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Old 11-02-2013, 08:30 AM   #7
kalmara
New Member
 
Join Date: Oct 2013
City & State: Vratza
My Country: Bulgaria
Line Voltage: 240VAC 50Hz
I'm a: Hobbyist Tech
Posts: 3
Default Re: Dell 2007FPB teardown

Hello, friends electronics & electricians.
I have recently aquired a Dell 2007FPB monitor and it's in near mint condition, but sadly - not functioning.
I work in the electronics area and I'm aware of the Ohm's law and etc., but it's difficult to repair the monitor without a service manual, even worse - without a single schematic. The pics and info in this thread have been very useful and I made a couple of conclusions but need help in order to continue with the repair.
My questions are mainly to the thread starter, budm, seems like you are a lot into this stuff, so hope you can help.

Things done so far :
Tested mains supply - 19VDC is OK.
USB/Buck converter board - blown 3amp fuse (F19), all the schottky's and fets tested OK, so I powered the board like so :

The result - 5V are OK, but 3.3V and 12V are gone. After I saw the 3.3V are gone I looked at the post of the fellow above me and found out that my ZD701 has also gone short and by the looks of it - seems like some sort of feedback to the TL1451 PWM driver IC, presumably 3.3V zener?? (not sure) I tried to desolder it to see if the 3.3V will pop up, but it broke apart as soon as I touched one of it's leads with the soldering iron. Another test - still no 3.3V and 12V, then I decided to check the gates of the mosfets and sadly they both have +VCC on their gates (19VDC) - the totem pole driver transistors tested OK, so I suspect the death of one of the PWM driver IC's (they are dual, so one is used fully, and the other is used 50%, coz only 3 voltages are needed).
Moving on to the main CPU board - the 3.3V rail measures a dead short to GND. I thought it was one of the linear regulators, so I desoldered one of them and the input pin of the other one, like so :

But sadly enough again - no change. There are a lot of caps to be suspected, especially electrolityc, but my main concirn is how to check if the graphical CPU os okay or not, because it would be a big FAIL if it hase gone bad and started up the whole butterfly effect.

The man from whom I bought the monitor told me it has worked flawlessly for 5 (five) years, and one day suddenly had an intermittent power issue - started turning on and off by itself, and then died just like that. All in the matter of 2-3 minutes.

p.s. Sorry if I have mistakes in the text - my mother's language is Bulgarian, not English.

Cheers!
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