The tl 494 ic is not giving the required 5 v to the base of output transistor the ic is new and is powered by 620 k ohm resistor

 

is powered by 620 k ohm resistor

Where is this 620k resistor connected?
Can you give us a schematic of your supply, please?

 

Here is a typical TL494 schematic:


Are you refering to the ref voltage 5V at pin 14? Or the voltage at P8 and P11.

Is your 620K resistor referring to "RT" on P6 of the chip?

 

From previous posts on this chip the 620k is off the rectified incoming AC gives approx 7 - 8v at pin 12 before the inverter starts and then a secondary winding on the flyback transformer generates 12v or so via a half-wave rectifier/smoothing capacitor...

eg like the 56k shown here... but for 370v off a 240 rail...

 

The tl 494 ic is not giving the required 5 v to the base of output transistor the ic is new and is powered by 620 k ohm resistor

Post your circuit diagram please.