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CFL ballast running F15T12

CFL ballast running F15T12

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It works! I harvested this ballast out of this dead CFL to see if I could do something with it - mainly, to make myself an instant start F8T5 setup. Of course, I had no idea if the ballast worked at all, but as you can see here, it does!

The way this ballast works is very interesting. When first powered on, the lamp doesn't glow, so all the power flows through the cathodes (enough to make them glow visibly, which is nice), then as the lamp runs up, the cathode heating is gradually reduced, eventually disappearing altogether once the lamp has started.

This is nice and all, but it poses a problem for lamps with one or no intact cathodes, which was my intention to run on this thing. With just the two main leads connected to lamp, nothing happens. I don't know if it's because the ballast actually doesn't provide the necessary OCV to instant start, or if all the power is running through the secondary leads until the lamp starts, or what. I need to do more tests. I do know the secondary leads aren't actually required once the lamp has started, as I can remove them and the lamp will stay running.

An F15T12 on this ballast results in a very slow, gradual, RS-like run-up, which is nice. However, the lamp is grossly underdriven, of course because the arc voltage is so much lower than a CFL. An F8T5 is driven perfectly.

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Light Information

Light Information

Ballast Type:Electronic rapid start

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Album name:themaritimegirl / Experiments, Projects, & Mods
File Size:260 KB
Date added:Nov 09, 2013
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Nov 09, 2013 at 03:37 PM Author: rjluna2
Nice experiment, TheMartitimeMan

Pretty, please no more Chinese failure.

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Nov 09, 2013 at 11:52 PM Author: Medved
The filament presence is necessary to not only complete the output resonant circuit (used to boost the voltage for ignition), but to close the oscillator feedback, so the ballast even operate at all.

This arrangement is part of the protection scheme of these ballasts: When the lamp cathode is not able to reach the emission, it first increase the heating power to it, till the filament break. And the broken filament then shut down the inverter, preventing from electronic damage and so potential fire. But necessary to say, this scheme proved to not work really properly under some cases (other lamp faults than emission coat wear, too robust filament,...), so the early CFL's (PLC-E from Philips,...) had a fire risk problem.

So to make it running for your experiment, you have to connect together leads belonging to each filament. But note, than this left the ballast without any cutout mechanism, so with no or completely dead lamp it will overheat within few seconds...

No more selfballasted c***

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