What is the normal operating frequency of that transformer? 1000 Hz test
frequency seems to be on the rather low side. What is the frequency of the
ringing that you're seeing? That's probably the resonant frequency of the
x-former with it's associated circuitry attached and I would expect to see
the X-former normally being operated at about the same frequency. I'm not
familiar with the t935 but IMO you'd probably be better off using a very
low voltage AC signal instead of a square wave to drive the transformer
when testing. Coupling the x-fomer to the signal source through a capacitor
should remove most the higher frequency harmonics from the square wave and
leave you with mostly the base frequency sine wave.
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On Sun, May 9, 2021 at 11:03 AM Ham Radio <bernard.murphy@...> wrote:
The ring test with a 10 volt 1000 Hz square wave with a duty cycle of 1%
shows ringing on the primary winding of T460 - so that looks good!
No ringing though, on the feedback winding on pins 3 and 6 with the same
setup as above. Not sure ? if the ring test would work here as they may
be only a few turns on the feedback winding. That winding measures a dead
short on the AVO /100 resistance scale but that does not mean the winding
is shorted.
I assume that Q444 generates the frequency of the switching pulses for
Q458 through the feedback winding.
Not too sure what to try next ...
--
Regards,
Bernie Murphy
