Dynex DX-LCD32-09 Sound but no Picture

[gorr35]

So I picked up yet another freebie today (Dynex DX-LCD32) blue power light comes on, I get sound but no picture, I see nothing using the flashlight trick. No swollen caps, checked the voltages on all 3 connectors as shown on the first picture...from left to right:

1. 5.0v
2. 0.00
3. 0.00

Now what? Did I do something wrong?

[Dgtech]

Re: Dynex DX-LCD32-09 Sound but no Picture

I suspect the inverter alone is the problem. Usually that's at least the starting point for me. Check the voltages going to the inverter. Check the fuse on the inverter board - usually near the connector. Visually check the transforers on the inverter and check their primary/secondary resistances (with power off of course). All of these transformers should be somewhat close in comparison. Check the mosfets for resistances as well.

[gorr35]

Re: Dynex DX-LCD32-09 Sound but no Picture

So I tested the power supply again and here's what I got on the first connector on the left as pictured above:

32v = Travels from 31.6 - 32.2v
9v = 0
5v = 0
16v = 0
5v (next to PON)= 5.1v

The other two 24v connectors are reading 24.2v
What next?

[tom66]

Re: Dynex DX-LCD32-09 Sound but no Picture

Is there any writing next to the inverter connector (which goes to the PSU) which might indicate what pins do what?

[gorr35]

Re: Dynex DX-LCD32-09 Sound but no Picture

Is there any writing next to the inverter connector (which goes to the PSU) which might indicate what pins do what?

None at all....looked all over the net for a service manual/schematics, no luck.

[tom66]

Re: Dynex DX-LCD32-09 Sound but no Picture

None at all....looked all over the net for a service manual/schematics, no luck.

Hmm. Can you post a close up shot of both the top and bottom of the inverter where the connector fits on the board - clear and focused. It's usually easy to see the power and ground connections... not so easy for the ON/OFF, DIM, ERROR etc. pins which go to various parts of the board.

[gorr35]

Re: Dynex DX-LCD32-09 Sound but no Picture

Hmm. Can you post a close up shot of both the top and bottom of the inverter where the connector fits on the board - clear and focused. It's usually easy to see the power and ground connections... not so easy for the ON/OFF, DIM, ERROR etc. pins which go to various parts of the board.

Sorry but this was the best I could do for now as the battery on my camera went dead just as I was snapping pictures. In case you're wondering there is nothing printed behind the connector....and as you can see, there is no bottom side to the inverter board....everything looks to be surface mounted.

[tom66]

Re: Dynex DX-LCD32-09 Sound but no Picture

I can quite clearly see text next to the connector which says "GND" and "VIN", as well as others, although I can't read them well.

There are two fuses, the white objects right next to the connector.

Using your multimeter, test the fuses for continuity.

Set your meter to the 200 ohm range. Touch the leads together, and record the measurement, it will be around 1 ohm. Then, touch the leads to each fuse; record the value, and subtract the previously measured lead resistance, and post your results. You should get fuse resistances of less than 2 ohms, otherwise they have failed and need to be replaced, after determining why they have failed. (DO NOT bridge the fuses with wire - you must first find out why they have blown, if they have blown.)

Also, check the voltage going to the inverter pins. Test the voltage on each fuse, on the end closest to the connector. Place negative lead on some metal part of the case. Place positive lead on each fuse positive. Record and post results.

[gorr35]

Re: Dynex DX-LCD32-09 Sound but no Picture

I tested the fuses and got .09 on both. As far as testing voltages on the inverter.....stupid question here, the mainboard covers up the inverter board when put back together....how can I test the voltages without screwing the mainboard back in place and without causing a short?

[tom66]

Re: Dynex DX-LCD32-09 Sound but no Picture

I tested the fuses and got .09 on both. As far as testing voltages on the inverter.....stupid question here, the mainboard covers up the inverter board when put back together....how can I test the voltages without screwing the mainboard back in place and without causing a short?

Test the voltages on the PSU board, which is connected to the inverter.

[gorr35]

Re: Dynex DX-LCD32-09 Sound but no Picture

24.2v

[tom66]

Re: Dynex DX-LCD32-09 Sound but no Picture

24.2v

Sounds good.

Check the other pins: error, dim, etc. You may have to check them on the main board. Connect black to case of TV, red to each pin, (be careful not to short anything.)

[gorr35]

Re: Dynex DX-LCD32-09 Sound but no Picture

Sounds good.

Check the other pins: error, dim, etc. You may have to check them on the main board. Connect black to case of TV, red to each pin, (be careful not to short anything.)

I cannot check them on the main board....the connector that says ERR,DIM,etc. is on the inverter board and the other end of that cable goe's to the power supply that you had me check....24.2v. The connector on the power supply that supplies power to the mainboard is where I was having trouble.

