Intermittent problem with 70w son luminaire

We use a 70w Thorn son luminaire to light the front of the house and the pathway to the front door. This isn't a security measure, it's just to help folk get to the front door after dark. The luminaire has an in-built twilight sensor but is also controlled by a time switch. This time switch is set to turn the luminaire off between midnight & 05.00. Recently the lamp has sometimes not been coming on at dusk. I have fitted a new lamp and ignitor but the problem remains. I have also tried taking the time switch out of the circuit but this makes no difference. As far as I am aware the problem is, therefore, with the ballast or capacitor. Any ideas which please? Many thanks Nick.

Reply to
Nick
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The only person that can find out is you. I'd start by testing for juice at the SON fitting, to differentiate between light fitting problem and supply problem. Of course you need to have the fault hapen while youre metering it: prodding the wires about usually manages to provoke something. BUT choke ballast lights can produce lethal voltage spikes when disturbed like this, so proper care and competence is necessary.

So, it could be: choke cap ballast to lamp wiring bulb holder wiring in the ballast box mains supply cable switch mcb/fuse ... thats if the new parts arent defective.

NT

Reply to
bigcat

NO! If this is a SON with external ignitor as suggested, the ignition pulse will destroy just about anything you connect to the SON fitting, and possibly you too.

Check mains supply is OK (try an ordinary 100W lamp on the supply, not in the SON lampholder). You didn't indicate if you had tried bypassing the photocell, which would be worth checking. Other than that, I can only suggest substitution of the ignitor and the ballast. (Funny, I didn't think 70W SON's used an external ignitor, but I may well be wrong. 250W ones certainly do as I have a couple.)

Was the old lamp dead (darkened arc tube, and cycling on and off every minute or so)? This can burn out poor quality ballasts, and it probably doesn't do wonders for the ignitor although I've not had one of those fail.

Actually, the capacitor will not affect lamp operation, just power factor and current drawn, so you can probably rule that out.

Reply to
Andrew Gabriel

70 watt SON lamps are available in both internal and external ignitor versions. A lamp with internal ignitor will give problems when used with an external ignitor (flashing).

There is some incompatability between manufacturers of SON lamps and the associated gear (ignitor, capacitor and choke). The OP may have obtained a lamp and gear which are not compatable. The symptoms range from a flashing lamp to a failure to ignite. Best to use lamp and gear from the same manufacturer, or seek their advice.

Jason

Reply to
Jyestyn

Many thanks for all the helpful replies. I have checked the mains supply, it's good. I have checked (and bypassed) the photocell. Supply to the control gear is good in both cases. This is definitely external ignitor. We use a few of these and also some with ignitor internal to the lamp. The old lamp wasn't dead. The internal wiring appears to be ok. As the problem is intermittent I am inclined to think it is a problem with the control gear. Given Andrews' comments on the capacitor I will try changing the ballast.

Thanks again Nick.

Reply to
Nick

Are you thinking I meant meter at the bulb holder? I meant meter at the mains input to the control gear. I wouldnt recommend messing with 1kv+ while the things powered up.

NT

Reply to
bigcat

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