General ? concerning PS_On and other DC voltages from PS to MB

[Nick's Tvs]

Re: General ? concerning PS_On and other DC voltages from PS to MB

ok so that question got answered pretty quick. Stopped working. So it looks like Q5 is no longer giving out any voltage and neither is the PS-ON when I press the power button. I just get 0v no matter what. 5 volt line is still active but that's it. I unplugged it and left it unplugged for the last 15 minutes, and it seems like that may have gotten it back to square one with the 1.2 volt appearing again and the 3.2 appeared again. But it seems like if I do this jumper and keep the tv on, the board doesn't like it and just shuts down pretty much for a while.
Thoughts?

[Nick's Tvs]

Re: General ? concerning PS_On and other DC voltages from PS to MB

So this is what I found out. I can turn the tv on and off as many times as I want with the mod. But if I unplug and plug it back in, the tv is inoperable for about 4 or 5 minutes maybe less. I am thinking the vizio logo actually is "blinking" like some vizio tvs do when you first plug them in, and is initializing before I can turn the set on. So the mod actually does work fine I think.

[budm]

Re: General ? concerning PS_On and other DC voltages from PS to MB

If that Q5 Collector is at 0V then I do not think it is related to what you are seeing then since is not active when it is at 0V, you can verify again as to what Collector Voltage is when you unplug and replug the power back in. Q5 may be doing some kind of reset when TV is unplugged and plugged back in.
If that is the case then we need to find other Active device that can be used as a source for the PS-ON signal.

[Nick's Tvs]

Re: General ? concerning PS_On and other DC voltages from PS to MB

Also additionally the IR sensor does not turn on meaning I can only use the buttons on the side and the remote does not work with the set.
the IR connector J6 is the bottom one left right next to the logo connector J5 that goes from amber to white when turned on. Neither of those are activating. The logo stays a very dim amber with .9 v going to it and the infrared sensor gets 0volts no matter what.

[jts1957]

Re: General ? concerning PS_On and other DC voltages from PS to MB

I also had a VF550M (Main= 3655-0062-0150 (4C)) with 1.2 volts at PSON. Applying 3.3 volts from an external power supply would allow the set to work.

Trying to follow a foil trace that at times feeds through from one side of a PCB to the other is a challenge. Best I can speculate is a pin on the large heat sinked (Micro?) puts out a voltage that goes to R11/C19 junction AND along the way heads over to Q5 base/Q7 collector.

Anyway, checking for a convenient point that has zero volts with the set OFF and 3.3 (to 5) volts with the set ON led me to U9 (VIN pin - 3.3 volts). Soldering a jumper wire between that pin and R11/C19 junction allows PSON to turn Power supply ON/OFF as required.