Installed new 3-4 years ago. Controlled by photocell dusk-dawn.
Lamp originally supplied was double ended Osram HQI-TS 70W/NDL.
Couple of weeks ago noticed that the light output was considerably down.
Ordered replacement lamp from CPC and received Osram Powerstar HQI-TS
Excellence 70w/ndl.
New lamp slightly different in the tubular ends but otherwise very similar.

Installed new lamp and, at dusk, all hunky dory. Light output very much
improved.
A few days later the lamp turned on at dusk and turned off after about 5
minutes. Then flickered for about five minutes, ignited and stayed on all
night.
It now does this every evening.
The photocell is remote from the luminaire and is not receiving light from
the luminaire or elsewhere.

My immediate thought was a duff lamp but this is probably not so as it
re-ignites and continues to burn constantly until dawn (this verified by
observation and cctv).
The same process makes me think that the control gear is working correctly.
So I'm thinking that the problem lies in the differences between original
and replacement lamps, which appear to be very minor.
Unfortunately I have no way of testing any of the components other than by
replacement.
Worries me a bit that the flickering may damage components.

Any thoughts on what the problem may be and how to fix it?
Thanks,

Nick.

In article ,
"Nick" writes:
Installed new 3-4 years ago. Controlled by photocell dusk-dawn.
Lamp originally supplied was double ended Osram HQI-TS 70W/NDL.
Couple of weeks ago noticed that the light output was considerably down.
Ordered replacement lamp from CPC and received Osram Powerstar HQI-TS
Excellence 70w/ndl.
New lamp slightly different in the tubular ends but otherwise very similar.

Installed new lamp and, at dusk, all hunky dory. Light output very much
improved.
A few days later the lamp turned on at dusk and turned off after about 5
minutes. Then flickered for about five minutes, ignited and stayed on all
night.
It now does this every evening.
The photocell is remote from the luminaire and is not receiving light from
the luminaire or elsewhere.

My immediate thought was a duff lamp but this is probably not so as it
re-ignites and continues to burn constantly until dawn (this verified by
observation and cctv).
The same process makes me think that the control gear is working correctly.
So I'm thinking that the problem lies in the differences between original
and replacement lamps, which appear to be very minor.
Unfortunately I have no way of testing any of the components other than by
replacement.
Worries me a bit that the flickering may damage components.

Any thoughts on what the problem may be and how to fix it?

This is really strange. One thought is poor lampholder contact,
triggered as it heats/expands, causing the arc to extinguish until
the lamp cools enough for the igniter to restrike it.

Another thought - have you got any equipment which might generate
voltage sags, such as a large motor starting? That might extinguish
the arc.

There is a note on Osram's technical information
http://osram.com/_global/pdf/Profess.../106T001GB.pdf
that operation of HQI-TS Excellence at PT-TS ballast - which
are not produced or sold anymore for very long time - is
not permitted. You might want to check what the type of
ballast is.

Copying sci.engr.lighting

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Have you thought that the previous lamp may well have not been the problem
but the internal circuit instead?

Brian

--
Brian Gaff -
Note:- In order to reduce spam, any email without 'Brian Gaff'
in the display name may be lost.
Blind user, so no pictures please!
"Nick" wrote in message
...
Installed new 3-4 years ago. Controlled by photocell dusk-dawn.
Lamp originally supplied was double ended Osram HQI-TS 70W/NDL.
Couple of weeks ago noticed that the light output was considerably down.
Ordered replacement lamp from CPC and received Osram Powerstar HQI-TS
Excellence 70w/ndl.
New lamp slightly different in the tubular ends but otherwise very
similar.

Installed new lamp and, at dusk, all hunky dory. Light output very much
improved.
A few days later the lamp turned on at dusk and turned off after about 5
minutes. Then flickered for about five minutes, ignited and stayed on all
night.
It now does this every evening.
The photocell is remote from the luminaire and is not receiving light from
the luminaire or elsewhere.

My immediate thought was a duff lamp but this is probably not so as it
re-ignites and continues to burn constantly until dawn (this verified by
observation and cctv).
The same process makes me think that the control gear is working
correctly.
So I'm thinking that the problem lies in the differences between original
and replacement lamps, which appear to be very minor.
Unfortunately I have no way of testing any of the components other than by
replacement.
Worries me a bit that the flickering may damage components.

Any thoughts on what the problem may be and how to fix it?
Thanks,

Nick.

snip

Any thoughts on what the problem may be and how to fix it?

This is really strange. One thought is poor lampholder contact,
triggered as it heats/expands, causing the arc to extinguish until
the lamp cools enough for the igniter to restrike it.

Another thought - have you got any equipment which might generate
voltage sags, such as a large motor starting? That might extinguish
the arc.

There is a note on Osram's technical information
http://osram.com/_global/pdf/Profess.../106T001GB.pdf
that operation of HQI-TS Excellence at PT-TS ballast - which
are not produced or sold anymore for very long time - is
not permitted. You might want to check what the type of
ballast is.

Copying sci.engr.lighting

--
Andrew Gabriel

Thanks very much,
lampholder contact is good, or at least as good as it gets with this type of
lampholder. I have checked and there is no sign of
arcing/burning/degradation to the contacts. The spring mechanisms that hold
the lamp are good.
There is no equipment on this supply that could generate any major voltage
sag.

I had not seen the note on Osram's tech info. Will check the luminaire over
the w/e.
I suspect this may be the problem. If so and depending on availability/cost
of replacement ballast, it may be preferable to replace the luminaire.

Nick.

"Brian Gaff" wrote in message
...
Have you thought that the previous lamp may well have not been the problem
but the internal circuit instead?

Brian


Thanks Brian,

I have tried the previous lamp in an identical luminaire (on the bench) and
it shows exactly the same characteristics. Strikes immediately with light
output very considerably reduced (40% ish). Have tried this for several
hours.
The replacement lamp strikes immediately and extinguishes after a few
minutes. It then has a few minutes stuttering and will strike. It continues
to burn perfectly for twelve hours or so until the photocell switches to
off.
Your comments on the internal circuitry are perhaps quite relevant given
Andrew Gabriel's response in this thread.
My thoughts a
The original lamp has had its day.
The replacement lamp may not be compatible with the gear in existing
luminaire.
Try a new lamp of the same kind as the replacement.
Check the gear in the luminaire. If necessary replace some or all.

Thanks for your response,
Nick.