12v light transformer problem in cooker hood

[darkmagi]

As the title states i have a problem with the lights in my baumatic cooker hood, both the lights stopped working last sat night as i was cooking a curry, Not too bothered as it did not affect the tast of the curry but my wife wants them fixed, Both the bulbs seem ok but when i checked the bulb holder it is only putting out 7v, Im assuming that its supposed to put out 12v but i wanted to make sure before i go and buy another transformer for the hood.

 

[ericmark]

Many transformers are not simple transformers but switch mode power supplies. These have a minimum and maximum output and often have some form of shut down when the minimum demand has not been met.

Voltage readings need to be taken under load as a result so really assuming bulb is OK if voltage is 7v then the bulb holder must be at fault or the lamp would be working but dim.

If 7v is measured without the bulb being in the holder then it means nothing.

 

[Steve]

Does your hood have halogen lights? If so, use this as an opportunity to replace these hideous things with something better - fluorescent or LED.

 

[RF Lighting]

And how would you do that then, when it is all built in to the cooker hood?

 

[Steve]

And how would you do that then, when it is all built in to the cooker hood?

A couple of modifications. I could sort something if I had a photo of the appliance's gubbins.

Even changing the lampholders for GU10s and using LED lamps - this could be an easy one.

 

[RF Lighting]

They are usually just 2no. G4 halogen capsules. No room to fit one of those useless LEDs in it's place.

I see you've jumped on the "I hate halogen" bandwagon. Why?

 

[darkmagi]

Many transformers are not simple transformers but switch mode power supplies. These have a minimum and maximum output and often have some form of shut down when the minimum demand has not been met.

Voltage readings need to be taken under load as a result so really assuming bulb is OK if voltage is 7v then the bulb holder must be at fault or the lamp would be working but dim.

If 7v is measured without the bulb being in the holder then it means nothing.

Finally i managed to have a look under the extractor fan and from what i can see inside the extractor housing the main wire goes into a box which i assume holds the wiring for the different switches on the front of the extractor, the main power switch the 3 fan switches and the light switch, a wires comes from this box that goes up to the fan and another wire comes down into the transformer, a wire comes out of the transformer and goes to a 3 way multi connector for the lights.

When i take a reading from the transformer input i get a constant reading of 248v when i switch the lights on i get a reading of 17v at the 12v end of the transformer but the lights still do not work.

anyone have any ideas or is it as simple as the transformer is needing replaced.

 

[darkmagi]

finally changed the transformer for a new one & it works perfectly so i can only assume the transformer was damaged even though it was putting out 17v.

 

[Taylortwocities]

Glad it working. Thought it was only 7volts, not 17volts But hey

Per the above its tricky to measure the output of some of those trannies. It is certainly not a DC output so it will give false readings if you set the multimeter to DC. It may not give an output on no load.
The best test (I have found) is to just strap a known working lamp to the output. Make sure there is mains going in, if the lamp doesn't work just change the tranny!

 

[darkmagi]

i was getting a reading of 7v when i checked the bulb holder without the bulb in, but when i had the bulb in & switched on i was getting a reading of 17v but what the hey its working now & thats the main thing...