Hi All, I have a vizio e550i-b2e that has no standby voltage. I am hoping some one can help. I am getting 10-14volts bouncing at pin 5 of ic901 (Vcc). According to the data sheet for that ic I need atleast 16v for it to turn on. I did a thermal scan and the only thing that glowed was d901.
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Vizio E550i-b2e no standby voltage
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Re: Vizio E550i-b2e no standby voltage
D950b is right by connector cn101, looks like they did not use D950a.Last edited by nomoresonys; 03-13-2022, 04:30 PM.
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Re: Vizio E550i-b2e no standby voltage
No everything looks good. From my understanding the ic takes current for the drain pins 7 and 8 and applies it to start the pwm then charges the cap for vcc. Then the aux winding is suppose to take over. However like I said the Vcc doesn't go over 14.5v and it needs 16 to turn on.
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Re: Vizio E550i-b2e no standby voltage
The vcc voltage you are seeing on pin5 is likely from the internal startup cell, Check the source resistors, R907a,b if they are ok, I suspect the ic itself could be bad, if it was trying to start you should see a volt or two on D950b as that is the output of the standby voltage, just be sure there is no short on the standby output killing the voltage
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Re: Vizio E550i-b2e no standby voltage
Originally posted by Mbd3 View PostI have put 3 ics in so far same results. I had the 5v stand by and then gone and can't get back.
Check that you don't have an open transformer winding between pins 1&4 and also the output pins 5&7Last edited by R_J; 03-13-2022, 07:44 PM.
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Re: Vizio E550i-b2e no standby voltage
What was wrong with Q800 & R804A? they are for the pfc circuit not the standby circuit. however if Q800 was shorted it may have damaged ic801 and ic801's vcc voltage is supplied by the standby circuit D902 via the transistor connected to J14
Also if ic901's internal mosfet shorted, it may have damaged the source resistors or shorted zd909, zd909 would need to be removed to check it because it is across the low value source resistors R907.Last edited by R_J; 03-13-2022, 08:25 PM.
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