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Phil Allison[_2_]

I looked over what I had previously written and perhaps I didn’t explain
this properly. I have a 24VCT transformer. The transformer needs to power
24VAC equipment as well as 12VDC equipment. For the DC circuit I first tried
using a bridge directly off the 24V winding. As soon as I connected up the
filter cap the DC output went to 35V, which is probably too high to feed my
12V regulator.

Several people came up with some great ideas to address this, and I then
realized that I had a center tap that was not being used. So I connected my
bridge across the center tap and one side of the secondary. This time the
13VAC when FW rectified using the bridge went to about 19VDC, which is a
safe input to the regulator. Although this worked, I wasn’t happy about
unbalancing the transformer this way so I posted my results.

Unless I seriously misunderstood It was suggested here that I come off the
full secondary output with two diodes, cathodes tied together, (typical FW
rectifier), and use the center tap as my negative return. I didn't think
that would make any difference in the output voltage from using a bridge
without the center tap however I tried it anyway. As I suspected it would,
the DC output again went to 35V when I connected the filter up.

** Center tap transformers are ALWAYS double the AC voltage of bridge
rectifier ones for the same final DC voltage.

You have made a dopey wiring error.

..... Phil