Dell 1504FP monitor is blank

[Welchs101]

Hi,

I am trying to repair a dell Model # 1504FP monitor.

Observations:
1) power on the monitor and led-power-on light turns yellow. Then it turns green. But there is no image displayed on the screen.
2) With power-on led green i shined a flash light on the screen and you can see a faint image.

I took the monitor apart and there is nothing obviously wrong from a visual perspective (see pics of main board and inverter board).

I tested each of bulbs using a spare monitor to drive the bulbs.........ALL bulbs in the 1504FP are OK.

I put the monitor back together enough so i could power on the monitor and measure some voltages. I never actually measured anything because i found that device MTP2955V was getting hot.......see enclosed pic. I noticed that under this device there is some of that "glue" stuff that is supposed to kind yellowish in color i guess to hold devices in place. Anyway, i noticed that the glue stuff underthis device was more "brownish" in color........like it had gotten hot. Rate at which this device gets hot is not that fast but over about 1 to 2 min its almost too hot to touch with finger and it appears to increase in temp the longer its on.

I kept turning monitor off, to let MTP2955V cool, and then back on to see if any other devices were getting hot. As far as i can tell its the only one getting hot.

At somepoint during all of this on and off business the monitor decided to start working! I know this is monitor is still bad and needs fixing but thought this might be a clue.

Questions:
1) How to tell if device MTP2955V (its an ON semiconductor device) is bad?
2) MTP2955V is getting hot........should i replace this?
3) What voltages can i check to help determine location of the problem?

Any inputs you can give would be appreciated.

[Krankshaft]

Re: Dell 1504FP monitor is blank

That glue probably went conductive and destroyed the MTP2955V FET.

Desolder it scrape any remains of the old glue off it and the board then check it with the diode check of a DMM.

The solder joint on the cap on the inverter board is not done properly you should never have a bubble on the tip of the lead. Be sure to reflow it properly.

[PlainBill]

Re: Dell 1504FP monitor is blank

Hi,

I am trying to repair a dell Model # 1504FP monitor.

Observations:
1) power on the monitor and led-power-on light turns yellow. Then it turns green. But there is no image displayed on the screen.
2) With power-on led green i shined a flash light on the screen and you can see a faint image.

I took the monitor apart and there is nothing obviously wrong from a visual perspective (see pics of main board and inverter board).

I tested each of bulbs using a spare monitor to drive the bulbs.........ALL bulbs in the 1504FP are OK.

I put the monitor back together enough so i could power on the monitor and measure some voltages. I never actually measured anything because i found that device MTP2955V was getting hot.......see enclosed pic. I noticed that under this device there is some of that "glue" stuff that is supposed to kind yellowish in color i guess to hold devices in place. Anyway, i noticed that the glue stuff underthis device was more "brownish" in color........like it had gotten hot. Rate at which this device gets hot is not that fast but over about 1 to 2 min its almost too hot to touch with finger and it appears to increase in temp the longer its on.

I kept turning monitor off, to let MTP2955V cool, and then back on to see if any other devices were getting hot. As far as i can tell its the only one getting hot.

At somepoint during all of this on and off business the monitor decided to start working! I know this is monitor is still bad and needs fixing but thought this might be a clue.

Questions:
1) How to tell if device MTP2955V (its an ON semiconductor device) is bad?
2) MTP2955V is getting hot........should i replace this?
3) What voltages can i check to help determine location of the problem?

Any inputs you can give would be appreciated.

First of all, assume the MTP2995V is still good, at least for now. Second, remove it from the board and scrape all the glue away so none of it is contacting the leads, and remove the glue from the board, too. Then solder it back in and test the monitor. If the MTP2955V still gets hot, attach pictures bottom of the power supply board.

PlainBill

[Welchs101]

Re: Dell 1504FP monitor is blank

Will do! Thanks for the suggestions. I will let you know what happens.

[Krankshaft]

Re: Dell 1504FP monitor is blank

Be sure to take a pic of the bottom of the power board as Plainbill said.

I'm curious to see what this P Channel FET is for.

[momaka]

Re: Dell 1504FP monitor is blank

At somepoint during all of this on and off business the monitor decided to start working! I know this is monitor is still bad and needs fixing but thought this might be a clue.

That is actually a good clue which suggests that the caps might also be bad (they are CapXon brand after all, and those are well known to fail in LCD monitors). It's possible that while you were turning the monitor on and off, the caps heated up and their ESR went down just enough for the monitor to run.
Nonetheless, it's still probably a good idea to get that brown glue off of the MTP2955V IC as Krankshaft and PlainBill suggested.

[Welchs101]

Re: Dell 1504FP monitor is blank

Good news!

I resoldered the caps on the inverter. From the enclosed pic the solder still looks a little round but its nothing like it was before. Looks a lot better.

I also cleaned up the MTP2955V. I took it off the board. Cleanedup the board and the part itself. Looks good.

I reassembled everything and it worked........but more importantly......it worked with out the MTP2955V getting hot!

Thanks guys!

[Welchs101]

Re: Dell 1504FP monitor is blank

If i did not include a pic that you want just let me know. I wont put back everything until tomorrow so just let me know.

[Welchs101]

Re: Dell 1504FP monitor is blank

Forgot to include pics in my earlier post.

[Welchs101]

Re: Dell 1504FP monitor is blank

I put a red box around the MTP2955V as seen from the back side.

[Krankshaft]

Re: Dell 1504FP monitor is blank

Great job!

You lucked out that the adhesive wasn't heavily on the first pin (the gate) of the FET or it probably would have blown. FETs have a very thin oxide coating on their gates it doesn't take much to blow it off and create a short from source to drain.

[bev]

Re: Dell 1504FP monitor is blank

re dell 1504fp
found this thread, as I had same problem with screen blanking out. Only problem found was the glue on the MTP2955V as shown in second jpeg from welchs101 post. Cleaned it off, and monitor works ok. Thanks everyone. My qeuestion is should I replace caps? They look OK.

[PlainBill]

Re: Dell 1504FP monitor is blank

re dell 1504fp
found this thread, as I had same problem with screen blanking out. Only problem found was the glue on the MTP2955V as shown in second jpeg from welchs101 post. Cleaned it off, and monitor works ok. Thanks everyone. My qeuestion is should I replace caps? They look OK.

Your call. Which would you prefer to do - replace them now for about $10.00 or open the monitor up again when they go bad?

PlainBill

[Hw00d]

Re: Dell 1504FP monitor is blank

gosh I luv this place....when I get stumped (ya, it happens ) I come here and problem gets resolved in a few minutes!!..thanks badcaps!!

very familiar w/ this monitor because I just recapped this one about 2 months ago (in shop use on a bench) and then the dreaded flashy/2-3 second screen yesterday. So it came as a surprise this was now happening. Turns out, same culprit, crappy glue around the FET, cleaned up and works again...thanks again all!!!