Vizeo E370VP no 12vdc

[maxnukem]

Hey all, I have a 37" set that will not turn on. When the power switch is pressed, the power board has a bit of a buzz (need to go someplace quieter or I need better ears to figure out which specific componnent is making the noise) but no backlight, video, or sound comes up.

Measurements I've already taken: (DC values across cap legs and secondary side voltages from chassis ground)

- 114 vac into power board.

before pressing power button:
- 160 vdc on each of the large primary side caps (C800A/B)
- primary side C907 comes up to about 22-24 vdc when plugging in set then settles at 14vdc a few seconds later
- secondary side pair of caps C950A/B each read 5.22 vdc
- 12 pin connecter to main (CN202) has 5.1 vdc on pins 1-3

- pin 11 reads 0 until power button is pressed then reads 3.2vdc until the power button pressed again and drops back to 0
- the other pins all read 0, even after pressing power button. There are a couple of grounds that I obviously expect to read 0vdc but the 12vdc pins to the main board and the DIM & BL_ON signals never change

-whlie the 3.2 vdc is applied to power board, the big pair of primary side caps reads 395 DC each.

-I got 0 vdc acoss secondary side caps C700A and C704 regardless of power on signal applied to power board.


Looks like I have STBY power and power on signal back to power board from main board when button is pressed but then the 12VDC to main board never comes up and the LEDs never turn on either. I just finished reading one of the threads about VIZIO voltage regulators so i found some other post about how they work and how to measure them. I'm going to go back, look up datasheets and take some more values across any voltage regulators I can find.

I'll get back with more readings but if anyone has any other suggestions or wants to look at something specific, please let me know what else to check next. I did throw a picture of the main board in as well but I really don't think I have any issues there and I need to learn how to take pictures under better lighting or something to get rid of the glare.

Thanks!

[budm]

Re: Vizeo E370VP no 12vdc

Can you re-take the pictures of the whole power supply board top and bottom? Your pictures are cutoff but has better resolution than the one from shopjimmy.

[budm]

Re: Vizeo E370VP no 12vdc

'I obviously expect to read 0vdc but the 12vdc pins to the main board and the DIM & BL_ON signals never change' so the DIM and the BL-ON stay at 0VDC and the meter did not show even a pulse?

[budm]

Re: Vizeo E370VP no 12vdc

Look at the traces of the board, Transformer T901 (driven by Power MOSFET Q901) is used for producing the 5VSTBY (Diodes D950A, B) and the switched 12V (D120A, and switched Power MOSFET Q120 which is turned on by PS-ON signal).
So you need to take the DCV readings of all 3 pins of Q120 with ref to the chassis GND so I can see if it is working or not.

[maxnukem]

Re: Vizeo E370VP no 12vdc

so the DIM and the BL-ON stay at 0VDC and the meter did not show even a pulse?

I did not monitor those signals while pressing the power button. I did that "assume" thing and figured without 12vdc to the main board, they would not change during power up. I'll make sure to check them next time while I try to power up the set.

I did take several measurements on what I assume to be voltage regulators. I haven't found datasheets for the chips yet but I'm including the data printed on the IC along with my measurements. With no datasheet, all pins are numbered from left to right across the bottom of the chip. I have also added a couple more overall shots of the power board.

readings listed while set in standby and then while 3.2 vdc power on signal

-Q901
k3566
pin1= 0 0
pin2= 160 388
pin3= 0 0.1

-Q600
k3565
pin1= 0 12.4
pin2= 0 0
pin3= 0 0

-Q800
k12A60U
pin1= 0 1.9
pin2= 160 24
pin3= 0 0

-Q120
40P03GI
A34020
pin1= 22.5 22.6
pin2= 0.4 0.4
pin3= 22.5 22.6

-D120A
YG902C2
pin1= 5.2 3.4
pin2= 22.6 22.6
pin3= 5.2 3.4

-D950A and D950B are the same chip with identical readings
FCH10A10
A3A
pin1= 0 0
pin2= 5.22 5.22
pin3= 0 0

edit: update on cn202 values... is there a emoticon of a donkeys backside? cause i feel like one ...
pins 1-3 VSB = 5.2
pins 4-7 SGND
pins 8-10 board says 12.6 = 0.43 vdc then falls to 0.012 after power button pressed. back to .43 when power pressed again
pin 11 Remote ON_OFF = 0 then 3.2 when power button pressed and back to 0 when power pressed again
pin 12 BL_ON= 0 then 3.2 when power button pressed and back to 0 when power pressed again
pin 13 labeled as NC but there is a red wire between the boards
pin 14 DIM=0 then comes up to 3.2 for a few seconds after power pressed, falling to 2.7 shortly after. back to 0 when power pressed again

Don't you ever get tired of pointing out what must seem glaringly obvious to you Budm? Thank you so much for all the work you put into this forum. I have found your articles and guides very informative and helpful.

