The mystery of the intermittent fault on flourescent light

[The Ghost]

So I was called again to look at light in unit that has gone off. Of course when I got there it was on (again) The circuit is very straight forward, supply from Merlin Gerin DB 10a MCB supplying four twins. Checked all the connections for being tight including switch (wiggled and pulled) and securely fixed into termination points, all ok. Checked cable down to light from klix rose, ok. The fitting is HF with TriPhos tubes. The light stays on during this process no flicker.
So I have checked the cabling from the MCB to first light (which is the one with intermittent fault) and checked onward to the last light, four in all. No loose connections, all lights are working except this one, occasionally does not. As you may divine from the picture below it is not a situation (20 feet up) that lends itself to popping up with a tester and having investigations without a tower which is considerable expense. The cable (singles) is in plastic trunking changing to 20mm conduit as it progresses to each light. There is no sign of damage to the cables I can access, and have fought shy of putting up a tower due to cost and the landlord being a very very frugal person to put it charitably. Any ideas of a brilliant nature welcome.

 

[static zap]

Lamp changed / cabling not , logically must be in that little bit of cabling.
Phantom enamel painted copper ..
(do they have a night shift - and a fussy sod who hates fluorescent lighting)...even though its HF!

 

[elsparko]

Lamp changed / cabling not , logically must be in that little bit of cabling.
Phantom enamel painted copper ..
(do they have a night shift - and a fussy sod who hates flurescent lighting)...even though its HF!

those baylights can be annoying if they are in the corner of your vision lol

 

[KEV 1 N]

Unlike a choke, which is simple and usually either works or doesn't, an HF ballast is an electronic switched mode power supply, containing many dozens of components (some of which have finite lifespan)

Got some Chryselco 5foot flossys in my loft which my Grandad got donkeys years ago (which were probably old then), they must be 50 odd year old, still working with the Warm White Crompton lamps he got them with and the old aluminium case starters!

 

[Jim90]

Got some Chryselco 5foot flossys in my loft which my Grandad got donkeys years ago (which were probably old then), they must be 50 odd year old, still working with the Warm White Crompton lamps he got them with and the old aluminium case starters!

Surprise the Feds haven't kicked your door in for the lack of snow on your roof in winter!

 

[DPG]

Putting it rather simply, there can only really be two causes:

a) Unreliable supply of electricery to the wires feeding the fitting
b) faulty fitting

You can prove a) by doing suitable testing, but as said above it would need an access tower ideally. I'd at least rope the ladder to the top girder and get someone to foot it at the bottom if not.

You can eliminate b) by changing the fitting - it's possible you have had the initial faulty unit, and then a dodgy replacement.

 

[KEV 1 N]

Surprise the Feds haven't kicked your door in for the lack of snow on your roof in winter!

Haha! My roof usually retains the snow (well insulated) although a few of the neighbours doors require kicking in for "further investigation" due to lack of snow on their roofs!

 

[ipf]

I remember that the very early tubes had an earthed conductive strip along their length to aid starting. I suppose the same capacitive effect is achieved now by internal coatings and the proximity of the tube to its earthed fitting. So check too the connection of the cpc to the fitting, the continuity of the cpc back to the DB and that the reflector is electrically connected to the cpc.

Was that around about the time you were pioneering with radio?
...and that's why some called them 'strip lights', maybe

 

[Marvo]

If I had to work on that ladder I'd be looking for the easiest way out so disconnect ballast and fit LED tubes.

 

[ruston]

I have just done that for the first time this week on a showroom sign.
Up to now I am impressed with them.

 

[westward10]

Absolutely agree there! I have a youngman tower and will be using it for any further access. Just used the ladder wedged at the bottom for a quick look at the fitting adjacent to the faulty light.

Once is enough to become a statistic.

 

[The Ghost]

Once is enough to become a statistic

I so agree.