[Milsurplus] [Fwd: Re: [ARC5] 7V and 14V Tubes]

[Al Klase]

OK, my two cents:

In the early going tube filament voltages were not standardized.  With 
the introduction of mass production tubes like '00 and '01 after WWI, 
the industry standardized on 5 volts.  It's a round number, and 
convenient to use with a 6-volt storage battery.  As the battery sagged, 
a filament rheostat allowed for adjustment.  Some power tubes were rated 
at 7.5 and 10 volts on the filament.

When AC operated sets became popular, some other voltages come into 
play, filament voltages below 5 volts were helpful to control hum.  
Hence 2.5 and even 1.25-volt tube like the '26 triode.

As someone mentioned, 6-volt tube were developed to support car radios.  
The voltage is nominally considered to be 6.3, but the tubes are 
perfectly happy at 7 volts when the engine is running, and the battery 
is being charged.  Of course there was a natural progressing to 12.6 volts.

I think loctal tube were designated 7 and 14 to avoid confusion.  Their 
ratings are very similar to the 6xxx and 12xxx tubes.

I'll stop now.

Regards,
Al

On 4/30/2012 9:03 PM, J. Forster wrote:
> ---------------------------- Original Message ----------------------------
> Subject: Re: [ARC5] 7V and 14V Tubes
> From:    "J. Forster"<jfor at quikus.com>
> Date:    Mon, April 30, 2012 5:59 pm
> To:      "Geoff"<geoffrey at jeremy.mv.com>
> Cc:      arc5 at mailman.qth.net
>           "Robert  Eleazer"<releazer at earthlink.net>
> --------------------------------------------------------------------------
>
> That logic explains the need for a separate transformer winding, but not
> the 5 Volts.
>
> Having a few hundred volts between the heater and cathode of a tube can
> lead to failures...  big time. Viz. the AC power supply for the Cabadian
> WS19. A 6X4 failure often destroys the unobtanium power transformer.
>
> -John
>
> ===================
>
>
>>> Only recently I discovered there are some 5V filament tubes around, too,
>>> and I have no idea why....
>>>
>> Primarily because it was prudent to have the rectifier tubes on a seperate
>> filament winding so that a short circuit or arc didnt take out the other
>> tubes..
>> For vehicle use there were 6V rectifiers such as the 84/6Z4, 6X5, 6X4,
>> 12X4.
>>
>>
>>> Wayne
>>> ______________________________________________________________

-- 
Al Klase - N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/