Bipolar power supply issues

[w!ll]

Hi, just wondering if anyone can help me with some issues i'm having with the GGG bipolar power supply found here http://www.generalguitargadgets.com/pdf/ggg_bipolar_ps.pdf. I've had this working previously, but it's acting strangely, and to the best of my recollection i haven't changed anything. The problem I've got is that 7915 regulator is at about -20v when the power supply isn't connected to anything, it should be around -15v. The positive Regulator is fine when there is no circuit connected. Input voltage on the 7915 is -28v, input on the 7815 is 28v. Both grounds are fine. I think the wiring is fine and i checked all the solder joints. This is also the 3rd regulator i've tried, all the same problem.

However, connect the power supply to a common circuit (in this case a frequency analyzer) and the postive voltage drops to zero, and the negative to about -15v. I don't really understand, is this a current issue? How can i measure the current from a bipolar powersupply? Can anyone help? it would be greatly appreciated!

Will

[Nasse]

"Both grounds are fine"

What do you mean, there is only one ground in that circuit

You can measure current separately on + and - sides, you need two multimeters or do first another and then another


I´m not sure but some regulators might need a small load to work, like "power on" led or load resistor

what is your ac voltage over transformer secondary

[w!ll]

"Both grounds are fine"

What do you mean, there is only one ground in that circuit

You can measure current separately on + and - sides, you need two multimeters or do first another and then another


I´m not sure but some regulators might need a small load to work, like "power on" led or load resistor

what is your ac voltage over transformer secondary

Sorry, I meant both ground terminals on the regulators were properly grounded. I'm using an 18vAC wall adapter. SO you can measure the + side and - side separetly in the normal way? Like this? Disconnect postive supply from common circuit, multimeter set to amps, red lead to postive output on power supply, other lead to the postive supply input on the common circuit? Is that right?

[Nasse]

http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

ummm this is simple circuit even me got it working, and did it twice. Even did a vero layout and it was tested twice as said. But I meant what your ac voltmeter says at the secondary, but looks like it is about what it gives when using 18 volts transformer if it is that +-28 something

but you should get voltages right first, no reason to take current measurement but perhaps you suspect overloading