Philips TL-S tubes

[mocha]

Hey all,

Anyone here have any old school knowledge about ballast-free florescent lamps?  Specifically I'm talking about this lamp which was still on the market up until about 15 years ago.

https://www.assets.lighting.philips.com/is/content/PhilipsLighting/comf2571-pss-global

We still use this lamp on an old rail vehicle in a 600 VDC series circuit with dropping resistors.  Someone told me that in the old days the tribal knowledge was to occasionally switch the polarity of these bulbs or else the mercury would migrate and they stop working.  I need to try this on some of the 'bad' bulbs that we have.

We'll probably start looking at low voltage LED strips as a replacement.  Anyone know anything else about these old style tubes?

[SeanB]

They have that external starter strip, which basically enables the beginning of glow discharge without high voltage to start, or a preheat. You can emulate it with a strip of copper tape down the outside, but it only works on the T12 tubes, not the T8 or smaller ones. Yes flipping the lamp around helps even out the stripping of the cathode from being run as an anode, and being bombarded by the electrons, and at the cathode end being bombarded by the mercury ions.

Replacing with LED tubes is probably the only way, using 2 in series on the 600VDC rail, and using 230VAC tubes, which you will need to order from the EU, or direct from Osram China. Leave the ballast resistor in place, it will help with keeping the spikes out of the lamps, and will limit current if a lamp fails. You will need to place a 1A fuse in series with the 2 lamps for safety as well, but it all can still fit in the original gear trays and not need much work, other than replacing the R18s sockets with regular lamp sockets. That will allow you to do the rework in sections.

[mocha]

Sounds like you have a lot of experience with florescent tubes!  I guess this was the old school knowledge that's been mostly lost along the way because even the people in rail don't know much about this stuff anymore.  In our case I think we will convert the circuit to low voltage 36VDC LED strips with a minimal controller, it's also desirable to get the 600VDC out of the passenger compartment. Thanks.