vizio 50in plasma psu problem

[shawt99]

hello everyone i am currently working on a vizio jv50phdtv10a with power supply aax30284301. for some reason when i test to voltages at the connectors all of the 5v supplies are putting out .81 volts instead of 5 volts. the p.o. attempted to replace the caps on this board and im pretty sure caps 285 and 287 are wrong, if anybody knows the values of those caps and any ideas as to why the 5v connects are only reading .81 volts that would be great. thank you in advance.

[R_J]

Re: vizio 50in plasma psu problem

What makes you think the caps are wrong? post some pictures so we can see what you are talking about.
The 5 volt standby comes from T501, the smps ic is U501, What voltage do you have across C522? You should have about 160v dc, If you have 160v, unplug and check the resistance of R510, if it is open, U501 is bad.
C287 is 470uf likely 25v C285 could be around 100uf or less likely 25v also

[Andrew F. Ali]

Re: vizio 50in plasma psu problem

what makes you think the caps are wrong? Post some pictures so we can see what you are talking about.

+100

[shawt99]

Re: vizio 50in plasma psu problem

at the moment 285 is a 10v 3300uf and 287 is a 10v 1000uf so id say something is wrong there lol. heres a couple of pictures

[R_J]

Re: vizio 50in plasma psu problem

Here is the shopjimmy picture, those caps are indeed wrong but not the cause of the missing 5 volts. What is the part number on U501?

[shawt99]

Re: vizio 50in plasma psu problem

just got done swapping those caps out and taking some measurements. C522 does in fact have 160v across it. Actual reading was 161.3v

[shawt99]

Re: vizio 50in plasma psu problem

str w6251

[shawt99]

Re: vizio 50in plasma psu problem

my 5v standby voltage is there. the reading on that was 4.91. its the 5v to the mainboard and ysus board that is only reading .81 both are labeled as 5vsc.

[R_J]

Re: vizio 50in plasma psu problem

Ok so you have +5v standby going to the mainboard, good. Do you have any voltage on RL-ON when you press the power button, or can you hear the relay click when you press the button?

[shawt99]

Re: vizio 50in plasma psu problem

no sorry, i have 5v standby on the psu. the 3 5vsc pins that send 5v from the psu to the mainboard are only sending .81 instead of the full 5v. so the mainboard isnt getting the required voltage.

[R_J]

Re: vizio 50in plasma psu problem

So you are getting RL-ON voltage from the main????

The 5V standby that supplies the main board, and runs the processor, when you push the power button the processor outputs a logic level to RL-ON, that turns on the power supply and THEN you get the other voltages like the 9Vsc, 5Vsc etc.
Once you have those you will get the VS-ON conmmand from the main to turn on the VS & Va

[shawt99]

Re: vizio 50in plasma psu problem

yes i have RL On. thats reading 4.39 volts. no relay click on the psu however.

[R_J]

Re: vizio 50in plasma psu problem

It could be that the RL-ON line needs to be taken low to turn on the power supply.
If you disconnect P800 from the main is the RL-ON still high? if it is take it to ground, you should here the relay turn on.

The section of the power supply that gives you 5Vsc comes via D271 from the secondary of T112, for T112 to operate requires U151 and Q151 to drive it. Which requires voltage that is across C603, which comes from D101 bridge rectifier, The ac for the bridge is fed via RL102 and the two green thermistors TH102 and TH101, which will get shorted by relay rl101.

[shawt99]

Re: vizio 50in plasma psu problem

sorry for the delay, i had some time to mess with the set again and you were absolutely correct, when p800 to main is disconnected the relays click on. so something on the main is stopping the psu from powering on? i have had a case with this set before where the main would keep blowing up. the set would run for 10 minutes or so and then no sound and no picture.