32v = traveling between 31.6 and 32.2v
9v = 0
5v = 0
16v= 0
5v next to Pon=5.1

[tom66]

Re: Dynex DX-LCD32-09 Sound but no Picture

I cannot check them on the main board....the connector that says ERR,DIM,etc. is on the inverter board and the other end of that cable goe's to the power supply that you had me check....24.2v. The connector on the power supply that supplies power to the mainboard is where I was having trouble.

32v = traveling between 31.6 and 32.2v
9v = 0
5v = 0
16v= 0
5v next to Pon=5.1

Don't the connectors on the inverter board go to the PSU? Measure the corresponding pins. I might be missing something here, so let me know if I'm being stupid.

[gorr35]

Re: Dynex DX-LCD32-09 Sound but no Picture

Maybe i'm the one missing something....if you go back to the top of page (First Post) and open the first picture on the left, you'll see 3 sets of connectors on the power supply....the one on the far right is the one going to the inverter board....that's the one that tested 24.2v

[tom66]

Re: Dynex DX-LCD32-09 Sound but no Picture

Maybe i'm the one missing something....if you go back to the top of page (First Post) and open the first picture on the left, you'll see 3 sets of connectors on the power supply....the one on the far right is the one going to the inverter board....that's the one that tested 24.2v

Can you post an overall shot of your TV? I need to see the layout.

The DIM, ON/OFF etc. wires must go somewhere, so try and trace them; do they go straight to the main board, or to the PSU, or to somewhere else entirely? (In one case, I had the wires going to the Tcon... which is odd, to say the least.)

[gorr35]

Re: Dynex DX-LCD32-09 Sound but no Picture

Can you post an overall shot of your TV? I need to see the layout.

The DIM, ON/OFF etc. wires must go somewhere, so try and trace them; do they go straight to the main board, or to the PSU, or to somewhere else entirely? (In one case, I had the wires going to the Tcon... which is odd, to say the least.)

I think i'm the one confusing you! The first pic is the overall shot - the second pic is with the mainboard lifted up so you can see the cable going from the psu to the inverter. You had it right.....the connector with DIM, ON/OFF is the one on the inverter board end.....the other end goes to the 24v power supply connector. I'm assuming i'm not doing a very good job explaining myself.....or maybe i'm not understanding what you're asking me? I was forced out of bed 3 hours earlier than usual and i'm tired! LOL

[tom66]

Re: Dynex DX-LCD32-09 Sound but no Picture

I think i'm the one confusing you! The first pic is the overall shot - the second pic is with the mainboard lifted up so you can see the cable going from the psu to the inverter. You had it right.....the connector with DIM, ON/OFF is the one on the inverter board end.....the other end goes to the 24v power supply connector. I'm assuming i'm not doing a very good job explaining myself.....or maybe i'm not understanding what you're asking me? I was forced out of bed 3 hours earlier than usual and i'm tired! LOL

Yes, the wire goes from the inverter and goes to the PSU. It should be possible to trace each one and find out where they go to the PSU connector. It's also possible the cable will split, and some will go to the main board. Either way we need to see if the inverter is actually being told to come on (the main board here being a problem if it is not), or if the inverter itself is faulty (or if the CCFL tubes are faulty.)

[gorr35]

Re: Dynex DX-LCD32-09 Sound but no Picture

That's why I was wondering if it's the mainboard considering i'm not getting a reading from some of the pins going from the psu to the mainboard as follows:
32v = 31.6 - 32.2 (Keeps jumping up & down)
9v = 0 (Nothing)
5v = 0 (Nothing)
16v = 0 (Nothing)
5v next to PON = 5.1v

Edit: Think I got that backwards....it's the connector on the power supply going to the mainboard that's not getting the good reading, so would it be a psu problem not feeding power to the mainboard? The problem i'm having with that is that i'm still getting audio from the mainboard.

[tom66]

Re: Dynex DX-LCD32-09 Sound but no Picture

That's why I was wondering if it's the mainboard considering i'm not getting a reading from some of the pins going from the psu to the mainboard as follows:
32v = 31.6 - 32.2 (Keeps jumping up & down)
9v = 0 (Nothing)
5v = 0 (Nothing)
16v = 0 (Nothing)
5v next to PON = 5.1v

Edit: Think I got that backwards....it's the connector on the power supply going to the mainboard that's not getting the good reading, so would it be a psu problem not feeding power to the mainboard? The problem i'm having with that is that i'm still getting audio from the mainboard.

*Usually* with audio, the power supply is okay. For now, leave it alone, as you have no backlight, right? That's the first problem.

This is confusing. What cables go from the inverter to other boards? Post a CLEAR picture of the connector on the inverter side, clear enough to see the labels next to the pins.