Dell E177FPv - No signs of Life

[jayoung]

I have a Dell E177FPv that does nothing when powered and plugged into a working computer. The on/off button does nothing when pressed and shows no lights.

The two fuses (F1 and F151) on the board have been checked and show continuity.

The voltage across the main capacitor reads 164.8 - 165.1 VDC.

The 8 pins going to the video display board read:
pin 1 (labeled +5.1V/1.6A) - 5.19 VDC
pin 2 (labeled +5.1V/1.6A) - 5.20 VDC
pin 3 (labeled GND) - 0 VDC
pin 4 (labeled GND) - 0 VDC
pin 5 (labeled NC) - 0 VDC
pin 6 (labeled BRIG -A) - 4.98 VDC
pin 7 (labeled BRIG -P) - 3.53 VDC
pin 8 (labeled ON/OFF) - 0 VDC

Q205 and Q208 were tested in circuit and are not shorted.

Q1 was tested in circuit and is not shorted.

I have replacements for the 8 capacitors on the power board, but have not replaced them as of yet. I was trying to determine the cause of getting nothing from the monitor when the power button was pushed. Any help would be greatly appreciated.

[alexanna]

Do you feel the power button clicking when you push it?

[jayoung]

Originally Posted by alexanna

Do you feel the power button clicking when you push it?

Yes, I even took the board out of the front cover and pushed it to make sure. All of the control buttons click when they are pushed.

[alexanna]

There are probably 5 pins that go to the front panel switch,At least 1 should show some voltage around 2 or 3 volts?
Do any of the voltages go low to 0 volts as you press the power button?

[jayoung]

Originally Posted by alexanna

There are probably 5 pins that go to the front panel switch,At least 1 should show some voltage around 2 or 3 volts?
Do any of the voltages go low to 0 volts as you press the power button?

There is a ribbon cable that goes to the front panel:

Pin 1 - reads 3.20 VDC constant pushing the power button
Pin 2 - reads 3.30 VDC and goes to 0 VDC while the power button is pushed, then goes back to 3.30 VDC when I let go
Pin 3 - reads 3.21 VDC constant pushing the power button
Pin 4 - reads 3.23 VDC constant pushing the power button
Pin 5 - reads 0 VDC
Pin 6 - reads 0 VDC
Pin 7 - reads 0 VDC

[alexanna]

Pin 2 is the on /off pin,looks like it's doing what it's suppose to do.
The power LED is not on any color?

[jayoung]

Originally Posted by alexanna

Pin 2 is the on /off pin,looks like it's doing what it's suppose to do.
The power LED is not on any color?

Nope, no color to the LED.

[alexanna]

I’m getting close to running out of ideas.
It looks like there are a couple of voltage regulators on the logic board.
See if there’s numbers on them to identify them, and measure the voltages.

[jetadm123]

I would consider checking the 2 voltage regulators on the logic board. I believe they are U6 and the similar 3-pin device to the left of it. Please list the voltage readings for each leg and the part number off of each device.

Oops! Alexanna beat me to it!

[jayoung]

Originally Posted by alexanna

I’m getting close to running out of ideas.
It looks like there are a couple of voltage regulators on the logic board.
See if there’s numbers on them to identify them, and measure the voltages.

Sorry it took a little while, I went ahead and re-capped the power board.

Part No. 6J2L 1117L

Measurement taken with the power board and video board connected together out of the case (they are upside down and in-accessible installed). Power hooked up but no video.

U6:
top pin - 5.17 VDC constant
middle pin - 3.34 VDC constant
bottom pin - 2.09 VDC constant

to the left:
top pin - 1.19 - 1.24 VDC moving
middle pin - 0.38 - 0.45 VDC moving
bottom pin - 0.12 - 0.14 VDC moving

[alexanna]

Originally Posted by jayoung

Sorry it took a little while, I went ahead and re-capped the power board.

Part No. 6J2L 1117L

Measurement taken with the power board and video board connected together out of the case (they are upside down and in-accessible installed). Power hooked up but no video.

U6:
top pin - 5.17 VDC constant
middle pin - 3.34 VDC constant
bottom pin - 2.09 VDC constant

to the left:
top pin - 1.19 - 1.24 VDC moving
middle pin - 0.38 - 0.45 VDC moving
bottom pin - 0.12 - 0.14 VDC moving

Looks like the voltage regulators are adjustable.
The input voltage on the left regulator really looks low.
Can you check to see if a filter cap is in the circuit to pin 1 of the left regulator?
If there is a cap involved, you should check to see if it’s shorted.

