Thorn 40W Deluxe Warm White I.R.S. 4ft T12 ignition metal striped fluorescent tubes

I had mentioned in the comments of a previous upload of mine that there was a lamp wholesaler which I had visited previously that had some Thorn IRS tubes on the shelf, which I figured I should go back for so as there where these tubes and some others I wanted ((to rummage through all the 8ft tubes I had to leave behind previously) I made arrangements and went back to that wholesaler to have another look at these tubes and well I am glad I did, I had a closer look and saw they where not just Thorn IRS tubes, but in Deluxe Warm White too! so I of course had to have the lot, could not let those get bought and used by some random punter!, I also may have purchased way too many other lamps again like my previous visit, but those will be an upload later in time (I still have many lamps and tubes from my first visit to upload!)

Thorn IRS (Internal Resistance Start) tubes are equivalent to Philips TL-M tubes, which is to say, they are Rapid-start specification tubes (3.6V low resistance cathodes) with the addition of an externally applied conductive stripe that is electrically connected to one of the tube pins via high ohmic resistor usually in the order of 1M-2M ohms (I measure just under 1M for these tubes) a picture of the setup can be seen here

this arrangement has the same sort of effect that the ignition probe in a mercury lamp in helping the lamp strike, especially when there is no earthed metal work near by that is normally required by RS tubes on RS control gear

of note in the inset photo of the lamp cap is the punch-lock indented in the end cap above one of the pins, that connects the resistor from the tube pin its connected to, to the lamp cap shell which then has the stripe painted on it going the length of the tube, thats one of the fun things about these IRS/TL-M type tubes is every manufacture has a different way of doing this resistor setup :) also along those lines (pun not intended!) the starter stripe, its composition/construction can often vary, I have heard that these striped tubes where a bit of a pain for manufactures, with problems of making a stripe that could be easily/inexpensively applied to the tube during production, which was also durable well bonded to the tube

it should be noted on the subject of the stripe, that another classification of very similar looking striped tube exists the British MCFA tube also known as the TL-A tube, here the tube has the same sort of stripe, but it is *not* connected internally, and instead the stripe must be connected to earth/ground and then it performs the same function of an ignition aid for when the tube is used on starterless control gear, MCFA/TL-A tubes also have 9V high resistance cathodes, and because of this difference in cathode voltage/resistance the 2 must not be interchanged when Quickstart or Rapid-start control gear is concerned, IRS/TL-M/RS tubes are for Rapid-start circuits only and MCFE/MCFA/TL-A are for Quickstart circuits only (but the types can be interchanged on SRS control gear and Switch Start control gear)


I have not had a chance to light one of these, but I notice through the rather thin phosphor coating at the other end they are interestingly equipped with cathode guards, and I do look forward lighting them eventually being Deluxe Warm White, I am of course quite interested to look at their spectrum and see how they compare to other Warm White Deluxe type tubes like Philips Colour 32 :) (although sadly I dont currently have any other WWX tubes to compare with other than a couple Philips Colour 32 tubes in my collection, I would certainly not mind getting some WWX tubes from Osram-GEC and the USA to compare with as well) speaking of the fine details I also note the sleeves curiously do have the colour of the tubes marked on them, this is pretty unusual for Thorn, normally their sleeves are almost completely generic and betray no information about what the actual tube contained with is!