[SOLVED] 12v 1000w pure sine wave inverter fault

[byronboy]

Hi Guys. I,m in the middle of repairing a skytronic 12v 1000w pure sine wave inverter which originally came in with no AC output.With no circuit diagram to hand it can be tricky to fault find.The no output problem was caused by two s/c irf740s ,two s/c irf3205 mosfets,a s/c smd transistor and o/c 100 ohm smd resistor,both in the drive of one of the irf740s.This got it up and running but with 200v reading instead of 230v.It appears to use 3 switch-mode transformer circuits in a parallel configuration using a KA3525 smps controller ic.
LM324 quad high gain op amp ic.
EM78P458 8bit micro processor.
Any help would be appreciated.
Regards, Peter.

 

[ALERTLINKS]

Check for DC bus voltage which shoud be around 310V. Find the regulation loop going to KA3525 from here. See if you can adjust.

 

[byronboy]

Check for DC bus voltage which shoud be around 310V. Find the regulation loop going to KA3525 from here. See if you can adjust.

Hi.
After a quick voltage check on the KA3525 smps ic,I decided to change it.This in fact cured the lower than normal output reading and is now spot on.
Many thanks for your assistance.
Regards, Peter.