Dynex DX-LCD32, with no power

[budm]

Oh, did you check the voltage on that big cap, will give us a clue toknow if the PFC Voltage boosting circuits are working or not since the 24vdc PS needs that section to work.

[wfdbackdraft]

Big cap is 168 vdc in standby, and 392 vdc with the tv on. And with the 24v cable disconnected from the inverter board, I'm still not getting any voltage on any of the wires.

[budm]

That is good that the PFC is working. Now we need to find out if the PS_ON is used to turn on the PFC which will in turn, turn on the 24vdc switching supply circuits. So I need to know which pin on the PS board is the PS_ON incoming signal, that is why I hope the connector will have some kind of labels on them.

[budm]

Oh I just re-read your comment again "I'm still not getting any voltage on any of the wires" Which wires, the 24vdc wires?

[wfdbackdraft]

Yes, no power to the the 24 vdc wires.

[wfdbackdraft]

Dynex 001.jpgIMG_20120302_185718.jpgIMG_20120302_185822.jpg

[budm]

Any luck on the labelling of the connectors, I will also need REALY GOOD CLEAR pictures of the back side of the power board, closed up pictures of the connector on the bottom side so I can try to trace out the connections. I have a feeling that the PS_ON signal is OK otherwise the PFC Voltage will not go up, and I thinnk the switching in the 24vdc is not working right now.

[wfdbackdraft]

I've discovered that my nice 14mp Nikon isn't focusing worth a damn, and my android phone is a lot better. Stand by while I pull the psb and get you a picture of the backside. The 24vdc connector does have some labeling. On/ Off, Dim, and GND.

[budm]

OK, most cameras have the MACRO function for closed up, most NIKON can focus as close 2~3" from the object.
By the way, the ON/OFF is for backlight On/off, the DIM is for lamps dimming control. Do you have 3.3~5DVC on the ON/OFF pin?
These two signals are generated in the main board and it is fed into the top connector of the power supply and go right through the connector to goes to the inverter board.

[wfdbackdraft]

The on/off has 2.75 vdc in the on position.

And I had to replace my camera's LCD screen. Takes pictures just fine, but even in Macro mode, it isn't focusing. I've been working with my phone to get some better pictures. Uploading in a minute, after I label them.

[wfdbackdraft]

IMG_20120302_192227.jpg

IMG_20120302_201618.jpg

IMG_20120302_201630.jpg

IMG_20120302_201639.jpg

IMG_20120302_201646.jpg

IMG_20120302_201654.jpg



Top - Serial Number of the board
2nd picture is the whole board. 12vdc connector is up in the top right, 24 vdc is in the bottom right.
3rd picture - top left
4th picture - top right - 12 vdc connector
5th picture - bottom right - 24vdc connector
6th picture - bottom left

I tried to open them in adobe to label, and it wouldn't open them. They are JPEGS. Not sure what they need to be for Adobe to open and edit.

[budm]

OK, I will look at the pictures to see what I can do for you, mean while if you want, you can read the basic guide on how LCD TV's and monitors work so you will understand why I ask for all these information. I hope you will get some basic ideas.

[wfdbackdraft]

Thanks. I will.

[budm]

OK, I look at the pictures, not too bad, I think they may be good enough for now.
Please see the PDF. I would like you to check the resistor as shown in the PDF, it should shows low Ohms, may be 10 Ohms or so, if it does read OK, then put the board back in but do not plug it into the outlet yet, heat up that area where the small cap is shown with hair dryer for about 3 minutes then plug the TV in and then try turning the TV on to see if the backlights will come on.

[wfdbackdraft]

OK BUD, I finally have a day off that I can look at things again. In your last post, you told me to "see the PDF", but I'm thinking that you meany to attach one with the resistor circled. If so, can you show me which resistor to heat up, and I'll let you know how it goes.

[budm]

Hmm, I do not know what happen to the attached PDF on the small cap Iwant you to heat up. So here is the PDF. I will also ahve to think back about the resistor I was talking about, trying to remember it.

[budm]

OK, now I remember the resistor I want you to Ohm out, this resistor (R939) is part of the power supply of the 24v SMPS circuits.

[wfdbackdraft]

I just Ohm'ed the R939 and the meter reads 0.00. (That is with the board disconnected, and no power, correct?) I tried the one above it, and I was getting a reading of about 27 to 29 ohms.
So should I still heat up that cap, or is this resistor not working right?

[budm]

Heat up the or replace the cap, the resistor seems to be OK, the resistor is connected one of the transformer widing to the Diode which will feed the DC to the SMPS IC once the switching circuits started.

[wfdbackdraft]

I heated the cap up really good with a hair dryer, and nothing happened when I turned it on.