Scott Scoville
- Sep 12, 2016
- 2
- Joined
- Sep 12, 2016
- Messages
- 2
I found this forum through googling up this old post from Arfa Daily, 2005, and hope getting help understanding it:
"I had an old Post Office local system ring generator that did the job very
simply. It had a transformer with a split winding on one side, and a single
winding on the other. The split windings were linked in series by a 2uF
paper capacitor, and a single diode ( IN4007 style ) was in series with one
of the outside terminals. The diode half wave rectified the mains going in,
providing the transformer with half mains frequency pulses ( 25Hz in the
UK ). The cap between the windings provided rough tuning, which took the
waveform back to something approximating a sine wave. Out of the other side
of the transformer came a reasonable sine wave at about 80v p-p.
"I guess that the same thing could be reproduced now using a split primary
power transformer, with a secondary of say 40 - 0 - 40. The value of the cap
could be played with a bit for best waveshaping to suit the tranny. I doubt
that you would notice the frequency being 30Hz US or 25Hz UK"
Arfa
I would love to see a circuit sketch. I don't understand the significance of the split winding, and I do not quite see how lopping half the main signal will halve the frequency, without reversing polarity somehow.
Thanks
"I had an old Post Office local system ring generator that did the job very
simply. It had a transformer with a split winding on one side, and a single
winding on the other. The split windings were linked in series by a 2uF
paper capacitor, and a single diode ( IN4007 style ) was in series with one
of the outside terminals. The diode half wave rectified the mains going in,
providing the transformer with half mains frequency pulses ( 25Hz in the
UK ). The cap between the windings provided rough tuning, which took the
waveform back to something approximating a sine wave. Out of the other side
of the transformer came a reasonable sine wave at about 80v p-p.
"I guess that the same thing could be reproduced now using a split primary
power transformer, with a secondary of say 40 - 0 - 40. The value of the cap
could be played with a bit for best waveshaping to suit the tranny. I doubt
that you would notice the frequency being 30Hz US or 25Hz UK"
Arfa
I would love to see a circuit sketch. I don't understand the significance of the split winding, and I do not quite see how lopping half the main signal will halve the frequency, without reversing polarity somehow.
Thanks
