T12 Coloured Tubes And Starterless Gear?

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Tom
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T12 Coloured Tubes And Starterless Gear?

Postby Tom » Thu Jun 16, 2011 11:05 pm

I recall reading in the old Thorn catalogues that coloured tubes were only suited to ballast and starter switch. Upon switch-on, the starter closes and preheats the tube's cathode filaments. Upon opening, the magnetic field within the ballast collapses, causing a voltage pulse which strikes the tube. This is often repeated twice or more, causing the distinctive blinking at startup.">switchstart gear and were not suitable for starterless circuits such as SRS and Quickstart. I think this mainly applied to Red and Gold tubes and that the remaining phosphor coloured (appearing white unlit) Blue, Green and Pink tubes were ok on this gear? Could someone shed some light on this? (Pardon the pun!)

My guess on this is that since Red and Gold tubes are solid colours (appearing same colour unlit) which the colour is a filter layer applied between the glass and white phosphor, similar to that of internally coloured GLS lamps. It could be possible that this makes the tube less conductive. If anyone is lucky enough to own a 2' 20w version of either tube, please let us know how it performs on ballast and starter switch. Upon switch-on, the starter closes and preheats the tube's cathode filaments. Upon opening, the magnetic field within the ballast collapses, causing a voltage pulse which strikes the tube. This is often repeated twice or more, causing the distinctive blinking at startup.">switchstart with a standard 155/500 or S10 type starter. Most 2' 20s in my experience fire up with very little intervention from the starter unless 155/200s or S2s are used! If a 20w Red or Gold is rather 'blink happy' then we have an answer! However, Paul and I did try a 4' 40w Gold in an SRS Atlantic and it fired up quite happily but a little slow!
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SuperSix
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Re: T12 Coloured Tubes And Starterless Gear?

Postby SuperSix » Fri Jun 17, 2011 2:39 pm

I've seen this in the Thorn catalogues too! :? I should think you're right about the coloured filter being slightly conductive, I've had issues with old MCFs and starterless gear in the cold and damp where the condensation creates a conductive film over the tube, the solution was to spray some silicone on a rag and wipe the tubes over with with it! :P

The only other things I can think of is either the phosphor composition of the red and gold tubes adds impurities to the gas filling which raises the starting voltage or the lack certain materials in the phosphor reduces the slight getter effect that the phosphor normally has and leaves impurities in the gas filling that would normally be absorbed.


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