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UpThyWazzoo replied to EA261WM doesn't power on

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12-07-2013, 08:29 AM
Re: EA261WM doesn't power on

Thread resurrection!

I was never able to rectify the problem myself. However, I gave NEC a call to see if they could point me in the right direction and it turned out the monitor was still under warranty and they replaced it free of charge and shipping. Awesome customer service. I'm still using the same screen and probably will continue to do so until I decide to pick up one of those fancy schmancy 2560x1440 displays

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UpThyWazzoo replied to EA261WM doesn't power on

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09-02-2011, 12:50 PM
Re: EA261WM doesn't power on

I finally got the replacement ICs, and have tried two of them. I replaced the startup capacitor. There is still no output on Pin 6. Looking at the specsheet again, it says that the gate output will shut off should Vcomp be less than 1.4V. Since I'm getting around 1.42-1.45, could that be too low? How would I go about raising the voltage on that pin?

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UpThyWazzoo replied to EA261WM doesn't power on

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08-08-2011, 11:29 AM
Re: EA261WM doesn't power on

Okie dokes. I guess my next update will be when I receive the ICs. Apparently it'll take 2 and a half weeks to ship

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UpThyWazzoo replied to EA261WM doesn't power on

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08-08-2011, 10:00 AM
Re: EA261WM doesn't power on

Okay, I can do that. I was just curious because the resistor definitely absorbed too much current at some point--even the PCB right beneath the resistor was discolored a little bit. Tracing back from the resistor to the BJT at Q902, it looks like the collector is passing current through from the bridge rectifier at BD901 and inductor at L902 (once it gets the high signal from IC905, or from IC904). I assume it's an inductor because of the L, but I could be wrong. Could one of these components be doing something wrong? Or could a random voltage spike...

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UpThyWazzoo replied to EA261WM doesn't power on

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08-07-2011, 10:32 PM
Re: EA261WM doesn't power on

What wattage for the 20ohm replacement resistor would be recommended?

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UpThyWazzoo replied to EA261WM doesn't power on

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08-07-2011, 02:36 PM
Re: EA261WM doesn't power on

well, I removed the diode entirely. I guess I shouldn't be measuring this stuff in-circuit. It now measures infinity/8MOhm, and .57V on the diode tester. So I guess false alarm. I also removed the startup cap and it measured correctly (9.47 uF, 10.0 rated).

On the plus side, it looks like I can obtain 5 of the LD2257PS ICs for about 11 USD total, so I will do that now.

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UpThyWazzoo replied to EA261WM doesn't power on

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08-07-2011, 01:59 PM
Re: EA261WM doesn't power on

there are other diodes marked with "A2" on the board. Could they possibly be this: [url]http://jinghenggroup.en.alibaba.com/product/282163379-209761670/Surface_Mount_Glass_Passivated_Rectifier_Diode_A1_A7.html[/url] ?Re: EA261WM doesn't power on<br /> ...7.html[/url] ?Re: EA261WM doesn't power on

there are other

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UpThyWazzoo replied to EA261WM doesn't power on

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08-07-2011, 10:38 AM
Re: EA261WM doesn't power on

I believe D907 is shorted (21.9Ohm/21.9Ohm), but I can't ascertain its value--it says "A2" on the top. Also where is the "startup capacitor" ?

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Last edited by UpThyWazzoo; 08-07-2011, 12:06 PM.
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UpThyWazzoo replied to EA261WM doesn't power on

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08-06-2011, 11:04 PM
Re: EA261WM doesn't power on

I think I might have blown a fuse on my multimeter by trying to measure resistance while the power board was plugged in. Before that, however, I measured Vcc on IC 906 and it was 0. I'm not sure if that will be helpful at all, but I guess I'll update again when I get the multimeter to work.

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UpThyWazzoo replied to EA261WM doesn't power on

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08-06-2011, 09:31 PM
Re: EA261WM doesn't power on

I see. The block diagram also shows the current sensing pin being compared to .85V? Could my reading of 3.2mV have any effect on that?

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UpThyWazzoo replied to EA261WM doesn't power on

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08-06-2011, 07:22 PM
Re: EA261WM doesn't power on

I doubled-checked my measurements, and they were accurate. What is the voltage on pin 1 being compared to?

