hi, i’ve got a Sylvania 85w T12 6ft fluorescent tube (don’t know how it ended up here in italy) and i was wondering how can i run it since i don’t have any specific ballasts for it. thank you very much

Have you got any gear around that sort of wattage?

If you can find out the voltage and current, you can calculate the appropriate ballast inductance and get a ballast wound at a transformer winding place.
Alternatively, see if someone has a ballast and an inductance meter.

I have some 100w ballasts for t8 tubes, those are approximately 0,4 henry, so you're probably looking at 0,5H of inductance.

I bet that current/voltage ratings are close to 80W European tubes, so two 36/40W chokes in parallel may be approximately ok, BUT these are marked as rapid start and so may have trouble to start in preheat mode with a starter because of low-voltage low-impedance filaments. American friends know probably better.

Also there are some obscure high-current electronic ballasts for very high wattage CFLs, capable of running tubes at ~0.86A required. Probably will not preheat the tube properly too, but at least should start it in cold-start mode.

hi, i’ve got a Sylvania 85w T12 6ft fluorescent tube (don’t know how it ended up here in italy) and i was wondering how can i run it since i don’t have any specific ballasts for it. thank you very much

you say 85W T12 6ft tube, but there are 2 distinct types of that tube, so I have to ask which type is it?

there is the US F72T12/HO Rapid-start tube with R17d caps, and then there is the British 85W 6ft T12 Bi pin tube primarily designed for switch start and SRS circuits (the IEC spec sheets dont even list a 3.6V RS spec of that tube)

the 85W T12 6ft bi-pin tube is designed to run off an 80W mercury lamp/5ft 80W T12 ballast, so thats what I would use if you have it, if you dont have such a ballast then as RRK says a 2x36W/40W 4ft chokes ganged together will work well, you will likely need an S16 starter, a traditional S10 type starter might keep re-triggering (tho you can just remove it once the tube cathodes have come up to temp)

the US tube is designed for rapid start circuits mainly, so if you have a suitable cathode heating transformer thats what I would use in conjunction with an aforementioned 80W choke or 2x36W chokes (the british and US tubes both run at 800mA more or less) a switch starter will work, but as RRK mentioned it might be a bit sluggish to get going because of the low resistance 3.6V cathodes

would I be right in saying you have a US spec tube? I say this because, the British 6ft T12 was fairly quickly re-rated to 75W and thus most 6ft T12s are 75W or dual rated 75W/85W, and I have never seen a Sylvania T12 6ft 85W *only* tube in British spec (by the time Sylvania became a known entity here in the UK 85W only tubes had mostly ceased to exist)

it’s a british one i would say, normal G13 endcaps and only rated 85W (the model is F85W/CW)
thank you all for the replies fortunately i both have 36/40W fluorescent and 80W mercury choke

thats very interesting! I hope you do an upload of it, as mentioned I have never seen a Sylvania 85W only 6ft tube, all have been 75W/85W etc I am quite pleased to hear I am wrong in my assumption here!


and just to confirm you are sure the tube if 6ft long and not 8ft long? 8ft 85W tubes also existed here (but they have very different electrical parameters (do not run one of those on an 80W mercury choke!)

i’ll update you tomorrow since i don’t have it between my hands now. it also may be a strange tube since the rack were i found it said “85W 150cm” so it may be a strange size but i just assumed it was a mislabeling but i didn’t have time to check whether it’s 180cm or really 150cm (in that warehouse multiple things are mislabeled, such as ballasts labeled as rheostats)

I am certain you would definitely notice you are carrying 180cm tube, as it is *extremely* bulky even compared to 150cm one...

i’ll update you tomorrow since i don’t have it between my hands now. it also may be a strange tube since the rack were i found it said “85W 150cm” so it may be a strange size but i just assumed it was a mislabeling but i didn’t have time to check whether it’s 180cm or really 150cm (in that warehouse multiple things are mislabeled, such as ballasts labeled as rheostats)

it’s not 1.80m it’s 1.5m 
what kind of tube is this?
here’s it lit on a 65w ballast