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Old 10-02-2018, 09:46 PM   #21
budm
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Default Re: Dell U2713Hb No Display

So that regulator is 12V regulator, and more likely to be LDO type which will usually require about 2V differential Voltage between Input and Ouputt to properly regulate the output Voltage, so what is the input Voltage feeding the regulator pin?
'That was all tested with the timing controller board disconnected'
That switched MOSFET will not have any load connected to it if the LVDS cables are not connected so it should barely drawing any current, you should check the resistance. against GND on the output side of that MOSFET.
It may have bad MLCC (Multi Layer Ceramic Capacitor) on the output side of the MOSFET.
You can see the output pins of the switched MOSFET are connected to the Lytics cap, then is fed to two inductors (L18, L??), and two bleeder resistors to GND, and MLCC filter cap C815 and then the power pin of the LVDS conector.
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Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956

Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999

Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl

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http://s807.photobucket.com/user/budm/library/

TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809

Last edited by budm; 10-02-2018 at 09:53 PM..
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Old 10-06-2018, 07:47 AM   #22
drjaydenm
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Default Re: Dell U2713Hb No Display

Thanks for explaining that part of the circuit, it makes sense now. It turns out I was turning on the wrong gate which caused the ground gate to open too No wonder it was shorting... lucky I didn't wreck anything!

As I can't see any other problems with components at this stage, I've hooked up to the debug UART serial port and got the following logs out on startup from the STDP9320-BB chip.

Quote:
Dual Flash Bank is disabled..!.
Init PCTL. April 27 2012.<.
DDR3 - W631GG6KB-15.
PCTL32_PUB_SMCTL check fail...
PCTL32_PUB_SMCTL_lo = 0x%x....
PCTL32_PUB_SMCTL_hi = 0x%x.˝,
IFM measured RC-OSC Clock Value = 0x%x.◊.'
Calibrated RC-OSC Trim Value = %d...8%
Measured RC-OSC Clock = %d000Hz.We.
Uploaded LPM: %d bytes.W.
OtpSramInit OK..
LPM DC off!.
The line
Quote:
PCTL32_PUB_SMCTL check fail...
looks interesting to me, although I have no idea what it means...

Budm, do you have any clue on this one?
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Old 11-16-2018, 04:19 PM   #23
drjaydenm
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Default Re: Dell U2713Hb No Display

So I managed to get the monitor up and going and everything seems to work now.

I spent hours and hours probing that logic board, but couldn't find what was wrong with it - I also couldn't work out what the codes in the logs posted above mean, they could have been the key I feel.

I ended up buying a new logic board for $45 USD and it fixed the issue! I felt it was worth it as an equivalent monitor is still worth a few hundred dollars. This was a great learning project where I've leant a lot, but the problem was above my experience level.

Thanks for all your help budm, you really helped me in isolating the issue and boosting my understanding of circuits!
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Old 04-29-2020, 07:05 PM   #24
alittlelewd
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Default Re: Dell U2713Hb No Display

Sorry to necro this thread, but I believe I have the same problem as both you and the other guy from Poland from this thread - https://www.badcaps.net/forum/showthread.php?t=63998

I too have that fet blown, possibly taking the trace with it. The fet? that you said got very warm completely blew on my 2713h logic board, releasing a lot of magic smoke and possibly damaging other components.

Image below:


I have tried ordering the replacement logic board from TaoBao (the only site on the internet I can find who has this advertised), but after 3 weeks it hasn't shipped and I don't think it will ever come.

I would like to try and replace both the fet and the IC next to it as a possible fix, but reading through the very few topics online about it, I can't actually find a replacement for either the fet or the IC.

Does anyone know what those parts actually are? Or does anyone know where I could find purchase a replacement logic board?
Attached Images
File Type: jpg AyYIXla.jpg (777.4 KB, 5 views)

Last edited by Per Hansson; 04-30-2020 at 03:31 AM.. Reason: Offsite image uploaded
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Old 07-04-2020, 05:58 AM   #25
gregac
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Default Re: Dell U2713Hb No Display

Hi,

I'm having very similar symptoms as drjaydenm.

At first I was able to power on the monitor - "waterfall" animation started, but screen stayed black. After few tries, power button stoped reacting. If I touch "touch buttons", all lit up and can only be turned of by pulling out power cord.

What I have checked:
- Power Board and panel is ok - I pulled logic board from another working monitor and everything is working fine.

I found short over few caps behind processor and memory. But I couldn't find yet from where this short is coming. I tried with "freeze spray" but still nothing stands out.

What I noticed is that after I connect power cable, I can hear very slight 'click'.
If I leave it turned on like this, I can feel that heatsink on processor is warm.
The same is true on another working monitor.

I'm wondering if maybe processor / memory could have short?

Any other idea what could be causing that "shorts"?

Later Today I will post few photos where this shorts are ...

Regards,
Gregor
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