Electric Fly killer

[pennychew]

Evening all

I have a fly light to repair from my mates shop that i'm having a bit of bother with, thought id post it up in here and see if i can learn something!

Its a 2 x 36watt Genus spectra fly light, the light was reported as not working one day, no idea if one tube went off first or if it just stopped altogether. I pulled the fuse from the switch fuse spur and checked it.... it was fine so i put it back in and switched the spur back on, both tubes tried to light then flickered and went off. I turned the power back off then on again with the same result. I took it down and brought it home to have a play with.

Upon opening it up there is basically just an electronic ballast and two 36watt tubes, i assumed since the tubes were almost flickering into life they were probably ok? i took the ballast into my local wholesaler and they sorted a new tridonic one out for me which is the same pin configuration but slightly different size, anyway put the new ballast in and it was exactly the same so its probably the tubes, before i start ordering tubes i'd like to know how to test the outputs from the ballast and also if you can test the tubes with a meter or not?

Any advice appreciated as im interested in learning more about how they work and how to fault find not just looking for someone to fix it for me if you know what i mean!

Thanks!

Stu

 

[pennychew]

Not sure why one of my photos is supersized either?

 

[telectrix]

hmm. i have a similar unit. both tubes were definitely gone ( black as soot at ends). replaced both tubes and it don't work. not got round to further investigation, but any tips floating about will be acted on ( one day ).

 

[pennychew]

Thanks Tel, if i find out its not the ballast at fault i'll send you one down to try in your light mate

 

[Marvo]

It's possible the two 36w tubes would be sreies configured off the ballast so if one tube goes South the other will also stop working. I'd definitely replace both tubes together though.

These newfandangled ballasts are a tricky beast, they have intelligence built in that monitors current draw, ignition times and phase angles to establish the condition of the tubes at all times. With tubes that are failing or completely faulty tubes or when no tubes are connected the ballast will automatically shut down the output which makes them a bugger to test because you need to simulate healthy tubes to get an output. The idea is to prevent fires, ballasts used to have a nasty habit of bursting into flames when the had failed tubes for long periods of time.

 

[pennychew]

Thanks for that marvo, when i get a chance im going to rig up a a couple of normal tubes i think i have lying in the loft to the original ballast and see if they fire up

Stu

 

[Marvo]

That's probably the best way to go, you can test the ballasts using standard straight linear tubes as long as they're similar wattages. I'd avoid your tester on the ballast output, the supply to the tubes is modulated and it won't be a sine wave structure so it's doubtful your tester will give you any meaningful readings.