Dell LCD E198WFPF no power

[PlainBill]

Re: Dell LCD E198WFPF no power

I see. Thanks for the explaination. I found my oscilliscope yesterday. However, I cannot find the probe. I think I placed those in some other location. I will try to find those probes today and see what the processor got.

I've had days like that. I STILL haven't found my isolation transformer.

PlainBill

[albertwong]

Re: Dell LCD E198WFPF no power

I found my probes and checked the board.
I connected the probe to both pins of the crystal instead of the processor. The pins on the processor is just so small that I am scared that I will short some pins when I measure.
I seems like there are signals.
Please see the attached pictures.
By the way, I was using channel 2 of the scope.

[PlainBill]

Re: Dell LCD E198WFPF no power

I found my probes and checked the board.
I connected the probe to both pins of the crystal instead of the processor. The pins on the processor is just so small that I am scared that I will short some pins when I measure.
I seems like there are signals.
Please see the attached pictures.
By the way, I was using channel 2 of the scope.

The amplitude is good, but it looks to me like you have a frequency of about 70 Khz. The doesn't make sense. I would have expected 14 Mhz.

PlainBill

[pedro]

Re: Dell LCD E198WFPF no power

The amplitude is good, but it looks to me like you have a frequency of about 70 Khz. The doesn't make sense. I would have expected 14 Mhz.

PlainBill

It's unclear whether the x10 is selected on amplitude or TB, Bill. But 2.5div of amplitude at 50mV/div is a bit short.

Certainly that isn't the waveform I'd expect on either xtal pin. Something wrong - wrong pin maybe, or the oscillator circuit trying to excte the xtal? I'd like the OP to zoom in on those included angles after the H-L transitions, as it may be the oscillator trying to start at xtal freq.

[PlainBill]

Re: Dell LCD E198WFPF no power

It's unclear whether the x10 is selected on amplitude or TB, Bill. But 2.5div of amplitude at 50mV/div is a bit short.

Certainly that isn't the waveform I'd expect on either xtal pin. Something wrong - wrong pin maybe, or the oscillator circuit trying to excte the xtal? I'd like the OP to zoom in on those included angles after the H-L transitions, as it may be the oscillator trying to start at xtal freq.

You could be right; I was assuming a 10X probe.

PlainBill

[albertwong]

Re: Dell LCD E198WFPF no power

Yes, it is 10x probe.
I connected my probe to both pins behind the crystal on the board. Is that how I should connect? I did not connect to the processor.

So how should I change the setting on my scope?
I had a hard time making my scope work. I will take a full picture of the face panel of my scope tonight so that you can have a better idea of what setting I have.

Let's say if the frequency of the crystal is not right, then could it be the crystal not working?
Should I replace the crystal?

Hi Bill, I just saw that you will be having a cataract surgery on May 19, 2010. I wish everything will be going smooth and you will recover soon.

[PlainBill]

Re: Dell LCD E198WFPF no power

Yes, it is 10x probe.
I connected my probe to both pins behind the crystal on the board. Is that how I should connect? I did not connect to the processor.

So how should I change the setting on my scope?
I had a hard time making my scope work. I will take a full picture of the face panel of my scope tonight so that you can have a better idea of what setting I have.

Let's say if the frequency of the crystal is not right, then could it be the crystal not working?
Should I replace the crystal?

Hi Bill, I just saw that you will be having a cataract surgery on May 19, 2010. I wish everything will be going smooth and you will recover soon.

Connect the scope ground to circuit board ground. Connect the scope probe to either side of the cap. One side should give a stronger signal; use that side.

PlainBill

[Radio Fox]

Re: Dell LCD E198WFPF no power

The timebase is uncallibrated in your photo. Turn the orange variable knob on the TIME/DIV fully clockwise to the CAL'D position.

Measure the Xtal as PlainBill says. Try to do it without the extra red croc clip lead. This will give a clearer image.

