Optocouplers pc123

[Chicd]

Have several power boards that have no power/voltage to the 'cold'side....could the pc123 optocouplers be the cause?
Tried testing and think I have several that are bad...any hints?
Have no voltages on the main board other than standby...

Still learning....

[budm]

Re: Optocouplers pc123

Hard to help without full details and good clear pictures of what we are dealing with.
Makes and model?

[Chicd]

Re: Optocouplers pc123

Thanks Bud...
Vizio 37L HDTV10A
Standby ok (amber)
No power when switched on...have 5.2v all three pins on connector....no other voltages PB# 0500-0507-0250
MB#3637-0072-0150(2D)...F1-0v F2-5.2v
U8 tests Ok...5.2/3.3/2.1
U33,7,9,2 all 0v

Slowly learning...have several Vizio's with same symptoms...does the 'cold' side of PB remain 'cold' until the main board sends it a signal to 'turn on'?
Guessing my problem may be in the MB...
Thanks for your willingness to teach...
Chic

[stj]

Re: Optocouplers pc123

they can fail - or be killed.

[dskall]

Re: Optocouplers pc123

Need voltages from connector that goes from power supply board to main board. Will need pin#- PIN DESCRIPTION -Pin voltage in standby-Pin voltage when pushing power button and picture of connector on power supply board.
Format:
Pin# - Pin Description - Pin Voltage standby - Pin voltage power on
1 - XXXXXXX - XXv - XXXv
2 - XXXXXXX - XXXv - XXXv
3 - XXXXXXX - XXXv - XXXv
4 - etc.

[Chicd]

Re: Optocouplers pc123

Thanks for replies....
Voltages on connector from PB to MB
1-pson-0
2-(12v) 0
3-(12v) 0
4-(12v) 0
5-blank
6-gnd
7-gnd
8-gnd
9-(stby) 5.2
10-(stby) 5.2
11-(stby) 5.2
12- (A) 0
13-(B0 0

Same after pushing power button...

[dskall]

Re: Optocouplers pc123

Disconnect connector from mainboard side and insert 1k resistor from Pin1 to pin9 see if you get your 12v

[Chicd]

Re: Optocouplers pc123

Will do tomorrow...

[Chicd]

Re: Optocouplers pc123

After inserting resistor....what if I do/do not get the 12v?

[budm]

Re: Optocouplers pc123

If you are able to force on the rest of the power supply using the resistor then it means the power supply is OK, just make sure you disconnect the cable going back to the main board first before attempting the force on.
So far it looks like you have main board problem because it is not sending the PS-ON to turn on the rest of the power supply.

[Chicd]

Re: Optocouplers pc123

OK...I replace quite a few 1117's in Vizios