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Old 02-10-2012, 02:21 PM   #1
wfdbackdraft
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Default Dynex DX-LCD32, with no power

I'm new to this forum, and new to TV repair so bear with me. I've fixed a few with bad caps, but this one is more involved.

It's a Dynex DX-LCD32. It's not the one with the "-09" either. That one looks different inside. I picked this one up cheap because it doesn't power on. The guy did say that it would work every now and then, but I haven't seen it yet. I plug it in, and get the orange stand-by light. Press power and the light turns to a solid green. No picture or any sounds. To get it back to stand by mode, I have to press power twice, and get orange flashes. It's really quick, and I tried to count. I either got 9 flashes, or a few times it does abut 15, then stays a solid orange.
I've looked at every capacitor and none are bulging.
I have a digital multimeter, and am ready to check whatever that you tell me. Keep in mind that I have very little knowlege of electronics but am willing to learn. I've enclosed some photos of the boards.
Thanks for any help that you guys can give me. I'm not looking to get into the business, just trying to get a decent TV for the garage.
Michael
Attached Images
File Type: jpg Dynex 001.jpg (380.1 KB, 86 views)
File Type: jpg Dynex 012.jpg (349.0 KB, 68 views)
File Type: jpg Dynex 009.jpg (518.8 KB, 41 views)
File Type: jpg Dynex 010.jpg (280.0 KB, 35 views)
File Type: jpg Dynex 011.jpg (320.6 KB, 29 views)
File Type: jpg Dynex 005.jpg (440.7 KB, 30 views)
File Type: jpg Dynex 006.jpg (410.2 KB, 30 views)
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Old 02-10-2012, 02:59 PM   #2
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Default Re: Dynex DX-LCD32, with no power

Are there any markings on the cable going from the PSU to the main board?

If so, check the voltages on the pins match these markings.

I notice one Rubycon cap and a few Chemicons - did you replace these or did someone else? (Or are they factory originals?? That would be very surprising...)
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Last edited by tom66; 02-10-2012 at 03:04 PM..
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Old 02-10-2012, 03:50 PM   #3
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Default Re: Dynex DX-LCD32, with no power

I did check those voltages on that side of the PSU, and here is what I got:

Red and Orange both have 13.2v, and were marked 12v on the board. Yellow and Green both have 5.1v and are marked as 5v on the board. The only other marking was what looked like 1 15v. Not sure if that was supposed to be 1v and 15 v, or what. But neither wire had anything. These wires are going to that small rectangle board. There were 3 wires with no markings on the board but had current. White 2.7, Black 4.0, and Brown 3.1. These were going to the main board.
And all of these readings were with the green power light on.
I also checked the other output on the PSU and got nothing except .1 on the wire marked dim on the board.
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Old 02-10-2012, 03:51 PM   #4
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Default Re: Dynex DX-LCD32, with no power

And I haven't replaced anything, and as far as I know neither did the previous owner. He never mentioned it.
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Old 02-10-2012, 04:02 PM   #5
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Default Re: Dynex DX-LCD32, with no power

The 12V lines measured 13.2V? That's rather high... Something doesn't seem right. Where were you measuring ground?
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Old 02-10-2012, 04:10 PM   #6
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Default Re: Dynex DX-LCD32, with no power

At the chassis ground screw.
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Old 02-10-2012, 04:41 PM   #7
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Default Re: Dynex DX-LCD32, with no power

Quote:
Originally Posted by tom66 View Post
The 12V lines measured 13.2V? That's rather high...
From the computer lcd monitor world, a lot of the secondary voltages are unregulated and appear high, but then fall into "spec" when everything is working (i.e. there is a proper load).

It may be the same in the TV world especially since the backlights are not on to draw any load.
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Old 02-14-2012, 09:20 AM   #8
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Default Re: Dynex DX-LCD32, with no power

Anyone?
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Old 03-02-2012, 03:07 PM   #9
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Default Re: Dynex DX-LCD32, with no power

Still sitting here with an open TV. Can someone help me out please? I'm ready to get this thing fixed.

Thank you!
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Old 03-02-2012, 04:01 PM   #10
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Default Re: Dynex DX-LCD32, with no power

Can you please take good clear pictures of the the whole chassis so we may be we will be able to see how it is wired up? We also need to see the third connector on the power supply board which I think it goes to the Inverter board, back side pictures of the power supply, closed up pictures of the inverter multi-pin connector, LCD panel make, model, revision number so we can look up the spec of the LCD panel which will show the T-CON and inveter board pin out of the connectors, etc.
By the way, do you get sound?, also try turning it on without the inverter board discoonected from the power supply board.

Last edited by budm; 03-02-2012 at 04:12 PM..
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Old 03-02-2012, 04:03 PM   #11
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Default Re: Dynex DX-LCD32, with no power

Thanks Bud. I'll get working on those pictures and specs tonight when I get home. I appreciate the help.
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Old 03-02-2012, 04:25 PM   #12
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Default Re: Dynex DX-LCD32, with no power

Looking at your picture of the power supply, I think this is what it has on it, see PDF. Right now the standby PS seems to be working (this power supply is running 24/7).
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File Type: pdf PS TOP.pdf (295.4 KB, 66 views)
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Old 03-02-2012, 05:06 PM   #13
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Default Re: Dynex DX-LCD32, with no power

All of your assumptions are correct about where the wires are going. And I checked the voltage on the cap, and they fell right in line with where you said that it would.
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Old 03-02-2012, 05:08 PM   #14
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Default Re: Dynex DX-LCD32, with no power

So if I am right, right now you do not have the 24vdc feeding the Inverter board, yes/no? If not, disconnect the cable to the inverter board an see if the 24vdc comes back since if the 24vdc PS circuits sensing over current draw, it will go into shutdown mode.
Another reason you do have 23vdc can be due to 24vdc circuits itself, or it is not getting the command from the main board to turn it on.
Any voltage labels on the power supply connector at all? That will be a big help if they are labeled.

Last edited by budm; 03-02-2012 at 05:11 PM..
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Old 03-02-2012, 05:13 PM   #15
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Default Re: Dynex DX-LCD32, with no power

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.
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Old 03-02-2012, 05:25 PM   #16
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Default Re: Dynex DX-LCD32, with no power

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.
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Old 03-02-2012, 05:28 PM   #17
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Default Re: Dynex DX-LCD32, with no power

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.
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Old 03-02-2012, 05:34 PM   #18
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Default Re: Dynex DX-LCD32, with no power

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?
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Old 03-02-2012, 05:35 PM   #19
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Default Re: Dynex DX-LCD32, with no power

Yes, no power to the the 24 vdc wires.
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Old 03-02-2012, 05:40 PM   #20
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Default Re: Dynex DX-LCD32, with no power

Dynex 001.jpgIMG_20120302_185718.jpgIMG_20120302_185822.jpg

Last edited by wfdbackdraft; 03-02-2012 at 06:12 PM..
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