Dell 2007FPB teardown

[Behemot]

I've replaced the mosfet with another 2SJ598 with no change. Tested all the 272 resistors and they seem to be very well in spec.

ADD// Eh, guys, did these displays came in pairs? I opened the other one and everything is mirrored in there. What was right is left and vice versa. The USB board has all four channels with four DC-DC modules.

[Behemot]

So the DTC for the +12V part of the TL1451 is at 2.44 V which means it is at 0 duty cycle. I think the problem is here.

I have checked all the corresponding SMD resistors and tiny SMD transistors around other TL1451s and all of the values are the same. So it seems those are OK. That really leaves me with bad TL1451 only?

Replaced TL1451 from scrapped display, no change! Bloody hell this PoS.

[Behemot]

[Bungz]

I just did the most grimy 2.7k fix, I should have taken pictures.

Used an enormous leaded resistor lol

Works perfect now

[Behemot]

Still have not found anything. All the resistors check fine and have same value as resistors in the same position of the second PWM controller which works fine providing both +3.3 and +5 V. But the +12 V is jsut still not there. Something is making the PWM go into 0 % switching mode.

[huge]

Behemot, it sounds like you need to start a new thread. If you have some time, you could start a FAQ on troubleshooting lack of one rail when the others are working.

[rdagger]

Loud crackle and smoke today. Serious scorch marks on the board by the outlet (see pics), but I don't see any other visual signs or bad caps. Anyone have any insight into which parts may be the culprit?

[budm]

You had bad solder joints on the AC inlet to the circuit board, clean off all the carbon deposit and resolder all 3 pins and inspect the board for bad solder joints.
Common problem.

[Behemot]

That's not safe to use any longer. I am afraid you will have to remove the inlet, clean as much as you can, drill out the burned stuff and solder IEC C14 cable in the two good positions and somewhere further on the single bad position (maybe on the fuse directly). Than somehow firm it in position so nobody tears it off.

Or you can cut piece of the board out and than place a new one in there with some epoxy, but that's too much of a work if you ask me and I am still not entirely sure it would be safe on full AC input voltage…

[stj]

buy a new connector - and sand away all the carbon on the board.

[Behemot]

It's burned too close to the ground, replacing won't fix that. Besides, there is almost nothing left from the copper pad, where would you like to solder it??

[rdagger]

Originally Posted by Behemot

It's burned too close to the ground, replacing won't fix that. Besides, there is almost nothing left from the copper pad, where would you like to solder it??

You're correct the solder pad is gone along with most of the outlet post.

[rdagger]

Thanks everyone for the advice. I found a new OEM power board on eBay for $25. Popped it in and my display is like new.

[Behemot]

Kinda expensive, new connector should cost like a buck and than it only needs some soldering and silicone tricks (or something similar)

BTW recently I've been disassembling the speakers I got which blew the +12 V rail. I think the reason is obvious…all caps were like 99 baloons. So next time before you connect those Dell speakers to your expensive display, always recap that thing first! You'll save yourself lot of troubles. And test them with external +12 V source lol

[budm]

Might as well resolder those 3 post so it will not fail like the original one, the AC inlet is not well mounted and supported so plugging and unplugging the power cord at the inlet will weaken the joints seen too many of them failed.

[johnz16]

Budm, you made a post #129 abought samsung capacitors for ln52a550 tv the capcitors look the same but have different part numbers so witch one goes on top and witch one goes on the bottom I CHECKED AND ONE IS 35-OHM AND THE OUTHER IS 70-OHM ??thanks,john

[lappen]

Hey guys,

i just fixed another 2007 WFP by replacing the 2,7 k resistor. Thx for the information. It was really hard to solder this little tiny resistor out and solder the new in... didnt really think it would work but it did.

[Radek]

Thank you all, Could not have done it without you
Yesterday afternoon and half a night was well spent. Ordered power supply from eBay for my 2007FPb 1200x1600 monitor, but that was a $40 bust. That was not it. Combing internet and
Finding Badcaps, measuring values on four boards components, I came across the defective resistor. Found 2.7K resistor in my parts supply and soldered it in. not the prettiest soldering job, but guess what it works.
Cheers,
Radek

[dseselectric]

I just wanted to thank all involved for this post.

I was after an old monitor to use on a CCTV system. Being a cheapskate (as I am), rather than buy one, I popped to my local waste & recycling centre and found one of these babies on the scrap pile. As it looked in good nick, I whipped it onto the van, but on getting it home found it wouldn't power up.

I popped her open to check internal fuses and PSU caps all to no avail, then I came across this thread. Sure enough, that 2.7k resistor was open circuit, but I found a suitable candidate on a scrap PIR sensor.

Seems funny that something so small should bring the whole thing to its knees. I assumed it would be a PSU fault and never imagined it would be a resistor hidden under a glob on the USB board.

Still, I'm an electrican by trade, not an electrical engineer, so 230v cables and nuisance tripping RCD's are my cup of tea. I doff my hat to you chaps though; you really know your bananas!

Cheers,
David.

[wdrummond]

I replaced the 272 resister but still now power button light. Has anyone found any other likely suspects for this monitor? Mine is the 2007wfpb. Thanks.