Hi All
My first post, so apologies if I didn't put it in the right place.
I'm fixing a treadmill that blew motor pwm IGBT and took out the driving circuitry as well. I have checked all of the passive components and they check out OK. how ever, no firing from UC3845. IGBT and UC3845 were replaced with new ones obviously

I gave noticed that it also doesn't have 5 volts on pin 8. What would cause this? Everything else seems OK.

Looking forward to many discussions

Thanks!!

 

Please take some clear photos and compress them to as 800x600 .jpg files. and upload them with the button Upload a File, thank you.

 

that is one of the most painful experience i have ever passed over....to me it is the following


uc3845 xx serious is being manufactured by hundereds of manufactures ....this ices depend on the resistance of the ic its self to deduce its start-up values so it can get its needed 8.5 8.6 8.7 depends on the ic

now slight;y differnet manufacturing process will lead to new ic wont work ...usually not because of bad ic but because of the new 3845
have differnet resistance than the old one ...here your only hope is to adjust the values of the start up ...though it is not much of suceess i have managed to fix one smps out of 3 ....some times the adjustment is not succeful because the ic will fail is the start-up resistors are too low