EA261WM doesn't power on

[UpThyWazzoo]

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.

[PlainBill]

Re: EA261WM doesn't power on

Oy!!!

PlainBill

[UpThyWazzoo]

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" ?

[PlainBill]

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" ?

The startup cap is C917. I checked 'A2' in several cross references, but didn't come up with anything that matches this application.

PlainBill

[UpThyWazzoo]

Re: EA261WM doesn't power on

there are other diodes marked with "A2" on the board. Could they possibly be this: http://jinghenggroup.en.alibaba.com/...ode_A1_A7.html ?

[alexanna]

Re: EA261WM doesn't power on

Is you measurement 21.9 OHMS or 21.900
You might try, carefully lift one end of the diode, and measure it again.

[UpThyWazzoo]

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.

[UpThyWazzoo]

Re: EA261WM doesn't power on

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

[PlainBill]

Re: EA261WM doesn't power on

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

While strictly speaking, it isn't necessary to replace it, I will admit that doing so has a certain esthetic appeal. Measure the size to determine the wattage, then move up at last one step. Don't put in anything over 25 watts.

PlainBill

[UpThyWazzoo]

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 out of the wall outlet cause this?

[PlainBill]

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 out of the wall outlet cause this?

I haven't really examined this portion of the circuit, but in general there are three explanations:

1. Poor design - the wattage was insufficient for the application.

2. Good design, but improper assembly. Higher wattage resistors are often elevated above the board. Those components are usually hand inserted. Someone in the assembly area decided it should be installed flush to the board.

3. Something failed and resulted in a higher current flow through the resistor.

I'd say it was either 1 or 2, buy a higher wattage resistor, and elevate it from the board.

PlainBill

[UpThyWazzoo]

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

[UpThyWazzoo]

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?

[stojna]

Re: EA261WM doesn't power on

and ? what happened?

[UpThyWazzoo]

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