Fluorescent tubes with electronic ballast

I have a bathroom mirror with two 18" 15W fluorescent tubes inside, similar to http://www.argos.co.uk/static/Product/partNumber/4327411.htm
A couple of days ago, one of the tubes didn't come on. I took the front off and swapped the tubes over in order to try to ascertain whether the problem was with the tube itself, or with whatever was powering it.
The effect of swapping the tubes was that *neither* of them now works - and they continued not to work when I swapped them back!
The tubes are driven by some sort of electronic ballast which has mains in at the top and 8 outputs at the bottom - 2 for each end of each tube.
Do any of you have any experience of these things? If a tube fails, can that kill its side of the ballast? Could swapping the tubes have killed the other side, too?
Is there any way that I can test a tube by using a multi-meter? I've tried measuring DC resistance across the pins. On both tubes, there appears to be virtually no resistance between the two pins at the one end and infinite resistance between the pins at the other end, but I'm not sure what - if anything - that tells me!
Would the best plan be to replace the ballast and both tubes? I can't find an identical ballast but this one is similar and would probably fit: http://www.nationallampsandcomponents.co.uk/control-gear/tridonic-ballasts/tridonic-high-frequency-ballasts-for-t8-tubes-non-dimmable/tridonic-22185216-t8-non-dimmable-ballast-2x18watt
This is 2 x 18w rather than 2 x 15w, but I could get this plus 2 x 18 watt tubes for about £20 - which is a lot cheaper than replacing the whole thing for £70.
Any comments?
--
Cheers,
Roger
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Tubes with heaters would normally be something like 15 ohms between pins. And the same at both ends.
--
*I am a nobody, and nobody is perfect; therefore I am perfect*

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sunday, 24 January 2016 11:43:54 UTC, Roger Mills wrote:

yes

no

no

both tubes are dead

s/tridonic-high-frequency-ballasts-for-t8-tubes-non-dimmable/tridonic-22185 216-t8-non-dimmable-ballast-2x18watt

Probably just dead tubes, but always the unlikely chance a ballast may have killed a tube. I'd fit 2 new tubes, that will probably fix it.
NT
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 24/01/2016 13:46, snipped-for-privacy@gmail.com wrote:

Thanks to everyone who responded. I've now replaced both tubes and all seems to be well again - for the time being, at any rate!
--
Cheers,
Roger
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

They each have a low voltage filament connected across them, so should be quite low resistance. Open circuit means the tube is dead. It also means the ballast isn't very smart - it should shutdown the tubes before it burns out the filaments. Burned out filaments means the ballast carried on trying to run the tubes *after* they were already dead, and that can make the tube ends very hot. It has been known to crack or melt the glass and overheat things near the tube ends (such as the lampholders).

Ballast might well not be dead. I would try with two new tubes.

18W tubes are 2' long, which probably won't fit.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 24/01/2016 14:20, Andrew Gabriel wrote:

Well spotted! I had misread the description of the 18w tubes.
I can't find a 2 x 15w ballast anywhere. Would one designed for 2 x 18w be ok with 15w tubes?
--
Cheers,
Roger
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It's a bit of a cross of technologies. 15W 18" T8 tubes are an old halophosphase tube size, as opposed to modern triphosphor T8 tubes, although any you buy today will be triphosphor. They were the first size of fluorescent tube available in the US, but were never particularly common in the UK. They operate at 300mA which doesn't well match any other tube size, so using a different ballast may not work well.
However, it might not be the ballast.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 24/01/2016 23:16, Andrew Gabriel wrote:

18" was/is common for lighting 2ft fish tanks.
--
mailto: news admac {dot] myzen co uk

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Buy LED tubes and forget the ballast.
--
Adam


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 24/01/2016 14:41, ARW wrote:

Interesting suggestion! Can I get LED tubes which are direct replacements for 'ordinary' tubes - same length and diameter, and pins on the ends which fit the existing holders?
If so, how would these need to the wired? Currently there are 4 pairs of wires which connect to the output end of the ballast. Would each pair of wires have to be directly connected to the incoming mains?
--
Cheers,
Roger
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sunday, 24 January 2016 17:13:07 UTC, Roger Mills wrote:

I looked at the lumens per wat, electronic fluorescent/LED There was not much difference. Price, LED twice the cost. It was in the kitchen so not much used. So I went fluorescent. Things may have changed, LED has come down a lot in price recently.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload


https://www.ledhut.co.uk/led-strip-lights/t8-led-tube-light-600mm-2ft.html
and the link has a wiring diagram on it!
I do not believe that you need any help to work out how to bypass the ballast and wire that circuit.
--
Adam


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 24/01/2016 17:43, ARW wrote:

Fair comment!
Only problem is that nobody seems to make T8 LED tubes less than 2' long, and mine are 18"! Have you seen any as short as this?
--
Cheers,
Roger
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sunday, 24 January 2016 18:03:31 UTC, Roger Mills wrote:

LED tape can be whatever length you want it
NT
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload


Stop complaining and start bragging about extra few inches.
--
Adam


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 17:43 24 Jan 2016, ARW wrote:

Interesting but that lamp is only 900 lumens. Not really as bright as a fluorescent.
--
pamela

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Yes - but it's the latest thing. LED. So must be better. ;-)
--
*I pretend to work. - they pretend to pay me.

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload


Depends on where the light goes. On a traditional flourescent fitting some (maybe 20%) of the light is wasted by lighting up the fitting!
--
Adam


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Depends on the fitting. Not many are matt black. ;-)
--
*I went to school to become a wit, only got halfway through.

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Fit one and do a lux reading at finished floor level before and after.
--
Adam


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.