Leds in 2006 gmc sierra radio

I have already changed all my interior lights to leds, gauges, four wheel drive switch, headlight switch, door switches, fog and cargo light, steering wheel lights and ac control lights. So I decided to change radio lights to leds. I have gotten the circuit board out of radio and all the lights removed. I couldn't find anything on the internet about which points on radio were negative and which were positive. So I plug radio back in and had just took a led with a solder resistor on it and just started touching the light to the points to see which ones were which. I got nothing on most of them except on one point in the middle set of points on circuit board the led lit up a little bit. Does anyone know or can tell me which are which? Are the not working cause I have all the lights removed? Do they light up in curcuits? Meaning if one is out they will all be out? Any help is appreciated.

So I finally found one posting on the internet that had polarity info for the radio for changing to leds. I soldered my leds to the circuit board using this diagram and some of them worked and some didnt. Also some of them were flickering. On top of the flickering the leds stayed on even when truck wasnt running and lights were off. I still am looking for some help as my radio is still tore apart. Also one guy on the same forum I found the diagram had said that the points on the circuit board were a awkward series circuit with 2 series/parallel circuits with polarities colliding. It doesn't make sense electrically but it works. Does that mean each individual led doesnt need its own resistor? I put a resistor on every led like you would the cluster or heater controls. Any help is appreciated.