To be honest I think that's the more reasonable explanation. When I read through Steve's post, that is what I was thinking may have been the cause.

_________________

I'm not a great fan of electronic gear in terms of reliability and the carbon cost of making a PCB and electronic components compared with a steel can, a lump of iron and some copper wire.

2 further reminders of this have come to light   in the last week.

Holophane QSMs fitted with Harvard electronic gear are notoriously unreliable. The ballast clearly states that if the ambient temperature of operation is greater than 30C it must be mounted label side up - i.e. largest flattest side up to dissipate heat. The power transistors are mounted along the long thin sides of the box, so label up ensures these sides are vertical to maximise heat dissipation.

On the QSM with a 150W lamp a few inches away in an aluminium reflector optic - which will transfer heat into the lantern interior - the ballast is mounted with the label to the side - so whilst one set of transistors faces up, the other set is face down and can't get rid of the heat. To make matters worse, despite the ballast being mounted on a great big lump of steel angle - it is mounted with a self adhesive pad which covers the entire base of the ballast insulating it from the mounting bracket.

So the whole thing is mounted so that it can't dissipate heat with a 150W heater in the same box. No wonder they fail.

Example 2 - Philips 180W SOX ignitor from Nick217 which no longer works. When dismantled, it is clear the power transistor has gone pop. This is a 1500V device yet it is clear it has suffered over voltage from the high voltage spike when the lamp strikes. So a poor spec device - a 2000V device is probably needed or an over voltage crowbar protection circuit or VDR should have been designed into the circuit to protect the transistor. The ignitor is also far more complex than a SOX ignitor for lower wattage lamps - far more components and also included is an oscillator circuit which isn't needed for smaller wattages.

On top of that, a series high voltage capacitor is still required, so that element of potential unreliability isn't eliminated by moving from Leak to ignitor gear. So it may be cheaper to make and possibly cheaper to run, but in reality less reliable than the old style gear. Arrgh..

So in theory the heat emmitted from the lamp is basically cooking the electronic ballast. .

_________________
From streetlighting to radio, dance through the night whilst the streetlights are glowing outside.

So can the ignitor be fixed?
As it does seem to be a common fault explains why MA60/SRS201s don't get used much anymore.

It sounds like somebody has now seen inside/has a QSM. All of mine are now tucked into storage, but I can say it is the same setup in these, and the 70w versions fail regularly too. Some have had different ballasts fitted and are redeployed back into service, so I'd presume those can work on their sides. And because the Harvard one has been ripped off the base plate, the replacement ones are screwed on to the plate rather than stuck on. I believe there are different mounting plates that vary according to the spec required (under the plate is a specific cat. number and description) - and a QSM is symmetrical inside and so could have two ballasts in there, or a 250w magnetic ballast and the ignitor on the other side.
In this sense, the QSS is a better design, because the ballast is seperated by a bulkhead between it and the optic - and there is also a bulkhead in the same place in the canopy, so that when the canopy is closed the ballast is effectively in its own room. There are also cooling fins under the ballast section of the lantern.

_________________

If I can source a replacement part, then yes.

You once showed me the inside of your QSM Chris, so I had a rough idea on how close the EB is to the lamp.

_________________
From streetlighting to radio, dance through the night whilst the streetlights are glowing outside.

Okay thank you.

On another note, I now use my 55W Residum to light my bedroom. Just been playing about with the three different types of 55W PL-L bulbs with it and found, the normal Crompton bulbs take around 5 mins to warm up, but the Philips Master and Master Outdoor take around 1 min to warm up, strange?

Although the ballast is not designed to be run in harsh environments as it is suitable to be run on Emergency Lighting Circuits!
If they do design a outdoor ballast suitable for -20 - 40 degrees Celsius, then maybe problem solved?

Perhaps its time to leave electronic ballasts to fluorescent & Cosmo as they seem to be much more reliable then SON and SOX.

Thoughts?

Lamp run up time will be due to the gas fill and the phosphor coating used. I suspect the Philips lamps are designed to work at lower temperatures and hence run up quicker inside where as the Crompton one probably uses a less energetic phosphor and electrodes giving a longer run up.

Fluorescent lamps don't need a significantly high voltage to strike them, SOX needs higher and SON higher still. SON runs at the highest current of all 3. All of this means you need higher quality components/better design as the ballast is more stressed than a fluorescent one. Cut corners and lifetimes suffer.

Until recently Cosmo gear was only available from Philips. Now they have allowed license production I wonder if quality and reliability will fall?

Potentially, yes. There will be some that remain fairly reliable, such as Philips ballasts, and Zodion also seem to make pretty healthy kit. I still think electronic ballasts should be left for CFL, LED and Cosmo.

_________________