Reverse engineering old record player schematic
I redrew your circuit with corrections to match the board photos, and it turns out to be a fairly conventional class AB audio power amp. 

The pickup is probably a ceramic cartridge which has high impedance, so Q1 and Q2 are arranged in Darlington configuration to give a high input impedance. R1 raises the input impedance even higher, and keeps it high at lower volume settings.     

R2 baises Q1 and Q2, with negative feedback to stabilize the DC operating point. R7 applies AC negative feedback to reduce distortion. D1, R4 and R6 bias the complementary output transistors slightly on to reduce crossover distortion.

The volume potentiometer is wired 'backwards' to provide constant DC bias at all volume settings. If the pot track or connections break or short out it could upset the bias, causing the voltage on R6 to go close to the supply voltage or ground rather than about half the supply voltage.

I can see some flux between the pot center terminal and ground, which might be hiding a short circuit. I would clean between any pads that don't have a clear open area between them. Some solder joints look partially cracked, so I would re-solder all of them. 

If the DC bias point is correct and the output capacitor is good then you might just have a bad cartridge. To prove this, disconnect the input and inject a test signal (eg. mains hum from your finger) to see if the amp is working.