[Russtafarian]

I'm putting together a power supply for a LM4870 chip amp.  I'm using the BG Micro transformer that's spec'd into the Felicia project.  Using it as-is without removing any jumpers I get 30VAC on the secondary (7 & 12) when I put 120VAC on the primary (1 & 6).  After rectification and filtering I'm getting +/- 22VDC.  I though the post rectification voltage was supposed to go up, not down.  Why is this happening?  Is my connection from the transformer to the bridge rectifier mixed up?

[JoeE SP9]

A rectifier being nothing more than 4 diodes tied together (full bridge) will always have a voltage drop because a diode itself has a voltage drop.

[Occam]

.....Using it as-is without removing any jumpers I get 30VAC on the secondary (7 & 12) when I put 120VAC on the primary (1 & 6).  After rectification and filtering I'm getting +/- 22VDC.  I though the post rectification voltage was supposed to go up, not down.  Why is this happening?  Is my connection from the transformer to the bridge rectifier mixed up?

No, you are getting a higher voltage.... 22vdc - (-22vdc) = 44vdc
So you've grounded the secondaries 'center tap' and hook up a bridge with caps, etc and gotten 30 x 1.414 = 42vdc, which isn't exactly 44vdc and no diode voltage drops, so I assume your measurements are a bit squirley, but somewhat reasonable.

[Russtafarian]

Mystery resolved!  Thanks Paul.