how to check lcd led power supply step by step

In lcd led tv there arfe two type of power supply 

  1. without PFC (power factor correction) 
  2. with PFC
  3. identification of without PFC 

1. in without pfc power supply in which power supply consist of single transformer 

2. this type of power supply in which all voltage come out at same type like 5v stb, 12v etc.

identification of with PFC

  1. With pfc power supply consist of three transformer 
  2. first one transformer use to make 5v stb 
  3. second use to boost 300 to 390v 
  4. last power  use to make linear voltage like 12v and 24v  

testing method

in testing method we test 5v and 12v only with bulb load 

steps fallow 

  1. take one 12v bulb which is use in bike side light indicator 
  2. first check 5v stb place 12v bulb on 5v stand supply and gnd. then see bulb is glow dim it mean 5v stb is ok 
  3. if bulb glow dim but it goes to continuous on and off it means your 5v stb supply is not ok 
  4. then you have to work on stand by circuit problem check all the component related to stand by circuit 
  5. if 5v is ok then next step to check 12v  supply 
  6. place 12v bulb on 12v supply.and then 5v stb is sort with PS-ON OR STB ON then . if bulb is glow proper then you 12v supply is ok 
  7. if bulb is glow and continuous blink then check first check pfc circuit 390v is come on primary side main capacitor or not 
  8. if 390 is not come then check pfc circuit first .if pfc is ok then problem is shift to linear circuit 
  9. then check feedback line and linear circuit related component 

thanks for reading