Power supply confusion

[ShieldJaguar]

Hi all,

Have partly built a GC, loosely based on BrianGTs.
The following are wired up:

Trafo 160vac 18v x18v
2x bridges made from MUR860

Starting to build the Chip boards 2x Panasonic Caps et al, but am worried that i've made a mistake. The Zero volt rail-does it come from the trafo?, the bridges?
In some of the simplified drawings i've seen you take a pair of secondaries join them together through a pair of Caps, then the link from these gives you your Zero volt rail is this right? So i need 8 caps in total? including the 2 Panasonics next to each Chip?
Sorry if this seems dumb-hope someone can be gentle with me and explain(in simple terms)

Thanks
SJ

[Fenris]

Since you have a dual secondary transformer, the zero volt "rail" comes from connecting the positive of one of the bridges to the negative of the other. Since the transformer secondaries are electrically isolated from each other, the voltages are just relative. The joined rail will see one of the other rails as more positive and the other as more negative, giving you your +/ground/- rails.

If you had a transformer with a center tap, you would use the center tap as the ground reference point and a single bridge to get the +/- rails.

You should always put a cap between the + rail and ground and the - rail and ground in order to smooth/filter the input voltage surges into cleaner DC.

[officeboy]

Since you are using dual bridges, and have dual secondaries. Then you just take each secondary and connect it to each bridge, and that will give you + and -, then you just join one plus and one minus, and that will be your "ground"

IF you didn't have dual secondaries (only center tapped) and you wanted to use just a single bridge you would run the outermost lines to the single bridge, and the center tap (or joined secondaries) would be your "ground"

The picture might help explain it.

[officeboy]

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*this is only a test*

[ShieldJaguar]

Thanks ppl i'm sorted now

SJ