Electronics > Repair

DULUX S 11W Magnetic Ballast


I am looking for a replacement ballast for a desktop light. Don't grill me, I am fond of this light, because it was a present from my late mother in law, back in 1992. The light has developed a pretty strong flicker, which doesn't go away with three different old and new tubes. Looking at the construction, I only see the ballast as a cause for trouble.
The tube is an OSRAM Dulux S 11W, two pins, no heating filament.
The original ballast is a MagneTek 7911-3-1698E, for 7/9/11W lamps, using 230V 50Hz line power.
The ballast is directly inserted into the wall outlet and has two wires going to the lamp. One wire has a switch in series to the tube.

I have been searching for potential replacements ballasts, but couldn't find one for those Dulux S tubes without heating. I'd appreciate recommendations. I am not fixed on a wall-wart type of ballast, but would like to keep the lamp-head wiring in its current state.

Have you tried turning the ballast the other way around, so it is in the other mains lead? In general with PL9 lamps, avoid the Chinese made ones like the plague, because, to a lamp, they are all utter garbage. Try to find one made in EU, probably Poland, as they still make lamps there, or an older GE made in the USA. those ones made in the EU or USA work well, and last a long time. The ballast if it is a magnetic one rarely fails, it will fail short circuit and blow the lamp.

Otherwise you can get a small metal industrial case, a power switch and a pair of cable glands, and a 9W iron core ballast, and replace the existing one, but the plug in type is pretty much not going to be available.

There is a typical glowtube starter contained in the base of the bulb and any true magnetic ballast will work as long as the wattage is close and the line input voltage is correct. We use the PL9 bulbs as backlights in the older locomotive LCD displays. Are you sure the ballast is bad? They are simply a series inductor. You could measure resistance to gain a clue if it is bad or not. Perhaps a broken wire in the lead running through the mechanical arm from repeated motion.

SeanB, reversing L/N on this Class II insulated lamp didn't influence the flicker. No black magic. :)

CaptDon, thanks for your input. So the starter is integrated with the tube? Nifty. That explains how a simple inductivity is enough to operate the lamp. Your input gives me some homework. I will have to rig something up to test the wires and the switch. As so often, it is not about the complexity of the circuit, but about reducing collateral damage during testing. The ballast/cable-assembly is not built for maintenance.

Those FL9 bulbs work exactly like an F8T5 tube and basically the 'FS-5' starter glow tube is in the square part at the base of the bulb and is integrated with the bulb. So you get a 'new starter' with a new bulb so to speak. Those bulbs work easily with a series magnetic inductor on 120vac 60hz and at 240vac 50 or 60hz you just need and inductor with more reactance. The power factor is REALLY BAD!!
In the locomotives we run our bulbs at a much higher frequency from a small 74vdc to 150vac inverter board. the 150vac is to insure the bulb will trigger and light in cold weather. Some of our older models used F8T5 'Actinic' bulbs with bulb heating wires hand wrapped around the glass so the bulbs would not flicker in cold cab temperatures. The engines self start to stay warm 'A.E.S.S.' but if you turn off the cabin heat the temperature can still drop below zero F. (Alaska Rail, Chinese Mountains, Etc.)


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