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Dell 1801fp flat panel monitor power supply problem

 
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xxjakextxx
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PostPosted: Thu Feb 12, 2009 7:07 pm    Post subject: Dell 1801fp flat panel monitor power supply problem Reply with quote

My dell monitor just died recently, no power.
I am a beginner at electronic repair hope if someone is an expert in this field could give me a few pointers, your help is greatly appreciated.

so here is what i have done so far.

i've opened it up and taken out the power supply/inverter board.

after a few testing it seems the 12V and the 5V from the power supply going to the logic/main board has a lot lower voltage than 12V and 5V. i think they were 2V and ~8V--> this lead me thinking that the problem is within the power supply board.

but thats all i know, all the electrolyte caps on the power supply looks normal and nothing looked burned.

can somone please point me to the next step on what to test in order to troubleshoot the problem??
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jts1957



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PostPosted: Thu Feb 12, 2009 9:10 pm    Post subject: Reply with quote

Do the 5 and 12 volts go up if power supply/inverter board is unplugged from logic/main?
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xxjakextxx
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PostPosted: Fri Feb 13, 2009 2:32 am    Post subject: Reply with quote

jts1957 wrote:
Do the 5 and 12 volts go up if power supply/inverter board is unplugged from logic/main?


no, i actually tested the power board with out connecting them to the mainboard and the voltage is below 5v and 12v.

i was thinking could it be the power fet, the switch mode power supply, or the secondary diodes, based on some research i did on google. but the thing is i have no idea to test any of these parts.

any suggestions?

thanks in advance
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jts1957



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PostPosted: Fri Feb 13, 2009 4:09 am    Post subject: Reply with quote

Does it use 2as01 as the regulator driver IC like in Dell 1800? I just got one fixed - Pin #6 to (hot) ground was 6 ohms.
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xxjakextxx
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PostPosted: Sat Feb 14, 2009 12:31 am    Post subject: Reply with quote

jts1957 wrote:
Does it use 2as01 as the regulator driver IC like in Dell 1800? I just got one fixed - Pin #6 to (hot) ground was 6 ohms.


it actually uses another type of IC.

I dont quite understand how to check the ICs but I measured the pin#8 and it has a voltage of 125 volts.
perhaps some pointers on testing the ICs? its 1200ap60 is the part number

thanks for your help
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jts1957



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PostPosted: Sat Feb 14, 2009 12:51 am    Post subject: Reply with quote

Here's datasheet:
http://pdf1.alldatasheet.com/datasheet-pdf/view/84615/ONSEMI/NCP1200AP60G.html
Pin #6 is B-plus (9 - 12 volts).
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xxjakextxx
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PostPosted: Tue Feb 17, 2009 8:19 am    Post subject: Reply with quote

hey jts1957,
i just tested pin #6 and the voltage measure is actually 12 volt- so i assume the ic is fine.

actually rested the 5 volt and 12 volt out with everything plugged in and everything seems to be fine, i get exact 5volt output and 12 volt output from the board-does that mean its not the power board thats causing the problem but perhaps the logic board?

I've also measure the other pins next to the 5 and 12 volt output-i believe these are input signals from the logic board. they are labeled N.C, dimming, ON/OFF, N.C. i couldn't get any voltage reading so that makes me think if the power board is actually fine but the logic board is shot and not transmitting any signals to fire up the inverter and the monitor?


any ideas on how to test the logic board or trouble shoot it?


again jts1957 thanks for your help

sincerely thank you!
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jts1957



Joined: 24 Nov 2008
Posts: 2472
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PostPosted: Tue Feb 17, 2009 4:15 pm    Post subject: Reply with quote

It does sound like power board is working.
If have access to second monitor - swap board.
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