External power broken and vin not working but usb works ok

I have an Arduino UNo R3. It won't power up from the "Japan jack" power input.
Plugging in the USB works though. The usb does IMHO not give enough amps for the sensors I'd like to use.
I also tried to input 5V power through Vin and Gnd but get nothing. When using USB for rx/tx and power all digital/analog data pins and 3.3V work fine.

What I'd like is have USB connected for serial output debugging but use a better power supply.
What do I solder and where?

If I solder power in somehow I don't want to get into a situation where plugging in USB causes a conflict (two diffrent v+ and v-).

I am no using the RX/TX pins. I am also thinking that I could solder power from external source and use RX/TX for debugging.

Any pointers and info are appreciated

If the VIN pin is not working then you may have blown something.
You may require more than 5 volts on the VIN to get the regulator to supply enough voltage as it needs a little more to operate.

Also if you are overloading the pins with any high current requirements you may also cause further damage to the board so consider putting any items like that on thier own power supply with just a common ground back to the Arduino.

It sounds like you may have popped the voltage regulator already if the power jack does not work or the supply you have is simply not good enough to make it work properly.

Suggest 7 - 10 volts for the power jack