Before you connect the TRS connector make sure you measured correctly.

Thanks for the heads up. I'm pretty sure the center is negative.

A dual 12V power supply you could make out of a 24V power supply. There are also plenty of small dual power supplies on the market, even though the stable regulated power supplies are not the cheapest, so maybe you buy an unregulated with a higher voltage and put two voltage regulators at the output.

In order to make one out of a 24V supply by adding to voltage regulators, were you thinking of putting those inside the power supply or making a separate box to do the regulating?

Do you have any suggestions for places to look for a dual power supply? Most of the supplies I have found are open frame or really large stand alone units. I haven't seen any in a portable or "wall wart" form. If you have any suggestions, I'm all ears!

Yeh, I think we were splitting hairs here. There's only 3V difference between 9V and 12V. In this particular circuit I think 12V would do no harm.

OK, good to know!

Not really. We don't know the history in the product development. It is not unusual to change design specs after the board was printed.

Very good point! If only this thing could talk!

 

I haven't read all the posts, but I think this would satisfy your needs.

http://www.circuit-projects.com/pow...r-supply-by-lm7812-and-lm7912-regulators.html

Instead of the circuit as shown, I would put a .1μf cap on the output side of both regulators and change the .1μf cap on the input side to .33μf.

The output from the transformer could be a little less than 18 volts. To get the full 1 amp from each regulator, you will need heat sinks on them.

 

5th image down, where Vcc goes to the power switch. There is a power LED there, with a resistor inline with it to limit current. What is the value of the resistor between power and the LED?

Colors are fine, like brown red brown or whatever.

Ohms law and assuming 20mA LED current should let you know if it was designed for 9V or 12-13.8V

Disregard what I said earlier, the colors and measurement conclude that this is, in fact, a 10K resistor. Do you still think there is a way to determine the proper voltage using this, Ohm's law and the assumption of a 20mA LED?

I haven't read all the posts, but I think this would satisfy your needs.

http://www.circuit-projects.com/pow...r-supply-by-lm7812-and-lm7912-regulators.html

Instead of the circuit as shown, I would put a .1μf cap on the output side of both regulators and change the .1μf cap on the input side to .33μf.

The output from the transformer could be a little less than 18 volts. To get the full 1 amp from each regulator, you will need heat sinks on them.

Wow, that looks GREAT! I want to figure out how to make that thing!

Thanks for the design tips as well!

I think the device only needs about 300mA so do you think I'd be OK without the heat sinks? But then again, why not just put them in anyway...

 

Disregard what I said earlier, the colors and measurement conclude that this is, in fact, a 10K resistor. Do you still think there is a way to determine the proper voltage using this, Ohm's law and the assumption of a 20mA LED?...

The usual resistor value for running an LED from 9 to 12v is a few hundred Ohms. Assuming a volt drop of 2v across the LED & 20mA current, a series resistor of 10kΩ would require a supply of around 200v.

Somethings not quite right here! LOL.

Are there any other resistors connected to the junction of the LED & 10k resistor?