Thorn Fluorescent With Slickstart

[securespark]

Hi guys

Wonder if you could shed any light on this issue?

I have a customer with three 5' flu's in the garage. They are all elderly Thorn fittings with slickstart modules rather than starters and they are all fitted with 58W tubes.

The problem is that the tubes do not fire up properly. On initial switch on,one end of the tube will glow, but no more. If you fiddle with the switch and turn the supply on and off several times in quick succession, the will fire up as normal. Also, the tube ends are running extremely hot.

I have noticed the choke is labelled as 80W. Is there a possibility that the new tubes (having a lower wattage) in conjunction with the slickstart are not compatible, or is it just a case of dodgy lamps?

I have asked the customer to buy a new one to try as all the tubes at the property have discoloured ends. Can't believe all three fittings are dodgy.

Voltages coming in to the fittings are all within the expected range.

Can anybody help me please?

 

[bernardgreen]

I recall from way back that gear without starters needed special tubes that were different from those used in fittings with starters. Whether it was more mercury vapour or a conductive strip along the tube I cannot remember.

Before striking both ends should glow dimly as heaters heat up their cathodic coating. Blackened ends suggest the coating has all gone and the tubes will be difficult if not impossible to strike.

 

[ericmark]

Seem to remember the tubes are thicker. Think the only place I found them local to me was Wickes. Last lot did not have earth strip down tube and still worked.

 

[securespark]

So you think they need special tubes?

Maybe I'll try and clear it up with a phonecall to Thorn.

 

[bernardgreen]

I wonder if Slick start is a variation of Quick Start which Thorn invented.

Does the ballast "choke" have 4 terminals ?

If yes then this might apply and the difference is T8 or T12 tubes

http://en.wikipedia.org/wiki/Fluorescent_lamp ( simpliest source to quote )

Semi-resonant start was invented by Thorn Lighting for use with T12 fluorescent tubes. This method uses a double wound transformer and a capacitor. With no arc current, the transformer and capacitor ring at mains frequency and generate about twice mains voltage across the tube, and a small electrode heating current.[17] This tube voltage is too low to strike the arc with cold electrodes, but as the electrodes heat up to thermionic emission temperature, the tube striking voltage reduces below that of the ringing voltage, and the arc strikes. As the electrodes heat, the lamp slowly, over 3–5 seconds, reaches full brightness. As the arc current increases and tube voltage drops, the circuit provides current limiting.

Semi-resonant start was mainly used in commercial installations because of their higher initial cost. There are no starter switches to be replaced and cathode damage is reduced during starting. Due to the high open circuit tube voltage, this starting method was particularly good for starting tubes in cold locations. Additionally, the circuit power factor is almost 1.0, and no additional power factor correction is needed in the lighting installation. As the design requires that twice the mains voltage must be lower than the cold-cathode striking voltage (or the tubes would erroneously instant-start), this design can only be used with 5 ft and longer tubes on 240 V mains. Semi-resonant start fixtures are generally incompatible with energy saving T8 retrofit tubes, because such tubes have a higher starting voltage than T12 lamps and may not start reliably,especially in low temperatures. Recent proposals in some countries to phase out T12 tubes will reduce the application of this starting method.

 

[Spark123]

The quickstart don't work with slimiline tubes, you need to have normal ones i.e. 65w ft ones.
They can also be a bit awkward to get started in the cold.

 

[333rocky333]

As stated you need 65/80 watt T12 tubes, inch and half diameter.

You may note a capacitor in series with one of the lamp leads,sometimes a temporary fix is to take out that capaciter, and the 58 watt tubes sometimes strike, but thats not ideal.

58 watt tubes usually can only be replaced into them older fittings if they were switchstart (starter fittings)

 

[securespark]

Thank you guys!

I can now inform the customer he is indeed using the wrong lamps.