[budm]

Re: Vizeo E370VP no 12vdc

'-Q120
40P03GI
A34020
pin1 (G) = 22.5 22.6
pin2 (D) = 0.4 0.4
pin3 (S) = 22.5 22.6

So far the other signal Voltages did toggle but the 12V stays basically at 0V output.

This Q120 P-CH MOSFET is not being turned on, the Gate Voltage should be at least 3V less than the Source pin for it to be on. You will have to trace this Gate pin to see where it is connected and how it is being controlled, this will not be easy.

'-D120A
YG902C2
pin1= 5.2 3.4
pin2= 22.6 22.6
pin3= 5.2 3.4'

The reading on pin 1 and pin 3 are error due to you are trying to read high frequency AC feeding the Anode of this Common Cathode rectifier, but I am surprised that you are getting 22VDC for the 12V power supply taht is fed to switched MOSFET Q120..

[maxnukem]

Re: Vizeo E370VP no 12vdc

I'd like to find the datasheets for the either of the transformers so I can verify they are working. Especially T601 since it appears to power the section of the board I am getting a bunch of 0vdc readings. here is what is printed on the transformer:
MP-130I (00)
MV-DP10593 DELTA
DCUM1102(03)5D3

more measurements I took (mostly 0 vdc readings):

-D700
STTH9L06FP
GKOJS VU
pins 1&2: 0
-C700A: 0
-Q714
20N15GI
A05018
pin1: 0
pin2: 0
pin3: 0
-d703
FCH10A10
pin1: 0
pin2: 0
pin3: 0
-C704: 0
-I found no chip id on primary side component BD1. It has 4 pins, marked + ~ ~ - and maintains 160 vdc across +- when in stby and drops to 137vdc when power button pressed

It will be several days before I make time to get back into this TV. Hopefully I can turn up some more information on this specific board by then. I'm having more difficulty than I expected finding pinouts and datasheets for the board components than I was expecting. I'll also look up information about surface mount soldering. I've done plenty of through hole soldering but have never installed any surface mount components nor worked with any of the equipment required for reballing ICs.

[budm]

Re: Vizeo E370VP no 12vdc

T601 is for the LED backlights power supply, doubt that it is bad.
'and maintains 160 vdc across +- when in stby and drops to 137vdc when power button' That is bad if it is the case, it should go up close to 400VDC due to the PFC Voltage booster circuit is turned on when PS-ON is present. For it to drop to 137Vdc it means the filter caps are really bad. Something wrong in measurement some where or you have bad main filter caps.

[maxnukem]

Re: Vizeo E370VP no 12vdc

... For it to drop to 137Vdc it means the filter caps are really bad. Something wrong in measurement some where or you have bad main filter caps.

Finally back and had some time to look at this again today. Verified BD1 has 160vdc in stby and drops to 137vdc after pressing power button. The pair of large caps C800a/b measure 160 in stby but come up to 395 after power switch is pressed.

I also de-soldered and measured capacitance of C801. C802, and CX1, CX2, & CX3. all read within 5% of listed values. are those the filter caps you were talking about?

[budm]

Re: Vizeo E370VP no 12vdc

Finally back and had some time to look at this again today. Verified BD1 has 160vdc in stby and drops to 137vdc after pressing power button. The pair of large caps C800a/b measure 160 in stby but come up to 395 after power switch is pressed.

I also de-soldered and measured capacitance of C801. C802, and CX1, CX2, & CX3. all read within 5% of listed values. are those the filter caps you were talking about?

So when the power switch is activated the dcv on the filter cap goes up to 395VDC and stays there at 395vdc or it drops down to 137VDC?
At least we know that the PFC Voltage booster is working and able to boost the Voltage up.

[maxnukem]

Re: Vizeo E370VP no 12vdc

goes up to 395 and stays there.

On a positive note, the buzzing sound that happened when power was pressed turned one dropped significantly after i went ahead and changed out CX2 and CX3. Barely and audible hum now. Still no backlights or 12vdc to mainboard tho.

Trying to track the gate signal for Q120 is definitely a challenge and I'm working on that currently.

The positive leg of C120A/B is tied directly to the source for Q120 and to D120 though a ferrite bead.
Q120 gate and source are separated by a 10k resister and the gate is also tied up into the surface mount components through 10k R128B then to Q122 (marked with a PO at one end and t2X across it)
Is it likely that one of the numerous tiny surface mount ICs could be the culprit or do these type of problems generally stem from larger components?

[budm]

Re: Vizeo E370VP no 12vdc

OK, good now we do have PFC Voltage, so let me trace out the board to give you some test points on the board.

[maxnukem]

Re: Vizeo E370VP no 12vdc

I edited my previous post, if you need a zoomed in shot or better picture, please let me know