[albertwong]

Re: Dell LCD E198WFPF no power

Here is a full picture of what control I have in my scope.

[albertwong]

Re: Dell LCD E198WFPF no power

I measured it again with the new suggestion.
I turned the TIME/DIV fully clockwise to the CAL'D position.
connect ground of the scope to the board ground and connect the probe to either side of the crystal. The ground of the probe is not connected.

I got some signals. But not matter how I turn the delay, the wave won't stop moving. I cannot stabilize the display.

I took a picture of it.
10x probe
.1V/Div

[PlainBill]

Re: Dell LCD E198WFPF no power

I measured it again with the new suggestion.
I turned the TIME/DIV fully clockwise to the CAL'D position.
connect ground of the scope to the board ground and connect the probe to either side of the crystal. The ground of the probe is not connected.

I got some signals. But not matter how I turn the delay, the wave won't stop moving. I cannot stabilize the display.

I took a picture of it.
10x probe
.1V/Div

Some suggestions:
1. Upper right corner. Set Sweep Mode to Norm; Source to Ch2.
2. Upper center, set Hor Display to A
3. 'A Time / Div and Delay Time'. Make sure red knob is pushed in and rotated fully clockwise.
4. Adjust Holdoff knobs to stabilize the display. Adjust gray knob under 'A Time / Div and Delay Time' to show several cycles of the waveform.

PlainBill

[albertwong]

Re: Dell LCD E198WFPF no power

Some suggestions:
1. Upper right corner. Set Sweep Mode to Norm; Source to Ch2.
2. Upper center, set Hor Display to A
3. 'A Time / Div and Delay Time'. Make sure red knob is pushed in and rotated fully clockwise.
4. Adjust Holdoff knobs to stabilize the display. Adjust gray knob under 'A Time / Div and Delay Time' to show several cycles of the waveform.

PlainBill

Thx for the suggestion.
A few questions.
Can you explain a little bit more about what the sweep mode, source and hor Display is?
I am always curious about what are those.
Also, on the holdoff knobs, there is a grey small knob on top of the big one. What's the different?
WHen I first got the scope, I was having a hard time stablilzing the screen. So I am thinking it is not working properly. May be I just have the wrong setting.
Thx for teaching me so much.

[albertwong]

Re: Dell LCD E198WFPF no power

I have just checked the crystal with the new settings.
Here is what I got.
I think there is some signal from the crystal.

[PlainBill]

Re: Dell LCD E198WFPF no power

I have just checked the crystal with the new settings.
Here is what I got.
I think there is some signal from the crystal.

I agree.

PlainBill

[albertwong]

Re: Dell LCD E198WFPF no power

So is there anything else I can check?

[PlainBill]

Re: Dell LCD E198WFPF no power

So is there anything else I can check?

Nothing that I can think of. Perhaps in the near future, however.

I've got an identical problem with another Dell monitor, a E177FPf. The interesting thing is it's a totally different system. Power supply, inverter and logic all on one board. The processor chip is also different. I'm going to be going over it carefully to see if I can figure out what is going on. The only thing I can think of trying is reinitializing the EEPROM.

PlainBill

[albertwong]

Re: Dell LCD E198WFPF no power

reinitializing the EEPROM?
Sounds like some special programming device is needed.

[PlainBill]

Re: Dell LCD E198WFPF no power

reinitializing the EEPROM?
Sounds like some special programming device is needed.

Not necessarily. On many monitors you can do a reset by holding down certain buttons, then plugging it in. I'm not at all sure that that will work in this case, usually a monitor with a corrupted eeprom will at least flash the power button.

PlainBill

[albertwong]

Re: Dell LCD E198WFPF no power

Do you know if I can obtain the service manual for this monitor anywhere?

[EGuevarae]

Re: Dell LCD E198WFPF no power

Do you know if I can obtain the service manual for this monitor anywhere?

Would be very (VEEEEERYYYYYY) difficult