Identification of an AC transformer

It's an AC/AC transformer, the rectifier was probably on the red/black lines. Usually Yellow\Green lines are for AC mains (according to international standards, but it also depends on the age of the device).

Your best bet is to hook up a signal generator, and see what the step down ratio is if you want to use it.

The other thing that will be of use is any markings on the outside of the clock that specify the current and voltage (you need the current) because that will give you a good idea of the saturation point of the transformer and how much power can be run through it.


I didn't see the blue black line in the picture which is not clearly indicated: The primary is most likely blue brown and there are two secondaries, in this case red/black are one secondary and the other secondary is yellow/green

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It's a transformer. It outputs lower-voltage AC on the secondary wires.

As you surmised, the red/yellow/green/black are secondary windings and the blue/brown are primary going to the mains voltage. You have that figured out so far. Now the next step is to figure out how the secondary windings are connected and what their outputs are to see if they're useful (they very probably are.)

The 'safe' way: Use an ohmmeter to determine which coils connect to which, and how they relate to each other. Determine this by seeing the relative series resistance between each wire. You may find that there are two separate coils, or that they're a single coil with multiple taps. More about this in a bit.

The 'fun' way: test it. Connect AC up to the primary and use the voltmeter to measure the secondary AC voltages, wire-to-wire, to figure this out. Do this with care obviously, though the secondaries are low enough voltage that you're not at significant risk for shock.

"More about this". If this unit came from a VF (vacuum fluorescent) type clock, my guess is that it has two separate windings: one for 3VAC for VF tube filament, and the other 7~9VAC for logic power which would have fed to a full-wave bridge on the board (maybe you can check this if you still have the board.)

If I had to wager further, the logic power pair would be the black and red pair.

You probably won't find a datasheet as the transformer itself quite likely is not a consumer part but a Philips internal design, tailered to this specific product (alarm clock FM/AM radio) and to mass production.

I wouldn't bother investigating it, but just buy a transformer that fits your need, made by a reliable manufacturer with a well defined datasheet. They're not that expensive...