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Uncle Bulgaria · 5th Feb 2019, 3:53 am

Thank you Lawrence, that's very helpful.

I thought there would be a relationship between the resistance ratio and the turns. I got wildly varying and worrying voltages on the secondary when putting low VAC across the primary, so reversed it. with 2 - 12VAC on the secondary, the average ratio was 1:13, when I could get a reading on the AVOmeter. (sub 1V).

If that is correct, then Rt is about 553R, with n = 6.5.

However, that's still far too high as Vaa' will be about 3kV at 240V! Surely the ratio is absolute, regardless of there being no load? It remained constant over the applied voltage range, which has confused me. I checked I am measuring the right secondaries, that go to the right pins of the EZ80 socket.

Where did you get the 480V from in the manual, and why am I not getting a reasonably measured value? I am overlooking it in the Ferrograph manual I have, if that is the one you are referring to.

5th Feb 2019, 3:53 am	#25
Uncle Bulgaria Nonode Join Date: May 2016 Location: Cornwall, UK. Posts: 2,335	Re: Ferrograph 4A: Restoration advice needed Thank you Lawrence, that's very helpful. I thought there would be a relationship between the resistance ratio and the turns. I got wildly varying and worrying voltages on the secondary when putting low VAC across the primary, so reversed it. with 2 - 12VAC on the secondary, the average ratio was 1:13, when I could get a reading on the AVOmeter. (sub 1V). If that is correct, then Rt is about 553R, with n = 6.5. However, that's still far too high as Vaa' will be about 3kV at 240V! Surely the ratio is absolute, regardless of there being no load? It remained constant over the applied voltage range, which has confused me. I checked I am measuring the right secondaries, that go to the right pins of the EZ80 socket. Where did you get the 480V from in the manual, and why am I not getting a reasonably measured value? I am overlooking it in the Ferrograph manual I have, if that is the one you are referring to.