[ARC5] 6k8 - 12k8?

[Leslie Smith]

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)

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