Newbie needs help wiring a preamp for acoustic Yamaha pickups already installed.

[IrishLuck]

Hey everyone,
I'm new here. Looks like I found the right place to get some help. I've had this guitar for a long time. When it was given to me the person had dropped it on the strap button input jack. And she had taken the wires out from the preamp. I was given a nice Acoustic AG30 amp and thought I would just plug in my guitar using a Dean Markley ProMag (the kind that goes in the soundhole) and found out since it's passive that I'll need to buy a preamp. So it got me looking at my guitar. There's a nice preamp and pickups already installed. Everything is hooked up, well almost. The 9v power source to the preamp is hooked up, the pickup wiring to the preamp is also hooked up, it's just the output jack wiring (ring, tip, sleeve) wires that need to be hooked up. I found a 3-pin plug that fits into the input of the preamp perfectly, but how do I figure out what order I put the red, white and bare wire that go into each of the three pins? I can't find a schematic. Best I can find it that it's a "System 34 preamp" from a LW5C Yamaha acoustic.
I messed around with it a bit yesterday and got it to work, but it also works with the polarity switched (red and white wires). I know I probably shouldn't have done that, but thought it might just be stereo right and left, and wouldn't cause any issues. It functioned properly and sounded great. The EQ worked, mute buttn worked, and the battery led as well as both gain knobs. Everything worked, so should I go ahead and solder it together or do some tests first to make sure it's wired correctly and nothing gets damaged?
Ring, tip and sleeve connnections from a 1/4 inch instrument jack I always thought were just ground, right and left stereo. Am I wrong?
Here is a photo of the front and rear of the preamp. Not that it wil help, but maybe someone has one like it...
Thank you for any advice/ideas/suggestions...

[mr fab]

you will find that the extra lead usually connects the battery when you plug in. this is usually connected to earth from the using the sleeve of the plug to make the connection. it seems you have hot signal wire sorted out, so its just a case of working out which is which for the earth and power, which I suspect will not make much difference.

to be sure, you may wish to put an ammeter on the one of the battery terminals and check that current is flowing when plugged in and also not when unplugged.

[the great waldo]

you will find that the extra lead usually connects the battery when you plug in. this is usually connected to earth from the using the sleeve of the plug to make the connection. it seems you have hot signal wire sorted out, so its just a case of working out which is which for the earth and power, which I suspect will not make much difference.

to be sure, you may wish to put an ammeter on the one of the battery terminals and check that current is flowing when plugged in and also not when unplugged.

Hi Use a multimeter to check continuity between battery clip -v and one of the pins on the connector, thats going to be the one for the middle contact on the jack socket. The other pin on the connector that is the main earth you can check by connecting part of the metal case and the remaining pin. It does make a difference if the earth and middle contact are reversed on the jack as the battery will always be on if you have them wrongly connected.

Cheers

Andrew