I have a Rayton R3 UVB lamp for phototherapy. It consists of a this PL-S 9W/01/2P bulb with a G23 base, and the ballast is magnetic 120v/60hz.

I would like to swap the ballast for a 240v/50hz ballast, and all I've found is a universal electronic ballast (here) but Wikipedia and others say that two pin lamps are designed for conventional (magnetic) ballasts. Does that mean that an electronic ballast should not be used? Can you tell me if the linked ballast is compatible?

  • If it says it works with two-pin lamps, it will work with two pin lamps. Commented Oct 4, 2018 at 6:40
  • They make electronic ballasts for high pressure sodium lamps. The ballasts are primarily sold by "horitculture" shops, you know, the ones where 95% of the gear they sell is used to grow pot. If they make electronic ballasts for HPS, they gotta make it for anything. Commented Oct 4, 2018 at 7:43
  • @SomeoneSomewhere that only applies if the product is any good. Noname ballast from eBay, I would not get my hopes up. Commented Oct 4, 2018 at 7:50
  • @Harper Mis-listing is pretty common, but in this case they also show images of it hooked up to a two-pin socket, and it doesn't have enough terminals for a four pin. OTOH, it doesn't say anything about supply voltage and uses US colours... Commented Oct 4, 2018 at 8:03

3 Answers 3


The given phototherapy tube is a glow start tube with filaments. The glow starter is built into the base. Glow start tubes are usually driven with conventional magnetic ballasts. There might be also electronic ballasts for 2 pin tubes with built in glow starters, but usually electronic ballasts need access to all 4 pins of the tube.

The given listing for "universal electronic ballast" is lacking in details (input voltage/frequency ranges, tube current etc.) to give any recommendation for it's suitability.

I'd recommend replacing the existing ballast with an European model. For example: http://www.lighting.philips.com/main/prof/lighting-electronics/fluorescent/fluorescent-electromagnetic/bpl-em-ballasts-for-cfl-pl-t-pl-s-and-pl-c-lamps/913710122350_EU/product or https://www.helvar.com/en/products/L11D240V50Hz/ or any other magnetic ballast with correct frequency, voltage and lamp power. Also when converting the wires might need also upgrading for the higher mains voltage. Consult a local lamp repair shop for advice.

Added, since unable to comment:
Suitable search terms to try on your favorite online platform: "magnetic ballast 9w" "Helvar L11D" "pl-s ballast".

  • Thanks. I'm having a hard time locating a retailer online for that item. Could the cheap one from ebay (assuming it nominally matches the spec) damage the tube or just fail more quickly? Commented Oct 4, 2018 at 19:21

Fluorescents are arc-discharge lights, meaning like neon where a high voltage runs the length of the tube, and that arc must be initially struck on startup. 2-pin simply means the lamp does not have electrode preheaters for gentle startup. They are built extra tough to handle this.

So a 2-pin ballast needs a somewhat higher startup voltage. That is not a significant difference, if anything it makes the ballast simpler than a preheat ballast. So yes, it can easily be an electronic ballast.

For instance you see the same dichotomy on 48" fluorescent tubes, rapid/programmed start ballasts use the preheaters, instant start ballasts do not. Both are electronic.

Once the arc is struck, the tube needs something to limit current. That's tge other job of the ballast, and why they call it a ballast. Again not a problem to do that in an electronic ballast.

Getting rid of buzz and flicker is still desirable, so I'm sure somebody makes an electronic ballast for your types of bulb.

Not sure I would trust a no-name ballast brand from eBay, though. I would gravitate toward companies with an actual history at making ballasts, like GE, Philips/Advance, Sylvania and others often seen on sites like 1000bulbs.com.

  • Is a problem with a no-name ballast that it might fail quickly, or that it will damage the tube (no warmup etc) Commented Oct 4, 2018 at 19:19
  • 1
    @afuna no-name items sold on ebay are generally the low end of what is sold on Alibaba, and are extremely cheaply made items made in a certain country specifically for export to suckers. So yes, any of those consequences, or the unit bursting into flame; or making RF hash so your radio/TV, Bluetooth, or Wifi degrade; you name it. They are not legal for retail sale in this country and they are using ebay as a loophole to effectively sneak em by all the UL and FCC standards and FTC oversight. Commented Oct 4, 2018 at 19:53

I know in the early 2000's the U.S. outlawed magnetic ballast the universal ballast is based on voltage they use 100-277v where the old mag ballast have a specific voltage 120v, 240v,277 as a common in the US now all 3 of these if the same lamp type use 1 type of electronic ballast. You do need to match the ballast type with the lamp if not sized properly the lamp or the ballast will have a shortened life span. The hospital I worked at used some photo therapy (in Oregon) for SAD treatment and we also had white light fixtures with the g23 base that we converted to electronic ballast. Don't go cheap I know the early electronic ballast were a high failure rate item but still find the failure rate high on electronic ballast if not a quality brand compared to the old magnetic ballast that lasted for decades.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.