I wonder if A US preheat fluorescent fixture can be retrofitted to LED by using a European market LED tube that uses a LED starter?

On one of the UK light sites, someone said those 'LED starters' are nothing more than a fuse in a starter case.
On a 3' or 4' US fixture I see no reason it wouldn't work.
On a 2' or less, the only thing I'd question is if the 120v/240v OCV would make a difference with the LED tubes?...

They are indeed just a fuse link in a starter case, and depending on voltage of the fitting, ( not sure about US battens), the tubes are designed to run on both 50 and 60 Hz. Pictured here is one of 135 LED tubes that I fitted to our massive showroom sign at work.

Fuse ? Last one i peeked into (through the hole between the terminals) had just a steel staple inside..

Overall this might work (using the ballast more or less as a transformer), but with a few places for trouble :



LED tube connection :

There are generally 2 connection schemes for LED tubes...

The "safe" type : Input to LED circuit is from 2 pins on one end of tube. The 2 pins on other end of tube are shorted. This tube requires the "LED starter" to complete the circuit (to bring one of the supply poles through the shorted end of the tube, starter wiring)

The "chinese" type : On each end of the tube the 2 pins are just shorted together, the LED circuit is powered between the 2 ends of the tube. This tube requires the starter to be just removed. Using this tube with a "LED starter" will cause a stuck starter condition on the ballast



Starter compensation in US Preheat ballasts :

In some US ballasts ("2 lamp" etc) the starter loop for one of the lamps doesn't just go end to end of the tube itself, but it goes through a winding in the ballast. In a Fluorescent setup this was done to correct the preheating current. With a LED tube this will just change the voltage supplied to the tube (i dont know in which direction of change)

Also, the compensation winding might be too thin to handle continuous current (it was meant to pass current only for a few seconds at a time), even with the current of the LED tube which is less than the FL tube by a factor of 4 or so (x2 due to ~200+ V operation voltage vs. 103V of F40T12, and x2 due to the tube's power being half that of the FL tube)



LED tube failure modes :

Inside the LED tube, the input goes to a rectifier bridge and the input of a switching power supply (that might be one of few types). The power supply could fail in a few ways, that will result in just a BANG when powered from 230V directly, but can instead go into a burning/melting sort of fault when the input current is limited by a ballast. This can happen also with the European choke ballast

The concern is, that such failure modes can also damage the ballast itself, especially if a diode in the rectifier bridge fails and the tube becomes a half wave load. Also, burning up power supply (which is inside one of the ends of the LED tube) could damage the socket of the FL luminaire

Some are fuses but most are exactly that, just a brass staple inside, I usually just cut the glow bottle out of the existing starter, and twist the wires together on the suspension capacitor!

Also dont use it on a two lamp ballast. These tend to wire the lamps in series, but the SMPS wired in series yield very unstable, wildly flashing setup.