Vizio VP504FHDTV10A Won't power on

[creatorc]

Hello and Happy New Year everybody! I'm trying to fix a Vizio plasma that won't power up anymore. The Vizio symbol stays amber when you press the power button, and clicks, then about 3 seconds later it clicks again. There is 5.1v on the standby, and when you press the power button the ps_on goes to 4.8 volts (supposed to be 3.3v) so I'm going to replace the LDOs. My first pressing question, I guess, is there anything that may have been damaged by the ps_on being up at 4.8 volts? I looked over the caps and none of them are bulged. I checked the caps on the power supply board and the esr is < .5 ohm (using a homebuilt esr meter) and none were more than 25% out of spec. What complicates this repair is that the unit is too heavy for me to bring to my workbench, so I have to travel about 35 miles each time I work on it. The 3 LDOs are K132 G1117 (no suffixes) so I'm assuming they are the adjustable variety. I would be very thankful for any insight anyone has.

creatorc

[PlainBill]

Re: Vizio VP504FHDTV10A Won't power on

Hello and Happy New Year everybody! I'm trying to fix a Vizio plasma that won't power up anymore. The Vizio symbol stays amber when you press the power button, and clicks, then about 3 seconds later it clicks again. There is 5.1v on the standby, and when you press the power button the ps_on goes to 4.8 volts (supposed to be 3.3v) so I'm going to replace the LDOs. My first pressing question, I guess, is there anything that may have been damaged by the ps_on being up at 4.8 volts? I looked over the caps and none of them are bulged. I checked the caps on the power supply board and the esr is < .5 ohm (using a homebuilt esr meter) and none were more than 25% out of spec. What complicates this repair is that the unit is too heavy for me to bring to my workbench, so I have to travel about 35 miles each time I work on it. The 3 LDOs are K132 G1117 (no suffixes) so I'm assuming they are the adjustable variety. I would be very thankful for any insight anyone has.

creatorc

I wouldn't be concerned if PS_ON is above 3.3 volts; all it
s doing is turning on an opto-isolator.

The usual troubleshooting process on a plasma TV with these symptoms is to disconnect the cable from the power supply to the Z-Sustain (right side as viewed from the back of the set) and try to turn the TV on. If it doesn't turn on, disconnect the power cable from the Y-Sustain (left side of the TV as viewed from behind), reconnect the power cable to the Z-Sustain, and again try to power it on. If it fails to turn on, try disconnecting the power cables from both sustains. If the power supply still does not come up and the output pins of the power supply are labeled, check the voltage on each of those pins.

I had a similar problem with a Philips set; it turned out a DC-DC converter had shorted and overloaded the 12V output of the power supply.

PlainBill

[Village Electronics]

Re: Vizio VP504FHDTV10A Won't power on

Hello and Happy New Year everybody! I'm trying to fix a Vizio plasma that won't power up anymore. The Vizio symbol stays amber when you press the power button, and clicks, then about 3 seconds later it clicks again. There is 5.1v on the standby, and when you press the power button the ps_on goes to 4.8 volts (supposed to be 3.3v) so I'm going to replace the LDOs. My first pressing question, I guess, is there anything that may have been damaged by the ps_on being up at 4.8 volts? I looked over the caps and none of them are bulged. I checked the caps on the power supply board and the esr is < .5 ohm (using a homebuilt esr meter) and none were more than 25% out of spec. What complicates this repair is that the unit is too heavy for me to bring to my workbench, so I have to travel about 35 miles each time I work on it. The 3 LDOs are K132 G1117 (no suffixes) so I'm assuming they are the adjustable variety. I would be very thankful for any insight anyone has.

creatorc

Be aware that there have been many cases reported of failed components in the DC-DC converter section of the main board.

[creatorc]

Re: Vizio VP504FHDTV10A Won't power on

Since I have the Main board at home (I was going to change the LDOs, how would I verify/check the DC-DC converter? I'm assuming it is the section in the upper right corner of the board (pics atttached, I hope)

creatorc

[creatorc]

Re: Vizio VP504FHDTV10A Won't power on

Ok, I've got the whole TV at home and found that if I disconnect the line from the power supply that goes to the Y sustain board, I can get the power supply to come up a little farther. It still wouldn't bring up the 15 volt line, but that could be from the Y sustain not sending back it's power up line. Checking the diodes, I found 2 3 terminal units shorted. They are D421 and D422 (D421 is circled and D422 is on the back of the heatsink behind D421) and are labeled MA3DF40. I can't find any info on Google about them and FindChips doesn't find anything either. Does anyone know of a replacement for these?

[PlainBill]

Re: Vizio VP504FHDTV10A Won't power on

I got 1400 hits when I googled MA3DF40, including datasheets. They ARE marked as obsolete, but here is the PDF. After you learn to use Google, perhaps you can match the parameters.

PlainBill

[creatorc]

Re: Vizio VP504FHDTV10A Won't power on

Ok, my fault. A juxtaposition of the 3 and D (was typing MAD3F40) and now I get them. I thought it was odd that I found datasheets for the MA3DF46 (there are some of those on this board too. Now just have to wait for them to arrive for installation.

[creatorc]

Re: Vizio VP504FHDTV10A Won't power on

Ok, this tv has the Panasonic ETX2MM704MGN power supply, but I never get Vda out of it. I've checked pin 14 of MC701 and it never drops down to the 3.5v (from 4.99v) to turn on the optocoupler. Which means it never gets the 4.0v feedback from Vda. I also don't get the Sub Out on pin 10 (should be 3.8v). Am I not getting the Vda on signal because the Sub Out is missing? The Vsub Power Control on/off pin jumps up to around 13.7 volts for a few milliseconds (should be 3.3v), then drops down to about 0.3v for a few milliseconds then jumps back up around 12v. The relays turn off and the voltage decays down to 0.0 again. After the relays shut off I do get a repeating series of 6 low going pulses on pin 18 PS_SOS of the MC701, if this helps at all.