More power supply issues

[llamma]

O.K.. here goes.

Still working on the power supply thing for my bass preamp,

I got myself some 7812 and 7912 regulators and have found a 6.3-0-6.3 transformer,

using the option of connecting the two outside windings to give me 12.6v and then halfwave rectifing them to give me a + and - voltage, then passing thru each of the regulators,

followed the schematics from geo and esp,

the problem,    i'm getting about 18v - 19v at the outputs,   why is this so high, i though these were meant to only put out 12v?

please help, have i got the wrong pinouts or something,

cheers
Blair

[Joep]

Hi,

When you rectify the AC voltage from the transformer, the DC voltage will be 1,4 times higher. If you use half wave rectification, it will be less, 1,2 to 1,3.

Also you don't put any "load" on the transformer, so the AC voltage will higher than the 12,6. Often the AC output voltage is specified for full load.

If you have 18-19v AFTER the 7x12's something must be wrong, it looks like they are shorted. 7812 and 7912 have different pinouts, be sure to double check them....

Bye,

Joep

[llamma]

Ooops,

now i feel dumb,

just after posting this i reverse traced my layout, and discovered i had forgotten to put the links in from the gnd traces to the gnds on the 7x12's

i hate when that happens,

it's putting out the correct 12v now

cheers
Blair