Unknown circuit analysis

[bmandl]

Hello,
I got some pcb circuit to repair it because it is not working anymore. I already figured out that transformer is broken, but now I want to know, what does this circuit even do. It is supposed to hold switch on for differend amount of times but I don't know how this is done. I drew schematic from pcb. Can someone please look at it and try to explaint it to me. Thank you.

 

[andre_luis]

The relay contact at transformer secondary side seems does not make sense, due it is controlled by transistor output, which interrupts its biasing current.

Except it, seems to be a primitive control for over voltage, interrupting the power leading at output just under a certain limit defined by potentiometer.

By the way, the secondary side is drawn inverted on orientation.

 

[D.A.(Tony)Stewart]

Ignoring a few schematic errors with polarity, it appears to be a BROWN-OUT RELAY cutout circuit or some threshold set to determine when the Aux AC outlet gets the power Relay activated. The transformer only supplies power to the relay coil and transistor drain is negligible, so there is no obvious heat failure mode, other than a short circuit.

The capacitor bridging primary to secondary seems in error and isolation breakdown voltage should be rated for >3kV.

 

[betwixt]

The reservoir capacitor is shown reversed but I suspect the one bridging the transformer is shown incorrectly wired. My guess is the positive side goes to one side of the variable resistor. If there is a capacitor across the transformer it should be a special high voltage rated type and not polarized.

Brian.

 

[bmandl]

I will recheck the circuit for and correct possible errors. Thank you all so far for your answers.