[sdiy] (no subject)

[Rutger Vlek]

Hi List,

I'm considering the modification of a 115V US Yamaha A-3 organ to make it
compatible with both 115 and 230V (I live in the EU). The power supply runs
from a transformer with 2 secondaries, providing 6.3V AC and 13V AC to the
PSU. The PSU is relatively simple (60s technology, no voltage regulators,
just caps, resistors and a full wave recto). It generates DC at +6V and
+12V (roughly, it accuracy isn't extremely important in this instrument).

I have sourced a Hammond transformer with 12.6V AC out and a centre tap. Is
there any harm in using the centre tap for the 6.3V and the end taps for
the 12.6V supply to the PSU? It means the coil between one end and centre
tap gets a little more loading than the other side. The same probably
happens with a split supply +/- voltages and a centre tapped transformer,
am I correct?

The other question is: the PSU circuit that generates +12VDC from the 13VAC
transformer output uses a choke shortly after the full wave recto. Is there
any interaction to be expected between power transformer and choke that
could make my replacement transformer not work in this situation? Is it
tuned to impedance properties of the power transformer?

Regards,

Rutger
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20170306/3d6740f3/attachment.htm>