长城电源维修关键测试点(外国英文资料).docVIP

长城电源维修关键测试点(国外英文资料) Great Wall power supply key test point   1, KA7500B feet (power supply foot) : 12 normal data: + 12 v + 20 v or so, a few machines 26 v is normal.     2, LM339N 3 feet (foot) PG output: normal data: 5 v     3, KA7500B 8, and 11 feet (half bridge driver output) : normal data: + 2 v or so     4, KA7500B foot protection (foot) 4: normal data: 0 v, such as 3 v, the circuit in the protection state.     5, KA7500B 13, 14, 15 feet internal output pin (IC) : internal output 5 v.   Great Wall series power supply IC exchange table:     TL494 / KA7500B/BD494 / BDL494 S494PA/IR3M02 / MB3670 / MB3759     / MST894C/TL594 / ULN8186 DBL494 / ULS8194R/IR9494 / UPC494     UA494 / TL494CN   Heres a little more detail:     offline standby, two large after testing rectifier filter capacitor should have + 300 v dc voltage, ATX14 feet (the green line, PS) there should be a 5 v LM339 13 feet (PG) should be 0 v, ATX purple line should have a + 5 v, the other foot to 0 v. Short after green, black start power supply, ATX green line to 0 v, PG is 5 v, at the same time the output voltage of the ATX other foot should be normal. Continue to measure should be 12 feet of power supply of 7500 or 494 feet - 20 v dc 12 v power supply, 13, 14, 15 feet should have the 5 v output from the inside, 4 feet (dead zone, protect the foot) normal to 0 v, 8 feet, 11 feet should be 1.5-2 v driving voltage output. Which point voltage is wrong, check the relevant circuit, can find out the fault components.    Some common faults   add site:     1: insurance power cut   Level before   varistor, rectifier bridge, filter capacitor, two power tubes, backup power supply of power tube, first check whether the short circuit     2: electricity 300 v high voltage     check 5 VSB for output, if yes, then check switch power supply voltage controller 4 foot, so 4 v, power protection, check the voltage sampling resistance and LM339, but experience, fa