Draper Expert 70052, Instructions Manual

– 16 –

Fault indicator on and no output 

− Over-heat protection has 

possibly been activated.     

− Switch off the device and then 

restart it after the fault indicator 

is off.

− Wait 2-3min without switching 

off the unit. The device may 

then naturally restore its self 

(the device of pure Argon arc 

welding does not have 

over-heat protection function)

− Inverter circuit could be 

defective.

− Unplug the power supply plug 

of the main transformer on the 

MOS  plate  to  restart  the  device.             

The previous steps have been 

taken to remedy the situation, 

but the fault indicator is still on

− Switch off the device and 

unplug the power supply plug of 

the HF arc striking power 

supply.
•   If the fault indicator is still 

on, it will indicate that some 

field-effect tubes on the 

MOS plate are broken.

− Find and replace them with 

ones of the same type.

•   If the fault indicator is off, it 

will indicate that the voltage 

rise transformer in the HF 

arc striking circuit on the 

power supply plate is 

broken.

− Replace.

The previous steps have been 

taken to remedy the situation. 

The fault indicator is off, but 

there is no output.

•   The medium plate 

transformer could be broken. 

Use an electric bridge to 

measure the primary 

inductance and Q value of 

the main transformer which 

should be L=0.4-0.7Mh.

•   Some the secondary 

rectifying tubes of the 

transformer could be 

punctured.

− Replace.

− Find and replace with the ones 

of the same type.