Dell E177FPv - No signs of Life

[alexanna]

Re: Dell E177FPv - No signs of Life

If you have an ohmmeter a very simple quick test would be to see if its shorted.
If you have another capacitor of the same values try changing it

[jetadm123]

Re: Dell E177FPv - No signs of Life

Diodes D12 and D13 (right above U6 and U7). Can you verify they feed the input of U6 and U7? Check to see if one of them is open or shorted.

[jayoung]

Re: Dell E177FPv - No signs of Life

If you have an ohmmeter a very simple quick test would be to see if its shorted.
If you have another capacitor of the same values try changing it

C62 is a 22uf 25V capacitor. I have a spare 22uf 50V Panasonic FM series if you think that would be OK. The resistance between the positive and negative leads in circuit is 755 ohms.

Diodes D12 and D13 (right above U6 and U7). Can you verify they feed the input of U6 and U7? Check to see if one of them is open or shorted.

Voltage and Resistance on the diodes:
D13 - 1.19 - 1.25 VDC TOP
1.71 - 1.77 VDC BOTTOM
39500 OHMS
D12 - 5.17 VDC TOP
1.71 - 1.77 VDC BOTTOM
10230 OHMS

[alexanna]

Re: Dell E177FPv - No signs of Life

The voltage is way too low on the input of the left regulator, but I don't know why. At the moment I am out of ideas.
The higher voltage cap would work if you decide to try it.

[jsog]

Re: Dell E177FPv - No signs of Life

That 1.71 - 1.77 V on both diodes looks odd. Is that with the black probe on a ground like the screw hole to the right of U6?

[jetadm123]

Re: Dell E177FPv - No signs of Life

Okay, here's what I'm thinking:


U6 appears to be an adjustable regulator. Using your methodology, the top pin is the input voltage (5 volts). Middle pin is the output (3.3 V). Bottom pin is the adjustment pin (2.1 V). The bottom pin requires two resistors to set the output voltage. It looks like everything is working as you're getting the 3.3volt output. At the output of U6 should be a small cap.

I'm assuming that the output of U6 feeds the input of U7, which in your case is reading appprox 1.2 V instead of 3.3 V. Now, if something's wrong with the small cap, then it's logical to assume the input to U7 will be affected.


To determine if the output of U6 is connected to the input of U7, with power off and your meter set to resistance, place one probe on the middle pin of U6 and the other probe to the top pin of U7. If you get zero ohms, then you've verified they are connected. To find out which cap is connected to the output of U6, perform the same test as above, except place your probe on the various caps "+" lead to determine which cap will give you zero ohms. Try replacing this cap to see if it solves your problem.

[alexanna]

Re: Dell E177FPv - No signs of Life

Well after some sleep and dreaming about your monitor!
After you did the recap and assembled everything it worked for a while, Makes me wonder about a poor connection.
With everything hooked up and power and a signal applied, try gently flexing the logic board in various places, I would pay close attention to areas around the voltage regulator with the low input voltage.
For me a plastic chopstick works great, but anything that's well insulated would work, just gently poke around see if the voltage changes.

[jayoung]

Re: Dell E177FPv - No signs of Life

Well after some sleep and dreaming about your monitor!
After you did the recap and assembled everything it worked for a while, Makes me wonder about a poor connection.
With everything hooked up and power and a signal applied, try gently flexing the logic board in various places, I would pay close attention to areas around the voltage regulator with the low input voltage.
For me a plastic chopstick works great, but anything that’s well insulated would work, just gently poke around see if the voltage changes.

I got home from work today and hooked up the power and video board along with the front control board. I pushed on the video board around all areas with no change.

The voltage is way too low on the input of the left regulator, but I don’t know why. At the moment I am out of ideas.
The higher voltage cap would work if you decide to try it.

I replaced C62 with the 22uf 50V Panasonic FM. I also reflowed the solder on the two diodes and the two voltage regulators.

That 1.71 - 1.77 V on both diodes looks odd. Is that with the black probe on a ground like the screw hole to the right of U6?

All of the voltage readings were taken with the black probe on a screw hole.


After replacing the C62 capacitor and reflowing the two diodes and the two voltage regulators, I re-assembled the monitor without the lcd and the power LED came on when pressed. I finished assembling the monitor and the backlights came on, but no video. I re-seated the ribbon cable from the front control panel and everything seems to be working now. I am typing this message using the monitor and it has been up and running for about 45 minutes now. I will continue to use it for a bit to see if anything changes before snapping the front cover back on (it was a bear to get off in the first place).

A VERY big thank you to alexanna, jetadm123, and jsog for all their help. I'm not sure if it was the capacitor or a loose solder joint at one of the two diodes or two voltage regulators since I did not test the monitor between performing all of those fixes.