For more than you ever wanted to know about beam
> tetrodes see <http://www.r-type.org/static/btet.htm>
>
> Dennis D.  W7QHO
> Glendale, CA
>
> ******************
> On Jan 10, 2012, at 10:41 PM, Dennis Monticelli wrote:
>
>> I can only add to the discussion that RCA tubes cannot be modified.
>> Their beam forming plates are tied internal to the envelope.
>>
>> Dennis AE6C
>>
>> On 1/10/12, Glen Zook <gzook at yahoo.com> wrote:
>>> The secret to modifying 1625 tubes to be used in grounded-grid is
>>> to get the
>>> "right" brands.  Some brands have the beam forming plates connected
>>> inside
>>> the glass envelope and some brands have the beam forming plates
>>> connected
>>> outside of the glass envelope.  The latter can be modified and the
>>> former
>>> cannot be modified.
>>>
>>> Glen, K9STH
>>>
>>>
>>> Website:  http://k9sth.com
>>>
>>>
>>> ________________________________
>>> From: Kenneth G. Gordon <kgordon2006 at frontier.com>
>>> To: ARC5 at mailman.qth.net
>>> Sent: Tuesday, January 10, 2012 11:49 AM
>>> Subject: Re: [ARC5] Modifying 1625s
>>>
>>> On 10 Jan 2012 at 1:31, hwhall at compuserve.com wrote:
>>>
>>>>> Just curious. How do you modify a 1625 ??
>>>>
>>>> Certain brands had the beam forming grids brought out of the  
>>>> glass &
>>>> connected to the cathode inside the phenolic octal base. You could
>>>> remove the base or cut a hole in it and rewire the beam forming  
>>>> grid
>>>> to a separate pin, for three independent grids. I think the  
>>>> standard
>>>> practice then was to ground all the grids & run the tubes as
>>>> grounded
>>>> grid amplifiers that typically needed no neutralization.
>>>
>>> Yes. Exactly. In fact, that entire procedure and the amp that
>>> resulted was the subject of an article in at least one ARRL Handbook
>>> of the period. Used 4 ea "modified" 1625s in GG and the ARC-5 roller
>>> inductor in the front. It was a nice-looking little amp and,
>>> apparently, worked quite well.
>>>
>>> As I remember it, it was good for about 300 watts input.
>>>
>>> Since, at the time, many of the hams who were experimenting with SSB
>>> were using such exciters as the CE-10 and CE-20 with 10 and 20 watts
>>> output respectively, this provided a significant improvement in  
>>> power
>>> at relatively low cost.
>>>
>>> I have a CE-20A and the factory "458" VFO which was built on an  
>>> ARC-5
>>> transmitter, the BC-458.
>>>
>>> The combo is a nice little phasing rig with a lot of good features.
>>>
>>> Ken W7EKB
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>> ______________________________________________________________
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