help with transformer

Hi can anyone please help me to try and get this transformer working. I don't no which rail is which many thanks.


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2006-08-15 9:46 pm
With an ohm-meter you test all pairs of pins. Those that have "less than infinite" resistance are windings (it's going to be quite low, primaries will have several tens (even hundreds?) of ohms, secondaries just few ohms - but you don't really need the exact value).

It may have a primary that accomodates several voltages, like 110, 220, 240. In that case you'd have three "growing" resistances (longer lengths of cable) over four pins (first and second, third, fourth).
Hmm, those primaries may be disconnected, if the voltage setting is made externally, like somewhere on the PCB or even in the back panel.

Once the windings are determined, what I usually do is to put a low AC voltage (like 10V; or 22V is easy for calculation, here in Europe) into what could be the primary, and I measure the voltage on the other windings. This lets you determine the turns ratios.
The primary has a thin wire, compared to high-current secondaries (but the secondaries may also all be low-current and have thin wire).
But if you do this measure with 5V AC, there's no risk even putting it into a secondary.

For VA-rating there's an estimation based on weight. If I remember well it's something like 40VA per Kg. Careful, this is total VA, the sum of all secondaries.
And the thickness of each cable lets you estimate how much each winding could bear.

Just use it at half of your VA estimates, to stay on the safe side.

Hope this helps.

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