Question: What is the reason why the work light of the Santak 500VA inverter flickers with a tweet?

Label: Question: I have a Santak SANTAH500VA UPS uninterruptible power supply, which is normal when it is turned on. But after a while, its inverter working light flickered and there was a whining sound. What's the reason? Answer: We know that whether SANTAK 'UPS' 500VA uninterruptible power supply is powered by city power or inverter depends on the RS trigger composed of two NAND gate components of IC5. Please check if there are any of the following conditions? When supplying power from the mains, RS flip-flop VH u003d '1Low level, VG is high level, then measure the reset terminal R (VF) is low level, all are wrong; set terminal S (VN) is a series of positive pulses, correct; IC3 pin ⑧ is high level ,correct. The test mains detection voltage V1 is 0v, that is, there is no mains detection voltage, and the secondary winding of the test transformer T2 is open. If there is, the transformer T2 can be replaced, and the work can be normal.