. This machine used in power supply models for 486 PL37A - 0070, measured the power board plug-in X906 SVSTB voltage ON the ON/OFF voltage is normal, about 4 v, 5 VDC voltage 12 VDC output, X90224VDC no output, 18 VDC output. The machine power supply detachable plate maintenance alone, between 5 VSTB with ON/OFF of the X906 jumper 10 k Ω resistance can forcibly boot. The power supply board maintenance and testing point below. Measuring 24 VDC on instantaneous output, then fell back. Release 12 VDC or 5 VDC N907, N908 step-down module, the overvoltage protection SCR D927 tear down, momentary boot 24 VDC output is normal. 24 VDC power supply, and before all normal, successively connected to D927, N907 output is normal, but when N908 5 VDC step-down module is connected power supply overvoltage protection. Replace step-down module N908 fault repair after (LM2576-5). hyqservice manual download site
 hyqservice manual download site
Tip: LM2576 output voltage is 3.3 V, 5 V, 12 V, suffix should pay attention to when the voltage is consistent.hyqservice manual download site