• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

How to check output trans ?

Hi all !

How to check an output transformer, I have ohmmeter Fluke of course, and also scope, frequency generator, ect ...

1.5k/84-8-16 ohms gapped for 250ma
For PSE 300B.

I want to be sure all wiring is on the right way, no wiring in opposite phase by example, ect..

Thanks in advance.

Gilles.:)
 
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The easiest way is to inject a low voltage at the secondary of the DUT (Device Under Test) from a low voltage alternate source, like a heater secondary (5 or 6.3VAC), then measure secondary (primary) voltage and phase, using both channels of the oscillo simultaneously. If the DUT becomes too hot, and low voltage appears at the primary, then it is shortcircuited or not suitable for those frequency (50/60Hz). Also, the voltage ratio will give you the turns ratio, and, squared, will give you the impedance ratio.
 
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The easiest way is to inject a low voltage at the secondary of the DUT (Device Under Test) from a low voltage alternate source, like a heater secondary (5 or 6.3VAC), then measure secondary (primary) voltage and phase, using both channels of the oscillo simultaneously. If the DUT becomes too hot, and low voltage appears at the primary, then it is shortcircuited or not suitable for those frequency (50/60Hz). Also, the voltage ratio will give you the turns ratio, and, squared, will give you the impedance ratio.

It is much safer to inject the signal into a primary winding - 5V into the OT secondary can easily produce lethal voltages on the primary and necessitate using 100x oscilloscope probes to protect the 'scope.

Inject 5V into a primary winding and measure with an DMM, no high voltages. Dont connect/disconnect with the power source powered up.

And if you are not sure which winding is which, measure DC resistance and pick the largest resistance winding as the test primary winding.
 
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