(North America)

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Hello once again, as I continue to flood General Discussion with my username (sorry). It is common for ballasts here that power lamps that were never made in /RS versions to say either "Trigger Start" or "Preheat Lamp in a Rapid Start Circuit" (TS), and I understand that this is different than typical rapid start (RS) circuits, at least in the way that RS tubes have lower cathode heating voltage than preheat tubes, but are there any other differences?

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Known Facts:
 • Both TS and RS ballasts have some sort of current-limited high-voltage winding with appropriate specifications to strike the tube once heated, and run it once struck.
 • Both TS and RS ballasts have some sort of low-voltage windings with appropriate specifications to heat each filament.
 • RS ballasts have cathode windings on the primary side of the core, so that their voltage does not change when the tube strikes (constant voltage).

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Question:
 • RS heats each filament with a constant voltage that doesn't change even when struck. Does TS have this too, or does it have the filament windings with the main winding so that the heating voltage drops after striking (like European "starterless" autotransformers)?

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Thank you so much!
 

Trigger Start and Rapid star are identical from a ballast topology POV, the only difference is how many volts are supplied to the cathode, ~9V for Trigger-start and 3.6V for Rapid-Start

neither ballast normally reduces its cathode heating output after striking


the only ballasts to do reduce the cathode heating voltage after tube striking are British Quickstart systems, European starterless ballasts are almost always American Rapid-start type, or sometimes Semi-Resonant-Start or some form of switch-start with an integral thermal starter or the such like



you do also sometimes get funky hybrid Rapid-Start-Resonance systems like the Israeli Eltam 230V 50Hz F96T12/HO ballast, which is of a normal RS configuration but puts the cathode heating transformer *after* the series shunt-capacitor, this creates resonance between the capacitor and heating transformer primary, which boosts mains voltage going into the primary and choke, to facilitate the starting of an 8ft tube on normally 230V 50Hz OCV, it also boosts cathode heating power a bit during starting, but if there is a faulty tube, the continued high voltage can slowly cook the heating transformer (and there are some British 8ft 125W and 8ft 85W ballasts that combine resonance and the principles of RS or QS together like this also)

@LightBulbFun
Thanks so much! I wonder why they couldn't just call it RS instead, but whatever...

@LightBulbFun
Thanks so much! I wonder why they couldn't just call it RS instead, but whatever...

because "Rapid-Start" pretty much explicitly refers to a system or tube with 3.6V cathodes, so they call them Trigger-start to differentiate from this and make the user aware that it is *not* for 3.6V tubes, some ballast mfg's will say "Rapid-start" but preface it on the label that it is for preheat lamps again to tell the user, not for 3.6V RS tubes!

see for example https://www.lighting-gallery.net/gallery/displayimage.php?pos=-109581


not that many people seem to *realise* the importance of cathode voltages and that even 2 seemingly very similar tubes can have different voltages, and that bad things can happen if you make the mistake of interchanging them (especially if you put a 3.6V RS tube into a 9V system) I have seen quite a few people caught out by it, (I even once got 'conference called' into a gathering of lighting enthusiasts, who where at that point in time trying and failing to get a F40T12 magnetic rapid-start dimming ballast working, and I had to explain that it needed an RS tube, and once one was found (British market and many European F40T12's are 9V tubes by default, often only 3.6V if the etch explicitly states "RS" or the such like) it worked perfectly )

Many older references state that Trigger-Start ballasts do actually reduce power to the cathodes after ignition.  The windings for cathode heating are in series with the lamp, so after starting when lamp current drops, the cathode heat also drops.  In that respect the end result is same as the British Quick Start, but the actual ballast topology is still somewhat different.

Maybe later some companies used the TS name instead of RS?  But in the beginning it was definitely different.  In fact the reason John Aicher and Gene Lemmers at GE developed RS was specifically to improve on the TS system by further reducing end losses, along with reducing the troublesome arcing across the electrode’s leadwires at one end during preheating while the mains voltage was on the high side.

RS style circuits were popular in the USSR for some time around 1960's - 1970's. All the tubes in the USSR had 10V cathodes. May be except some rare niche use special applications ones I never seen. And all RS circuits were compensating. So in the American terms they should be called Trigger Start. Local name in use was 'бесстартерные' that is 'starterless'. A basic variant used a separate heating transformer with a primary winding connected across the tube length, so preheat voltage was dropped approximately two times after the ignition. Some circuits used extra tricks, resonance or so, to squeeze some extra OCV or compensating ratio.

I remember Soviet RS ballasts were somewhat troublesome. Ideally, a tube should have S-shaped ignition voltage vs preheat current curve, crossing actual OCV at some design point in the middle, but in practice many times the tube ended up with cold ignition, or worse just failed to ignite staying in preheat state forever.

I collected a lot of such ballasts which may have some historical interest today, but afraid these were lost because of some stupid actions of my lovely mother

Many older references state that Trigger-Start ballasts do actually reduce power to the cathodes after ignition.  The windings for cathode heating are in series with the lamp, so after starting when lamp current drops, the cathode heat also drops.  In that respect the end result is same as the British Quick Start, but the actual ballast topology is still somewhat different.

Maybe later some companies used the TS name instead of RS?  But in the beginning it was definitely different.  In fact the reason John Aicher and Gene Lemmers at GE developed RS was specifically to improve on the TS system by further reducing end losses, along with reducing the troublesome arcing across the electrode’s leadwires at one end during preheating while the mains voltage was on the high side.

very interesting! what sources are those? I have never heard of such a ballast, so I am rather intrigued, GE Catalogs of the 1950's dont mention any reduction in preheating voltage after striking, and the GE technical manual of 1970 does not either, just stating its the same as Rapid-Start

Ballasts are available to operate certain preheat lamps without using starters. These ballasts use the rapid start principle of starting and operation. They are designed around the characteristics of the preheat lamps involved. These ballasts are popularly called "trigger start" ballasts.

nor have I heard any American members report any reduction in cathode heating after striking, but I admit I dont know how many members here have explicitly checked for such mode of operation and I sadly do not have any American Trigger-start ballasts in the collection to test with!