BenQ FP737s - full of bad caps

[trodas]

My BenQ FP737s suddently lose brightness to about half of it and then after a second or so it went completely black.
While the power led is on, no reaction on menu press or anything.

From this time everytime I tried to power it on, it just show up the logo boot screen (maybe a bit dimmer that usual?) and then the half brightness of the computer screen (never go to full brightness again) and then - after a second - it again went black.

Repeatable.

So I open the monitor up and check on the caps, as I smell the caps. All known bad brands:

BenQ FP737s
-----------
1x 100uF 450V d18-22.5x41-47 VENT - Nichicon LS 180uF d22x45 493-2607-ND
5x 470uF 35V d10 Elite - Nichicon HW 493-6882-ND
2x 1000uF 16V d10 Elite - Nichicon HM UHM1C102MPD-ND
1x 1000uF 10V d10 Elite - Nichicon HE 493-1497-ND
2x 220uF 25V d8-10 Lelon - Nichicon HE 680uF 493-1554-ND
1x 100uF 25V d6.3 Lelon - Nichicon HE 493-1548-ND
3x 47uF 35V d5 Leon - Panny FC P11232-ND
2x 47uF 25V d5 Elite - Panny FM P12923-ND
5x 22uF 25V d5-6.3 Jamicon + Elite - Panny FC P11213-ND
1x 4.7uF 25V d5 Lelon - Panny FC 50V P10315-ND
3x 2.2uF 50V d5-6.3 Elite - Panny FC P10313-ND
3x 1uF 50V d5-6.3 Jamicon - Panny FC P10312-ND

However none of them is leaking or even bulging. I looked up for some replacements as is clear from the list above, but not quite sure if it is worth recap, because the LCD is acting up weird.

I did a lot of recaps, and I'm not affraid of it, I just asking the public to share some of your experiences on how the BenQ or LCDs in general acting up to get confirmed, that my experience is not unusual.

Or it is?

PS. the LCD is about 4 years old, 3 years from it did not used.

[spidey]

Re: BenQ FP737s - full of bad caps

Most probably this is a ccfl problem. your inverter circuit or bad ccfl light(s) or maybe a broken / bad /cold solder joint.

[budm]

Re: BenQ FP737s - full of bad caps

Pictures of the board? Have to test the High Voltage winding resistance of the inverter transformers, and possibly bad lamp assemblies as mention.
Example of bad lamps:
http://s807.photobucket.com/user/bud...?sort=3&page=1

Transformers:
http://s807.photobucket.com/user/bud...?sort=3&page=1

[trodas]

Re: BenQ FP737s - full of bad caps

spidey - cannot find anything like that... Also that won't explain why the monitor refuse to react in any way to the buttons.


budm - I will took pictures later, I was disgusted and packed the diassembed monitor right away from my sight. I did not like it...
However High VOltage windings on the transformers or bad lamp assembly did not explain, why the screen goes completely black and why there is no menu reaction at all. I mean - if the backlight is the only one problem, then why the rest is failing?

Luckily, all the caps need are available and therefore I try recap and we see, if something else is bad, except caps. I slightly bumped the input cap capacity, witch should give the monitor more life I hope... (if it will work)

Thanks budm for very interesting (and terrible) pictures of the lamp failures! And transformers... very interesting! IIRC there are four of the transformers and two connections for the lamps. None of that seems damaged or overheated in any way, shape or form.

[newtothis]

Re: BenQ FP737s - full of bad caps

Had exactly the same symptoms on an LG W2246 just yesterday, Fired up, quick logo, dimmed and then went black, Checked the caps and visually looked fine.... discharged all the caps then tested with my ESR meter and 2 1000uf 16v and 2 1000uf 25v read around 0.80... should of been around 0.1. Changed them and problem was solved... went on to change all caps to make sure it had a longer life.

So my advice is to check via ESR readings.

[Behemot]

Re: BenQ FP737s - full of bad caps

Sometimes not even ESR revelas problem. Just recently got Acer AL1916W with inverter problems, repalced caps even though they've read fine and problem solved again. Gioing with "bad cap=replace on sight" usually works.

Anyway, does this also have the famous push-pull inverter?

[budm]

Re: BenQ FP737s - full of bad caps

"why the screen goes completely black and why there is no menu reaction at all. I mean - if the backlight is the only one problem, then why the rest is failing?" If the screen is high contrast type when you use the flashlights to see if you can see the menu will be almost impossible to see. Bad main board will not cause half dimming screen, you can force on the backlights manually if you want to verify if you gave bad inverter/lamps problem or not. You can also make inverter test lamps to verify the function of the inverter section. Inverter outputs are Royer Osc SETUP.

Service manual: Made by BenQ