Halogen transformer not working

I have 220 volt AC to 12 Volt electronic transformer. It doesn't give any out put 12 Volt AC. Both 12 v output phase and neutral wires are getting phase supply.
May I know what is the problem?

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It's broken?
It doesn't have a load?

No. see the new pics . load not connected.

Hi,
Do you have a DMM?
If so, with the power supply UNPLUGGED from the power.
Measure the resistance between the two 12Vac wires.

Have you checked the solder joints for cracked or dry joints?
Can you post a clearer image of the underside of the PCB, particularly at the end with the transistors soldered in.

Thanks.. Tom... :smiley: :+1: :coffee: :australia:

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That's not just a transformer. There are additional components. This is a transformer.

Are there any other external connections (like maybe for a switch or something)?

Does the transformer body vibrate or get warm? Is there any indication of power? (Don't touch the incoming AC power. :wink: ) They don't always vibrate, but they usually warm-up when power is applied.

I see a rating of 20W. What are you trying to power with it?

Hi,
Its a very elementary switch mode power supply.
Something like this, the four diodes are the bridge in the diagram.
This is only an example of a simple LED power supply.
Transformer my be different.
smpssimple

Tom... :smiley: :+1: :coffee: :australia:

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Looks like a dry joint/ bad repair to the transistor collector.
Could also be a blown fuse.
Without further information, who knows.
G

New pic posted.

Resistance between 12 v wires 7 ohms

I trust you realise that the "AC" output is nothing like 50 or 60 Hz, but is a much higher frequency which your meter may not correctly handle. :astonished:

I see signs of resoldering pretty much all over the pcb.

Is it worth salvaging this? What does a 20W 12V SMPS cost these days, the whole of €7,50 or so?

I want to repair.

Ok, that's fine, then start by tracing out the schematic and determining component types. From there, it's a matter of diagnosing the fault. You will need a digital multimeter and preferably an oscilloscope. I assume you have experience working with lethal voltages and know how to work on a circuit like this safely. If not, please step away from this and buy a new device.

I updated new picture and resistance 7 ohm.

Hi,
This should help, the part numbers of the BJTs should tell you if they are PNP or NPN.

Tom... :smiley: :+1: :coffee: :australia:

1.Transformer No.200807011
2.Green capacitotors 2F333
3. Four diodes IN400KE
4. Yellow capacitor 104
5. Two Diodes IN4007
6.Transistor No. 13002B PNP

Part numbers are
1.Transformer No.200807011
2.Green capacitotors 2F333
3. Four diodes IN400KE
4. Yellow capacitor 104
5. Two Diodes IN4007
6.Transistor No. 13002B PNP

Hi,
This may help.
You can add the values.

T designates a transformer pin.

Tom.. :smiley: :+1: :coffee: :australia:

Thank you I will check.

Looks plausible; did you trace it from the PCB photos?

@sunil125 the schematic that @TomGeorge posted should help you troubleshoot. I'd start by measuring the different components for continuity and lack of shorts without power to the device. You can check all diodes and the two transistors this way, as well as the transformer. There's a good chance this already gives some insight.
If I were to place any bets I'd say that one of the transistors has made it to heaven, but it may have taken one or two diodes and/or a capacitor along with it (or vice versa).