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Last edited by UpThyWazzoo; 08-06-2011, 07:42 PM.
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UpThyWazzoo replied to EA261WM doesn't power on

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08-06-2011, 06:26 PM
Re: EA261WM doesn't power on

How did you arrive at 2.48V? Did I measure something wrong

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UpThyWazzoo replied to EA261WM doesn't power on

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08-06-2011, 05:42 PM
Re: EA261WM doesn't power on

I'm not totally up to speed on how to test a zener diode, but the voltage drop from one end to the other is 16.9V and -16.9V when I switch the leads. This actually seems normal. I read 4.78V on pin 3, and 0 on pin 8?

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Last edited by UpThyWazzoo; 08-06-2011, 05:59 PM.
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UpThyWazzoo replied to EA261WM doesn't power on

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08-06-2011, 05:18 PM
Re: EA261WM doesn't power on

does this mean that the diode is shorting, or that something before the diode is putting out too many volts?

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UpThyWazzoo replied to EA261WM doesn't power on

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08-06-2011, 03:07 PM
Re: EA261WM doesn't power on

In general, how close is that IC to being "the end" of the power board? Are there any ICs that are identical in operation but might be easier to find?

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Last edited by UpThyWazzoo; 08-06-2011, 04:02 PM.
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UpThyWazzoo replied to EA261WM doesn't power on

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08-06-2011, 12:29 PM
Re: EA261WM doesn't power on

Q902 is an NPN transistor and it tested fine (19MOhm/Open, B-C, B-E) (Open/Open, C-E)

Also, IC901 is an [F] ek29 FAN7529. I believe this is the correct part: [url]http://www.fairchildsemi.com/pf/FA/FAN7529.html[/url]Re: EA261WM doesn't power on<br /> ...529.html[/url]

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Last edited by UpThyWazzoo; 08-06-2011, 01:03 PM.
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UpThyWazzoo replied to EA261WM doesn't power on

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08-06-2011, 10:01 AM
Re: EA261WM doesn't power on

Here's a link to the part info: [url]http://www.datasheetdir.com/LD7522PS+PWM-Controllers[/url]

With respect to Pin5:

Pin 1: 2.05V
Pin 2: 1.426V
Pin 3: 4.78V
Pin 4: 3.2mV
Pin 5: GND
Pin 6: 65.9mV
Pin 7: 16.9V
Pin 8: 0Re: EA261WM doesn't power on<br /> ...V<br /> Pin 5:

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Last edited by UpThyWazzoo; 08-06-2011, 10:17 AM. Reason: fixed measurements
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UpThyWazzoo replied to EA261WM doesn't power on

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08-06-2011, 09:38 AM
Re: EA261WM doesn't power on

Morning, Bill!

The part number is LD7522PS - 092855. Should I set about finding a 20 ohm resistor replacement?...

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UpThyWazzoo started a topic EA261WM doesn't power on

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08-06-2011, 08:06 AM
EA261WM doesn't power on

Hello all, it's been a while since I started my other thread on the VX2450 (which I still haven't been able to fix, unfortunately).

I'm sitting on what appears to be an almost-new NEC EA261WM that doesn't power on.

>The button LEDs do not light. Using a no-power Samsung thread from earlier,

>I've measured the mains filter cap (165V)

>I've measured the 12V and 24V pin outputs. They not 0 with respect to ground, but they are in the low 100mV or less--which I assume is just as good as 0. This indicates to me that the power board...

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UpThyWazzoo replied to How do i take apart my viewsonic VA2231w-LED?

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07-24-2011, 06:23 PM
Re: How do i take apart my viewsonic VA2231w-LED?

If you have real confidence in your ability to not break something, you may want to watch this: [URL="http://youtu.be/SZE_R8CPtM0"]http://youtu.be/SZE_R8CPtM0[/URL]. There is no guarantee that you'll be able to do the same exact thing to your monitor, but it does show how the housing works in general.

You may separate the two halves of your monitor housing by using a flat tool to pry them apart on the outside as shown in the video, or alternatively, you can start with lifting the inside edge of the front...

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EA261WM doesn't power on

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