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Old 09-16-2019, 03:42 PM   #1
jason123
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Default Dell U3011 - Troubleshooting the Power Supply board PS-2201-3-HF

Hi folks,
I see many having issues with the U3011 monitor display (Westinghouse guts?)

I have one that would work if I unplug power from wall every once in a while. Was like that for about 3 months - Now, it doesn't turn on at all (front LEDs), but no backlight or other signs of life.

I replaced the Power Supply PS-2201-3-HF board and that took care of the problem.

I'm trying to repair the PS-2201-3-HF board. It has 2 connectors sets (top and bottom)
Bottom set seems to be just 24V and GND with ENA, ADJ, and HDCR

Top Connector, P802, is identical, but P803 has 5, GND, 24_EN

I buttoned up the Monitor so I'm troubleshooting this board on my workbench. To turn all the supplies on, I'm assuming I tie 24_EN to 5V (with a small resistor)?

Do I have to do anything with the ENA and HDCR pins??

Any common failures that anyone can share on this board?
Thanks
Attached Images
File Type: jpg 20190916_143735.jpg (612.9 KB, 11 views)
File Type: jpg 20190916_143748.jpg (864.7 KB, 11 views)
File Type: jpg 20190916_143808.jpg (756.3 KB, 9 views)
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Old 09-17-2019, 08:17 AM   #2
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Default Re: Dell U3011 - Troubleshooting the Power Supply board PS-2201-3-HF

Looks like 24_EN on P803 is not connected to anything. So I'm guessing the 24 V comes on when the "ENA" is tied high.. So I shorted it to +5V (which does come on), but the 24 V never comes up. Voltage across large Cap doesn't change - 164 V DC. Is this a PFC circuit issue? Looks like this uses the Fairchild FAN7529B. Schematic anyone?
Thanks
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File Type: jpg 20190917_080614.jpg (664.1 KB, 10 views)

Last edited by jason123; 09-17-2019 at 09:40 AM..
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Old 09-17-2019, 01:30 PM   #3
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Default Re: Dell U3011 - Troubleshooting the Power Supply board PS-2201-3-HF

Ok, update (to myself ) ENA is simply pass through - maybe to turn on the inverter power? I tied 24_EN to 5V, and now the PFC is working and voltage on large cap is 384 VDC. However the 24 V only comes up to 5.2 V.. and gradually drops to 3 and continues to drop. Does the 24V require a load on it?
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Old 09-18-2019, 08:04 AM   #4
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Default Re: Dell U3011 - Troubleshooting the Power Supply board PS-2201-3-HF

I'm not seeing a controller between the 5V to the 24V. Simply a transformer, some diodes and resistors and caps. Is that possible? are they modulating the 5V and transformer turn ratio sufficient to generate 24V then filter? is that it?
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Old 09-18-2019, 10:02 AM   #5
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Default Re: Dell U3011 - Troubleshooting the Power Supply board PS-2201-3-HF

Did you check that white fuse in your picture? close to R107.

Last edited by captainKKK; 09-18-2019 at 10:04 AM..
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Old 09-18-2019, 03:17 PM   #6
jason123
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Default Re: Dell U3011 - Troubleshooting the Power Supply board PS-2201-3-HF

That is labeled C107 - I know it's a bad photo. I didn't.. I will shortly and let you know. Seems that the PFC circuit is working - Large Cap voltage goes from 164 to 384 VDC.
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Old 09-19-2019, 10:19 AM   #7
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Default Re: Dell U3011 - Troubleshooting the Power Supply board PS-2201-3-HF

Cap C107 checks out.
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Old 09-19-2019, 08:17 PM   #8
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Default Re: Dell U3011 - Troubleshooting the Power Supply board PS-2201-3-HF

What are the voltages on P802 and 803 when it's turned on?
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Old 09-20-2019, 06:47 AM   #9
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Default Re: Dell U3011 - Troubleshooting the Power Supply board PS-2201-3-HF

Hi captainKKK... I found a couple of bad solder joints (actually arching as I move the board) so touched those up, and now 24V comes up to 24.67 V.. However, there is a chatter or relay sound (though I can't find a relay on the whole board)- Audio recording attached.. Seems shorting 5 V to 24_EN is too strong. When I use larger resistors the chatter goes away, but the rail only reaches 20 or 21 V. Any idea what resistance I should put between 5 and 24_EN?
Thanks
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Old 10-09-2019, 05:56 AM   #10
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Default Re: Dell U3011 - Troubleshooting the Power Supply board PS-2201-3-HF

Any help here is appreciated folks.. I'm still having the "Clicking noise" coming out of the transformer??? I replaced the parallel Cap on the primary, and that didn't fix the issue. I'm thinking maybe internal arching? However I can't find a replacement transformer. Can anyone confirm that this indeed could be coming from transformer?
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