intermittent fault on my Miria T27004 monitor

[Paul Kelly]

I have an intermittent fault on my Miria T27004 monitor

http://www.mirai.eu/Uk/ProductDetail...d=34&cat_id=51

If the monitor has been resting it powers up fine but after it has been used for a while or if it is powered down and back on or the input is changed the screen is dark then slowly a band of thin vertical lines appears red blue and green. And the audio output is buzzing. If I rest the monitor it will power up again I have visually checked the caps but they look OK any one have any suggestions as to what too look at

[PlainBill]

Re: intermittent fault on my Miria T27004 monitor

I have an intermittent fault on my Miria T27004 monitor

http://www.mirai.eu/Uk/ProductDetail...d=34&cat_id=51

If the monitor has been resting it powers up fine but after it has been used for a while or if it is powered down and back on or the input is changed the screen is dark then slowly a band of thin vertical lines appears red blue and green. And the audio output is buzzing. If I rest the monitor it will power up again I have visually checked the caps but they look OK any one have any suggestions as to what too look at

The buzzing audio output is a definitive sign of power supply problems. Note that many manufacturers have mastered the art of building caps that fail without giving any external signs.

Pictures, pictures, pictures.

PlainBill

[Paul Kelly]

Re: intermittent fault on my Miria T27004 monitor

A failing power supply was my first thought. But I have a friend who has the same monitor and the power supply for this model is a unit housed into the case I have swopped with him and mine is working fine his gives the same result.

What do you need pics of and Ill post them

[retiredcaps]

Re: intermittent fault on my Miria T27004 monitor

But I have a friend who has the same monitor and the power supply for this model is a unit housed into the case I have swopped with him and mine is working fine his gives the same result.

What do you need pics of and Ill post them

1) 1) Post clear focused pictures after reading

https://www.badcaps.net/forum/showthread.php?t=1868

2) Please do not post pictures inline as they slow down the loading of pages.

3) For best picture quality and clarity take your boards to a window on a sunny day, turn flash off, and use macro mode. Take a top down view of all your boards (front and back). Make sure the photo is legible so that we can read the PCB printing clearly. A shutter speed of 1/125 or faster will produce nice clear focused pictures. Try to get a photo that is 2000x2000 resolution or as close as possible.

4) Here is an example of the pictures we want.

https://www.badcaps.net/forum/showpo...94&postcount=1

5) The voltage regulators on the logic card could be failing.

6) The caps on the logic card could be failing.

[Paul Kelly]

Re: intermittent fault on my Miria T27004 monitor

Thanks guys for the quick replies I appreciate it

I will post the photos tomorrow of all the boards

I have purchased today a new set of caps for the logic board and will replace them tomorrow and post the results

[retiredcaps]

Re: intermittent fault on my Miria T27004 monitor

I have purchased today a new set of caps for the logic board and will replace them tomorrow and post the results

If you have an identical lcd, the next thing to do is to swap logic boards. That would rule out another board and possibly point at the panel itself. That is, if I understand the board swap correctly in the previous post.

[Paul Kelly]

Re: intermittent fault on my Miria T27004 monitor

The swapping of the power supply was done while I was In Dublin a week ago and the second monitor is not available too me now.

I note the comments about the failing Voltage regulator and looking at the logic board I can see a discoloration on the board under the HS901 and this I think is the heat sink for a voltage regulator is that correct ? (sorry but I only have a very basic knowledge of circuits) if so maybe it would be better to replace this before the caps and see if that solves the problem

I have attached pics

Thanks for all the help guys

[jetadm123]

Re: intermittent fault on my Miria T27004 monitor

Maybe I misunderstood, but in post #3 you said you swapped power supplies with your friend and your monitor worked without problems. Therefore, if the power supply is the problem, why are we looking at the logic board?

[Paul Kelly]

Re: intermittent fault on my Miria T27004 monitor

Sorry probably me confusing things I swopped the power supply with another unit and the fault was the same on mine and the other monitor ran perfectly well. On this monitor the power supply is a unit in its own box housed under a separate cover and can be plugged in and out without taking the back off

[jetadm123]

Re: intermittent fault on my Miria T27004 monitor

There may be more than one voltage regulator on your logic board. What are the part numbers for U201,202,301 located middle of board? Part number for U203 located lower right. Part number for U401 at bottom of board.

[Paul Kelly]

Re: intermittent fault on my Miria T27004 monitor

U201 is -5JCL 17-25L

U202 is -5KGL 17-33L

U301 is -5JCL 17-25L

U203 is -5KGL 17-33L

U401 is -PF7AL FDS 9435A

[jetadm123]

Re: intermittent fault on my Miria T27004 monitor

U201 is -5JCL 17-25L

U202 is -5KGL 17-33L

U301 is -5JCL 17-25L

U203 is -5KGL 17-33L

U401 is -PF7AL FDS 9435A

Using a mounting screw for your ground probe, measure and record the voltage at each leg for U201-203 and U301.

As for U401, it looks like you gave the part # for Q401 because looking at your photo I can vaguely make out 1084-?....Anyway, go ahead and please measure and record the voltages at the 3 legs of U401.

[Paul Kelly]

Re: intermittent fault on my Miria T27004 monitor

Sorry the art number for U401 is 1084-50 0547AL

These are the results just to make sure I am doing this right the meter is set to DC 20. The number 1 pin is on the left and I'm working to the right


1 2 3

U201 0 2.49 5.03

U203 0 3,29 5.03

U301 0 2.49 5.03

U401 0 5.03 6.64


Thanks again for the help

[Paul Kelly]

Re: intermittent fault on my Miria T27004 monitor

The formatting seems to have gone wrong in the post here they are again


U201
1= 0
2= 2.49
3= 5.03

U203
1= 0
2= 3,29
3= 5.03

U301
1= 0
2= 2.49
3= 5.03

U401
1=0
2=5.03
3= 6.64

[jetadm123]

Re: intermittent fault on my Miria T27004 monitor

The formatting seems to have gone wrong in the post here they are again


U201
1= 0
2= 2.49
3= 5.03

U203
1= 0
2= 3,29
3= 5.03

U301
1= 0
2= 2.49
3= 5.03

U401
1=0
2=5.03
3= 6.64

Looks like the regulator outputs are good. I'm starting to wonder if the LCD panel itself is the problem. You said the lines don't appear for a while. May I suggest trying to accelerate the problem by heating up the logic board with a hair dryer? If you get the lines in short order with the hair dryer, then we can suspect the logic board. If not, then try heating along the top inner edge of the LCD panel. I'm suspecting that the flat ribbbon cables that run the top width of the LCD display are started fail at the weld/solder points. This type of failure is not repairable.

If none of the above reproduces the problem, I would try replacing the 8 electrolytic caps with something like a low-esr panasonic FM or FC series cap.

[Paul Kelly]

Re: intermittent fault on my Miria T27004 monitor

I have tried heating the places you suggested several times and there is no discernable difference in the time the fault occurs

I have replaced the eight caps on the logic board and the fault remains

Any other suggestions

[jetadm123]

Re: intermittent fault on my Miria T27004 monitor

I have tried heating the places you suggested several times and there is no discernable difference in the time the fault occurs

I have replaced the eight caps on the logic board and the fault remains

Any other suggestions

Whew! At this point I don't really have any other ideas. Maybe one additional test you can perform is when you get the vertical lines, try gently pushing down with your finger on the line at the top portion of the screen. If the line goes away, then you've found your problem.

[Paul Kelly]

Re: intermittent fault on my Miria T27004 monitor

No the line does not go away if I press on the screen what does this mean if they do a faulty panel ?

Thanks for all the help