PA060 No Load secondary HV tolerances

Hello,

Does anyone know the acceptable tolerance for the high voltage secondary portion of the PA060 type power transformer in no-load condition?

I see specs show 360 55 0 360 but mine is measuring 345 65 0 355 with the specified primary voltage.

How critical are these voltages in the ST-70 and if so what should I watch out for?

All the low voltages are spot on.

Any suggestion/schematic for a load condition test that would somewhat replicate loads in the ST-70?


Thanks!

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Hi Peter,

AC Mains is stable @231V. The power transformer is a 230 volt model from a supplier here in Europe.

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Thanks, Peter

Yes, that was the plan.

Maybe someone has a PA060 laying around or still unbuilt that could post their no-load readings but will proceed with the build and see how it goes.

From one of Bob Latino's posts about testing iron:

1. For the power transformer ... Connect the two BLACK wires to a 120 volt AC power source ..
Measure the AC voltage across the two RED wires > 700 - 760 VAC
Measure the AC volatge across the two GREEN wires > 6 - 7.5 volts AC
Measure the AC voltage across the two BROWN wires > 6 - 7.5 volts AC
Measure the AC voltage from the RED/BLACK wire to the RED/YELLOW wire > 55 to 60 volts AC
Measure the AC voltage from the BROWN/YELLOW to the RED/YELLOW - 3 to 4 volts AC
Measure the AC voltage from the GREEN/YELLOW to the RED/YELLOW - 3 to 4 volts AC

So guess pretty close, a bit high on the 50-60V but that should drop when there's a load.

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Peter,

Here's the source thread. Looks like unloaded to me.

https://dynacotubeaudio.forumotion.com/t2111-testing-st-70-iron?highlight=transformer