[ARC5] 6k8 - 12k8?

[Greg Mijal]

No
It'snot mislabled.  There is a 12K8 tube.  If you look at a tube manual you 
will see that the 6K8 was also available in 12v versions.  If I remember 
correctly, the pin out is the same.  Only the heater voltage is different.
73's
Greg
WA7LYO
Kinston NC
----- Original Message ----- 
From: "Leslie Smith" <vk2bcu at operamail.com>
To: "ARC-5 List" <arc5 at mailman.qth.net>
Sent: Friday, April 15, 2011 4:39 PM
Subject: [ARC5] 6k8 - 12k8?


> Dear list,
> I have a valve (or "toob") marked 12k8.  Manufacturer: KEN-RAD,  The
> cold filament resistance is around 3.9 to 4 ohms.  This is out of the
> set, unconnected.  Is this a 6k8 that is mis-labelled?  My experience to
> date has been that the cold resistance of any of the VT13x "toobs" is
> around 12 ohms.
>
> I'm uncertain about the source of this valve.  It came from a box with
> valves, IF transformers, chassis screws etc that was in another box
> containing a "scrap" BC-453 I am in the process of rescuing from a
> morbid fate.  In other words I don't know where it came from.
>
> I found it in the following manner.  Last night I was at the stage of
> re-fitting the valves to the "scrap" chassis; I inserted a pair of
> valves, turned the filament supply "on" and measured the voltage at the
> junction of the two filaments.  In this case, that turned out to be
> about 20 volts.  Hmmmm.  (Thinks ... this is unusual, Mr. Ohm is doing
> strange things ....)  Do various things - make various checks.  Mutter
> about socket resistance and promise to never wash another chassis in
> Dot's Bath Cleaner.  Got another 12k8 (this one was made by RCA) and
> measured the cold filament resistance.  Around 12 ohms.  Put this 12K8
> (by RCA) into the chassis, and measured the voltage at the center point
> of the two filaments.  Near enough to 12 volt.  (Thinks:  Dot's bath
> cleaner may not be so bad after all.)
>
> I imagine this valve somehow got from the 6K8 batch into the 12K8 batch
> before the labelling machine at KEN-RAD.  Any-one seen this before?  Or
> maybe it's just a broken filament in a 12K8?
>
> 73 greetings from Australia
>
> Les
>
> -- 
>  Leslie Smith
>  vk2bcu at operamail.com
>  (end)
>
> -- 
> http://www.fastmail.fm - Send your email first class
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