Vizio VW37 Power Supply PSON working but no 12v or 24v output

[budm]

Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

You can check MOUSER, for example:
http://www.mouser.com/Passive-Compon...+10+UF&FS=True

[tibimakai]

Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

I'm working on an exact same TV and I have almost the same issues/symptoms as you, the only difference is that I have the 12/V.
you are doing a great job describing everything as you go along.
I'm new in this field and I'm in the learning phase.
I have just measured those caps, and mine are OK.
with the board disconnected they show on a 20K range a 55.4kohm.
I have removed the PS_ON wire and on mine too the 3.31V came back.
How much it should be the voltage for A and B which goes to the inverter? How did you tested the inverters?
If I disconnect the the T-con cable the same backlight blink comes on and PS_ON is still 2.16V.
I guess I will have to test the PS_ON w/o T-con connected.

[tibimakai]

Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

I have disconnected the inverters, T-con and the PS_ON still drops to 2.16V.
So something is wrong in the power supply.
If I unplug only the PS_ON wire from the connector, I have 3.31V on that wire. So from the main is coming the right voltage. Or it could be that under load one of components acts weird.
If I remember somebody replaced the Q26 transistor on the main board next to the connector and it fixed his TV. Not sure if it's related to our case or not though.

[Tetranitrate]

Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

I didn't do too much testing on my inverters. With just the power supply and inverter connected, I externally triggered the PSON with a pair of AA batteries and the power supply output the correct voltages, so I figured everything was ok.

I do not know the voltages for the A and B lines, but can check once I take apart my TV again to replace the capacitors on the display board.

I have attached the datasheet for the display board that was in my 37 inch Vizio. It gives some specs for things other than just the display board, the one that caught my eye was some specs for an inverter board. Now, while the inverter board that is in my TV is made by a different company, I would not be surprised if the specs for those lines were the same. That is:

※1: Connection of brightness control terminal
Bright control by the voltage
0V : Min. brightness
3.3V : Max. brightness
※2: rise time must >20 ms
※3: BLON Logic
H(5V) : Back Light ON
L (0V) : Back Light OFF
OPEN : Back Light OFF

Although if you were able to find a datasheet for your inverter board then definitely use those ratings instead.

For my repair work, I broke down and ordered the recommended 15uF 25v caps recommended by budm and tom66 in previous posts. I figured, while it would be fun to do my repairs with stuff I had laying around, there might also be other things potentially wrong - so I should just be definitive about my repair instead of using parts that could introduce unforeseen problems (thereby masking other possible issues).

[Tetranitrate]

Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

I have disconnected the inverters, T-con and the PS_ON still drops to 2.16V.

If you can get a 3.3v DC source (I used a pair of AA batteries and soldered some wires to the power supply board), I would highly recommend removing the power board from everything and applying the 3.3 volts to the PSON line. It seems like it would give you a definitive answer as to where the problem originates.

[tibimakai]

Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

my problem is that I'm getting the 12 and 24v even like this, with low PS_ON.
How is that possible?

[budm]

Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

Hook up two 12v lamps (1157 car lamps or similar) in series and attach to the 24vdc output, if you truly have 24vdc the lamps should be ON.
The inverter needs 24vdc main voltage and 3.3~5vdc for the BL_on signal.
See example:
http://s807.photobucket.com/albums/y...%20SV470XVT1A/

[PlainBill]

Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

my problem is that I'm getting the 12 and 24v even like this, with low PS_ON.
How is that possible?

There are several different designs for the PS_ON input. In some cases it is nothing more than a NPN transistor with a resistor from the base to the PS_ON pin. On that design the threshold is less than 1 volt.

PlainBill

[DFH]

Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

Hello all, I am new to the forum and I am trying to troubleshoot the same DPS-247AP B power supply card on my 37 inch Vizio (model VX37L HDTV10A).

The symptoms are: logo light illuminates white, backlight comes on then goes out within 1-2 seconds, then logo light illuminates yellow, end.

After selecting the TV power button to ON, I checked the Power supply board connector CN03 that has the PSON pin and the 5VDC pins which measure very close to that value (~4.75 VDC). The problem I have is that the connectors CN02 and CN04 have the 12VDC and 24 VDC pins which are measuring below the values printed on the circuit card. The 12VDC pins were measured at ~10.5VDC and the 24VDC pins were measured at ~22.5 VDC. Should the measured voltages at these pins be higher to the 12 and 24VDC values?

