Vizio VW42L problems

[martyparish]

Re: Vizio VW42L problems

The transformers are the two large black components.

[chopsawkev]

Re: Vizio VW42L problems

If I unplug bother inverters, and disconnect the boards from the chassis, with only the ribbon connector between the two, i still get ground at the 24v pins on the slave. that can only lead me to believe that the ribbion connector that runs to the TCON is what's providing ground. am i chasing my tail here? is there supposed to be ground there?

[chopsawkev]

Re: Vizio VW42L problems

also how do i check the transformers?

BET 2544 42l3 bja2c07a12 is the part number.

[budm]

Re: Vizio VW42L problems

Is the PS_ON staying at 3.1V when it the 12v/24 are gone? That PS_ON has to be there when the TV is powered up, if the PS_ON goes away, then the main board has gone into shutdown. If it is there but the 12v/24v go away, then you need to troubleshoot the power supply. Disconnect the cable from the power supply to the inverter board (if the PS_ON is OK) and see if the 12v/24 will stay on. I still do not like the voltage reading of the LDO on the main board, they are showing bad. We need to get the 12v/24v to stay on first.

[chopsawkev]

Re: Vizio VW42L problems

budm,

ok so if the inverters are plugged in, voltage at PS_ON is 0V at standby, 3.1V at power. it returns to 0V when the tv goes back to standby (90 seconds or so). with the inverters unplugged, I get the same results. also with them unplugged, at power, I get the 12v to the main and the 24v to both inverters. the 12/24 go away when the tv returns to standby (still about 90 seconds or so).

However, with the power on now, the LDO's are yielding different, higher results. would you like me to do a rundown again on them all with the power on and the inverters unplugged?

[chopsawkev]

Re: Vizio VW42L problems

this is power on, inverters unplugged.

U2
AMC1117
F0734F
PIN1 2.01v
PIN2 3.26v
PIN3 5.08v

U7
AMC1117
F0734F
PIN1 .03v
PIN2 1.27v
PIN3 3.26v

U8
AMC1117
F0734F
PIN1 2.055V
PIN2 3.299V
PIN3 5.17V

U9
K1117S15
745
PIN1 0.003V
PIN2 1.5V
PIN3 3.26V

U33
AMC1117
F0734F
PIN1 2.02V
PIN2 3.26V
PIN3 5.08V

[selldoor]

Re: Vizio VW42L problems

The LDOs all look ok to me.

[budm]

Re: Vizio VW42L problems

They do look OK, so something is telling the main board to go into standby mode (PS_ON goes LO after about 90 seconds) by itself.

[MisterD]

Re: Vizio VW42L problems

Looks like the pairs of 680uf 35v Caps have been replaced on both inverter boards but the leads are left long and the caps themselves may be longer than the originals, in the pictures it appears that the body of one cap is laying on top of the legs on the other cap and could be shorting out, you may want to check just to be sure.

[chopsawkev]

Re: Vizio VW42L problems

Looks like the pairs of 680uf 35v Caps have been replaced on both inverter boards but the leads are left long and the caps themselves may be longer than the originals, in the pictures it appears that the body of one cap is laying on top of the legs on the other cap and could be shorting out, you may want to check just to be sure.

i replaced them, i push them up and no change.

any suggestions on what might be telling the set to turn off? how do i cehck the inverter transformers?

[MisterD]

Re: Vizio VW42L problems

I noticed in your pictures that the mounting screws are missing on the T-CON Board, make sure these are installed, and then tighten (snug) down all others on every circuit board, these are needed to ensure good ground connections, if that doesn't correct the problem,with everything else connected normally disconnect the T-CON Board from the input side ( the 2 bottom connectors) and see if it will power on and stay on longer than 90 seconds and if you get normal voltages then.

[chopsawkev]

Re: Vizio VW42L problems

hey guys, sorry i had a busy weekend. Ok so ive reinstalled all of the board screws and snugged up the rest. ive disconnected the tcon from the rest of the tv and im still getting the voltage drop and the TV is returning to standby after 90 seconds.

Still the only way for me to get regular voltage to the main board is when the slave is disconnected. im going to try disconnecting the master from the slave and see if i still get the voltage drop at the main.

[chopsawkev]

Re: Vizio VW42L problems

so no change when the master and slave are separated. the only time i get normal voltage is when the power to the slave is removed. and when that is removed, the pins providing the slave with power seem to be normal ...

[chopsawkev]

Re: Vizio VW42L problems

ive got the slave off and in my hand. I've checked a cross the caps, and im getting continuity between the positive and negative. i removed the caps and checked the board and im still getting continuity between positive and negative. im guessing this is where my problem is. now what on the board could be bad? i dont visually see anything wrong and with it and im guessing it will be hard to test if everything is grounded out? again im just shooting from the hip here, i dont really know what im doing, please correct me if im chasing my tail ...

[MisterD]

Re: Vizio VW42L problems

But with the Slave board removed and the TV Powered on does it still go back into standby after 90 seconds? you may have indicated this in a previous post but I'm just double checking. Thanks.

[chopsawkev]

Re: Vizio VW42L problems

yes, it still returns to standby.

[MisterD]

Re: Vizio VW42L problems

I'm not sure why it goes into standby in 90 seconds, it sounds like the slave inverter board definitely has a problem, visually inspect it for solder shorts that could have happened when you replaced the caps.
In post 1 you said you got this TV from a friend, do you know if he or anyone else attempted any repairs before you got it from him? I'm wondering if you have two different problem areas.

1. The Slave 2. Main Board or a short circuit somewhere else such as a ribbon cable or wire with insulation cut and wires touching or grounding, I would visually inspect everything you can, even looking for things like a loose screw lodged on a board somewhere and creating a short.

[johnboy1313]

Re: Vizio VW42L problems

Have you unplugged the panel from the T-Con or unplugged the T-Con from the main, and then tried to power up? Have you used a resistor to force the PSU on?

[chopsawkev]

Re: Vizio VW42L problems

My friend did not attempt to fix it nor did anyone else. He said that he bought it new.

He said that when it went he heard a pop, then no screen. he didnt say whether or not it went to standby (this was months ago)

I thought I might have shorted the board out, everything looks good though. I wicked the solder up and im still getting the short.

I cant see anything totally out of place, I've been looking all over. I can hear the PSU buzz when it starts up though. also the LED on the master lights up and then fades away. the light on the optical port stays on until the 90 seconds are up.

Johnboy, ive done both of those and i still get the same results.

how would i do that with a resistor?

thanks again for all your help guys, i really appreciate it.

is it possible that if the screen doesn't come on that the TV would just shut itself down?

[budm]

Re: Vizio VW42L problems

ive got the slave off and in my hand. I've checked a cross the caps, and im getting continuity between the positive and negative. i removed the caps and checked the board and im still getting continuity between positive and negative. im guessing this is where my problem is. now what on the board could be bad? i dont visually see anything wrong and with it and im guessing it will be hard to test if everything is grounded out? again im just shooting from the hip here, i dont really know what im doing, please correct me if im chasing my tail ...

OK, so what the Ohm reading that you are getting across the pads of the cap, at this point we are not sure if it is 1 Ohm, 1K Ohm. Do you know what Ohm scale you are using? If it does show around 1 Ohm reading, then please take good close up picutres of this Slave inverter board in two sections so I can really see the component and labels of the components.