Now it works, now it doesn't

[monday]

I have 3 x MR16 12v downlights installed in a pelmet over a worktop/chests of drawers in a bedroom. They are wired to a 2 gang dimmer switch; the other dimmer works the central ceiling light. They were professionally installed >10 years ago as part of a bedroom refit. They have worked perfectly until the other day when they refused to come on. It seemed unlikely that all three lamps would fail simultaneously but I realised they are probably all wired via a single PSU which had presumably packed up. I made plans to fix this after a weekend so that I could get a new PSU.

Trying again today, it all worked perfectly. I'm not going gaga, my wife tried it as well. What's going on? I think I have read that these PSU's have a thermal cut out? Did that trip and has taken time to reset? What would cause it to trip in the first place? Is it likely to do it again more permanently so I should change it anyway? Or should I follow the old principle of "If it ain't broke.....?

 

[flameport]

I think I have read that these PSU's have a thermal cut out? Did that trip and has taken time to reset?

Very likely, it will disconnect the supply when it's hot. Cooling will take a while, some might need to be switched off for an extended time before they will work again.

Is it likely to do it again more permanently so I should change it anyway?

Also very likely. Things do not repair themselves.
Change the lights to LED ones. Those halogen lamps and the transformer affairs for them have been obsolete for several years.

 

[robinbanks]

Either a thermal cut, or some circuit failure that shows up when warm due to thermal expansion or breakdown of a component as it heats up?

If you do replace them, and you made good use of the dimmer when running on halogens, do some tests / try before you buy if you can, with dimmable LEDS. Most dimmable LED just get less bright when you dim them but halogens naturally become redder (warmer colour temperature) as they dim. If the halogens created a particular ambiance in your bedroom, you may find the light from most dimmable LEDs far less remarkable/suitable for what you've become accustomed to

 

[Murdochcat]

Faulty dimmer?

 

[monday]

Many thanks for responses. The consensus seems to be that, as I suspected, the PSU has cut out and taken time to reset. The lamps in question are my last remaining MR16 halogens, simply because they have never given any trouble. I note I can get MR16 LEDs so three new lamps and a suitable driver seem to be in order.

Murdochat - I take your point about the dimmer but I feel that it would fail and not recover. I may be wrong......