If so, is the DPS-247AP B power supply card the source of my problem ?

By the way, I did not see any failed caps during my initial inspection of the board. But I did find a possible burnt lead from one of the high power side transformers.

[budm]

Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

@DFH, measure the DC voltage on the legs of that largest caps on the board, it should be rated at 350~450vdc on it, be careful not to touch anything with your hands, body, you will be working on the Line side of the power supply!
Lethal voltage.
Suggestion: you may want to start a new thread instead, this thread is getting too long and it is hard to keep track.

[DFH]

Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

Thanks budm, I will need to check tonight after work. I will be very careful not to touch any part of the board when measuring. I will set-up the meter, then power up the TV to measure, record, then power down. Lethal voltage is understood.

[budm]

Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

You can plug the TV in the GFI outlet just to be safe.

[DFH]

Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

Hello again budm,

Here is the meter reads for the 450V, 150 uF capacitor on the power supply card:

With the TV power switch off, the positive side reads 90.8VDC relative to the case ground wire and the negative side reads -49 VDC.

With the TV power switch ON, the positive side reads 317VDC relative to the case ground wire and the negative side reads -48VDC.

Also, when the power switch is selected to ON, the PSON signal reads 2.85VDC which is lower than I expected.

[budm]

Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

I am sorry, when you measure the voltage of that cap, you measure it directly on the two legs of the cap, not using the chassis as the ground point since we are working on the line side, the cold side you can use the chassis a the ground reference. The 2.85VDC PS_ON is high enough to turn the transistor on, so that is OK. So please take reading again for me.
By the way, does this model has two inverter board (left and right)?
Does your version look like this?
http://s807.photobucket.com/albums/y...37L%20HDTV10A/
By the way, try disconnecting the 24vdc connector from the power supply board, this connector goes to the inverter boards, we just want to find out if the Inverters are loading down the power supply due to shorts circuits, see if the TV will stay on this time.

[DFH]

Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

OK, I am back. Here are the new meter reading for the line side 450V cap:

TV switch Off, cap voltage between the two legs is 334VDC.
TV switch On, cap voltage between the two legs is 368VDC.

The TV model I have is VX37L HDTV10A and it has an inverter board on each side, just like your photos. I removed the left side (looking at the back) inverter 24VDC connector from the power supply board and selected the TV switch to ON and the backlight does not come on but the vizio logo stays on illuminated white. I then reconnected the left side and removed the right side inverter 24VDC connector from the power supply board, selected the TV switch to ON and had the same negative results. I noticed a small blue LED on the left inverter card did illuminate briefly, then went out.

I will start looking at the smd fuse and other components on the inverter boards for any signs of failure or damage.

I look forward to your continued help.

[budm]

Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

So when you disconnect the backlights inverters, the logo stays white? Am I correct? If that is the case, then it did not go into shutdown (logo turns yellow). it sounds like the problem is on the inverter board, it may have bad caps, bad MOSFETs.

[cashkennedy]

Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

I'm just curious, but is it normal for a tv in US to be seeing >340 volts on the big cap? Usually i only get 156 or so, which i thought was the logical DC conversion of 110ac. Maybe hes testing a 220v tv, but that seems odd considering hes in los angeles.

Edit: 110/220 combo designs might step up the ac before the bridge rectifier? that way no matter what the input it will still have the same DC voltage going into the transformer?

[budm]

Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

The voltage is step up by the PFC Voltage booster circuits, that is why you see up to 400vdc on that caps, very common design these day to use PFC circuits to raise efficiency (power factor as close to 1).

[DFH]

Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

Sorry for the delay, kids distracting me. Yes,I am using a 110/120VAC power outlet.

Yes, with the inverter connector disconnected from the power supply board, the logo does remain white and does not revert to orange. The backlight does not come on or even flash.

With both inverters connectors connected to the power supply board and the tv selected to ON, the backlight flashes briefly then goes out. But the Vizio logo now stays white and does not go to orange.

I checked the SM fuses on both inverter boards and looked for blown cap with negative results.

Any other checks?

[budm]

Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

DFH, I just hook up my power supply, when is is off I get 168vdc and 395vdc when it is on. Not sure if your power supply is the same as mine.