AVR-Chat

On the AC side
Connect the High, hot, black wire to one wire of the transformer 
input.
Connect the Low, neutral, white wire to the other wire of the 
transformer input.
Connect the Ground, green wire to the metal cabinet. Mount the 
transformer to the metal cabinet. It would be best to use the same 
screw to mount the transformer and tie the Ground wire also. I would 
not connect the 120 VAC Ground to the Common of your DC power supply.
That takes care of the 120 VAC side.

The low voltage AC side:
Connect the output of the transformer through your bridge, or 
whatever, rectifier, filters and regulators. Now you should have a 
nice clean DC power source for your equipment completely isolated 
from the input side of the transformer. I would NOT connect the DC 
Common to the input AC Ground. Lots of times people talk about DC 
Ground when in fact it does not connect to Ground at all. It is 
Common, DC Common, to many places in the circuit but is never 
connected to Ground. These two electrical places exsist but neighter 
knows about the other except through the magnetic coupling of the 
transformer. Keep it that way.

Mike

--- In AVR-Chat@yahoogroups.com, "Randy & Zonya Ledyard" 
<rledyard@b...> wrote:
> Basic question about grounding here, couldn't find the answer on 
several
> schematics I looked at, so I thought I'd ask it here, so the 
experts can set
> me straight.
> 
> I putting together a power supply for my son, to power several of 
his guitar
> effects boxes, and I had a question about grounding.
> 
> This is a basic transformer/diode bridge/7809 regulator with filter 
caps
> circuit, running off 120 VAC (US)
> 
> Do I connect the ground from the 110 VAC to the ground on the DC 
side? If
> it's in a metal case, should the case be grounded to the 110 VAC 
side also?