28 Nov
2010
28 Nov
'10
3:11 p.m.
Now that I have access to the main unit the plot thickens. All of the
outputs of the potted brick go to full-wave bridge rectifiers in the main
unit such that you get a plus and minus voltage reference to the CT ( center
tap ). That big potted POS is nothing more than a big friggin transformer !
Right... That should make things a little simpler. But why so many
secondary windings?
The main output leads ( 1 2 and 3 ) have 28 VAC coming
out of them. I put a
Variac on the " transformer " and turned it up very slowly. At not much
voltage it gets very HOT ( I suspect shorted windings or a whole shorted
primary on the input side. The 28 VAC output figure came from estimating
Unforutnatel, if you have shorted turns in a winding, it will throw the
voltages off.
I asusme you can now identify the ends and taps of the windings, based on
the rectifiers, etc, in the main unit. Can you make sensible estimates of
the secondary votlages from that (e.g. if thres's a smoothing capacitor
rated at 25V, the RMS ac input can't be more than 25/sqrt(2)). If there
are 3 terminal regualtors, or simular, you can prsumably deduce a
sensible input voltage for them.
-tony