testing low voltage transformers
- Thread starter dimmer
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Just plug it in and see if it works. Some wil only provide a voltage if there is a load attached.
Why do you ask these questions, grasshopper?
Just plug it in and see if it works. Some wil only provide a voltage if there is a load attached.
Why do you ask these questions, grasshopper?
Well sometimes you change the bulb and it does not work, then you change the transformer and it still does not work, so you change the lamp holder.....
I just changed a transformer still not working, (Aurora) changed again and it worked.
Would a blown transformer test a certain way?
I just changed a transformer still not working, (Aurora) changed again and it worked.
Would a blown transformer test a certain way?
But that is not
That is a transformer installed.
If its installed. Check 230v on the input. If it is there then............
Put a known working lamp across the output terminals.
If the lamp comes on then its the lamp holder
If the lamp doesnt come on its the tranny.
Most of the ELV transformers to suit 12v halogen lights are just a load of electronics so you can't put an ohm meter on the input to test the windings.
That is a transformer installed.
If its installed. Check 230v on the input. If it is there then............
Put a known working lamp across the output terminals.
If the lamp comes on then its the lamp holder
If the lamp doesnt come on its the tranny.
Most of the ELV transformers to suit 12v halogen lights are just a load of electronics so you can't put an ohm meter on the input to test the windings.
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As Taylortwocities says the device used in the main to run extra low voltage lights is an inverter not a transformer.
What it does is change the input to DC and charge a capacitor then turn it back to AC at a much higher frequency with the ability to change the mark / space ratio.
The output high frequency AC is monitored and the mark / space ratio changed to ensure spot on RMS voltage.
However there is often a limit to how much it can change the mark / space ratio so it also has a cut out should the load drop below a pre-set level.
As a result they would only work with a load so only real way to test is to build a test rig which will have the load. i.e. make it work a lamp.
The old transformers could be tested of sorts by measuring input and output ohms but unless you had a set of figures to compare the readings with even with these only real test was to power it up.
However it is much easier to measure the lamp resistance. Even this is not quite what one would expect as the filament resistance changes as it warms up, and also since the filament is often a coil it will work slightly different with AC to DC. But you get a reasonable reading enough to know if it will likely work or not.
What it does is change the input to DC and charge a capacitor then turn it back to AC at a much higher frequency with the ability to change the mark / space ratio.
The output high frequency AC is monitored and the mark / space ratio changed to ensure spot on RMS voltage.
However there is often a limit to how much it can change the mark / space ratio so it also has a cut out should the load drop below a pre-set level.
As a result they would only work with a load so only real way to test is to build a test rig which will have the load. i.e. make it work a lamp.
The old transformers could be tested of sorts by measuring input and output ohms but unless you had a set of figures to compare the readings with even with these only real test was to power it up.
However it is much easier to measure the lamp resistance. Even this is not quite what one would expect as the filament resistance changes as it warms up, and also since the filament is often a coil it will work slightly different with AC to DC. But you get a reasonable reading enough to know if it will likely work or not.
The 'transformer is difficult or impossible to test in isolation, but it's relatively easy to check the input (230V present) and the load at the output (DC resistance of lamps)
230V present + DC resistance across output consistent with maximum and minimum load specification = faulty 'transformer'
Now write out 100 times 'I must read all replies before posting'
230V present + DC resistance across output consistent with maximum and minimum load specification = faulty 'transformer'
Now write out 100 times 'I must read all replies before posting'
Same as everyone else it saying. Check for 230V across the supply. If thats good, check a 12V lamp directly onto the output terminals. If it lights up the tranny is ok. If it doesn't, swap it out.
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