[jayoung]

Update to the status:

As mentioned before, I re-capped the power board before I gave you the voltage measurements on the regulators. After that, I figured I would put the monitor back together enough to see if there was any change after the re-cap. The monitor worked perfectly including the LED. I ran upstairs to put my kids in bed and when I returned, the monitor was off with no sign of life again, no LED either. I will have to open it back up and see if possibly a fuse blew or something along those lines, or I'm back to where I started. Thanks for all the help alexanna and I'll post again probably tomorrow when I get it opened back up.

[jayoung]

Update again:

I took the monitor completely apart and checked the 2 fuses, voltage across the main cap, voltage on the 8 pins to the video board, checked for shorts on Q205, Q208, and Q1, voltage on the 7 wires on the ribbon to the control board, and the voltage at the 2 regulators. Everything reads the same as before and there is NO sign of life to this monitor. I'm not sure why it worked for a little while after I reassembled it after I re-capped the power board.

alexanna - I cannot follow the circuit to pin 1 of the left voltage regulator, there are no traces on the top or the bottom of the board, I would guess they are between the layers and not on either surface. I'm not sure if I can find a schematic of the board or not.

Any ideas would be greatly appreciated.

[alexanna]

There are times you can trace a circuit with a voltmeter.If you see the 1.9 volt on pin 1 of the regulator,Carefully probe around the board and see if you can find it at another point.
Check what voltage you have on the positive leads of the capacitors.

[alexanna]

I seriously doubt this is your problem, but it won’t hurt to try.
Disconnect the flat ribbon cable from the logic board to the LCD panel; there is voltage on some of the pins so keep it insulated.
Dose the behavior of the front PLED change, with the ribbon disconnected?

[jetadm123]

You say you recapped the board. What brand/series caps did you use? Did you verify correct polarity and are all capacitor joints properly soldered?

[jsog]

The left regulator is U7. Is there any more text on the label? In that orientation, the top pin is input, the middle pin is output, the bottom pin ground (or adjusted). Does "moving" mean moving up and down?

Guessing that's a 1.8V regulator, which should be getting 3.3V input from U6. The regulator itself might be bad. Sometimes ceramic caps short; C64 and C65 are worth checking. Testing or just replacing the electrolytics on that board is another option.

[jayoung]

Originally Posted by alexanna

There are times you can trace a circuit with a voltmeter.If you see the 1.9 volt on pin 1 of the regulator,Carefully probe around the board and see if you can find it at another point.
Check what voltage you have on the positive leads of the capacitors.

The only point on the back of the board that I can find 1.19 VDC is at the positive side lead of C62. It's a little more difficult to take readings on the front of the board with it plugged in.

Going left to right, top to bottom on the picture of the video board (some of the caps have multiple designations near them):

C20 0.41 - 0.44 VDC
C63 0.42 - 0.45 VDC
C62 1.22 - 1.25 VDC
C55 5.17 VDC
C54 5.17 VDC
C26 0.43 - 0.46 VDC
C27 3.34 VDC
C13 3.34 VDC
C56 3.34 VDC
C38 3.34 VDC
C68 0.00 VDC

Originally Posted by alexanna

I seriously doubt this is your problem, but it won’t hurt to try.
Disconnect the flat ribbon cable from the logic board to the LCD panel; there is voltage on some of the pins so keep it insulated.
Dose the behavior of the front PLED change, with the ribbon disconnected?

I have tried it with and without the ribbon cable attached to the panel - no change.

Originally Posted by jetadm123

You say you recapped the board. What brand/series caps did you use? Did you verify correct polarity and are all capacitor joints properly soldered?

All 8 were replaced with Panasonic FM series caps. Polarity is correct. The solder joints should be in good shape.

Originally Posted by jsog

The left regulator is U7. Is there any more text on the label? In that orientation, the top pin is input, the middle pin is output, the bottom pin ground (or adjusted). Does "moving" mean moving up and down?

Guessing that's a 1.8V regulator, which should be getting 3.3V input from U6. The regulator itself might be bad. Sometimes ceramic caps short; C64 and C65 are worth checking. Testing or just replacing the electrolytics on that board is another option.

The only other thing on it is an AC inside of a swish (company logo I would assume). Moving I mean by the voltage changes up and down as I take the reading. I only have a voltage meter and no other testing equipment, so it may have to be change them out.

[alexanna]

Do you have a way to check C62?

[jayoung]

Originally Posted by alexanna

Do you have a way to check C62?

Check it which way?