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03-28-2025, 02:31 PM
Hi Guys
With some of the available toroidal PTs - and maybe some traditional types - it may be necessary to verify the windings and leadouts as the documentation is sometimes minimal.
The first step is to use an ohmmeter to "ring out" the windings. It is handy to use an alligator clip test lead to connect one meter lead to a given winding lead, then both hands are free to probe other leads to see if they connect to the reference wire.
When you find leads that are related, twist them together and flare out the stripped ends so they do not short to each other.
Once you have found all of the related lead sets, make sure none of them are touching each other.
Use a Power Limiting Safety Socket (Mandatory Project in TOT Tonnes of Tone) with the lowest-wattage bulb you can find to power the PT. The primary or primaries of the PT should be specified and if it is a dual wire them in series. This will cut all the secondary voltages in half if you happen to be in North America or Japan. For the rest of the world, high-voltage plate windings will be near their full voltage rating so BE VERY CAREFUL.
With many transformers that have dual secondaries that are identical, the windings also have identical colours. This is fine if you simply wish to parallel them for maximum current, but quite useless for series-connection. You have to ring out the leads to find the related pairs THEN the colours are useful in that it should be easy to connect them for series-aiding (highest voltage from end to end of the series pair).
The above procedure "phases" the windings, where you can see if the voltages add together or cancel out. For example, suppose you have two 6V windings that each have two green wires. You ring them out to see which pairs of wires are for each winding, twisting the related wires together. Initially you simply take a random wire from each pair and link these together. Measure the voltage across the free ends and you will see either 12V or 0V (zero). If it is 12V, mark the free end of the first winding with some tape, or a marker. Mark the connected end of the second winding similarly.
Just to clarify, the phase between windings does not matter unless you need to interconnect them.
With some of the available toroidal PTs - and maybe some traditional types - it may be necessary to verify the windings and leadouts as the documentation is sometimes minimal.
The first step is to use an ohmmeter to "ring out" the windings. It is handy to use an alligator clip test lead to connect one meter lead to a given winding lead, then both hands are free to probe other leads to see if they connect to the reference wire.
When you find leads that are related, twist them together and flare out the stripped ends so they do not short to each other.
Once you have found all of the related lead sets, make sure none of them are touching each other.
Use a Power Limiting Safety Socket (Mandatory Project in TOT Tonnes of Tone) with the lowest-wattage bulb you can find to power the PT. The primary or primaries of the PT should be specified and if it is a dual wire them in series. This will cut all the secondary voltages in half if you happen to be in North America or Japan. For the rest of the world, high-voltage plate windings will be near their full voltage rating so BE VERY CAREFUL.
With many transformers that have dual secondaries that are identical, the windings also have identical colours. This is fine if you simply wish to parallel them for maximum current, but quite useless for series-connection. You have to ring out the leads to find the related pairs THEN the colours are useful in that it should be easy to connect them for series-aiding (highest voltage from end to end of the series pair).
The above procedure "phases" the windings, where you can see if the voltages add together or cancel out. For example, suppose you have two 6V windings that each have two green wires. You ring them out to see which pairs of wires are for each winding, twisting the related wires together. Initially you simply take a random wire from each pair and link these together. Measure the voltage across the free ends and you will see either 12V or 0V (zero). If it is 12V, mark the free end of the first winding with some tape, or a marker. Mark the connected end of the second winding similarly.
Just to clarify, the phase between windings does not matter unless you need to interconnect them.
