Squealing LCD....?

[stevo1210]

Hello Everyone,

I have a BenQ FP937S LCD panel display that squeals in standby mode!!
It's under warranty so i'll bring it to the repair center.
Does anyone have an idea to what this high pitch squealing is so i can tell the technician what to fix before i have to go there again for the same issue....

Also, I've seen a panel that sometimes goes all white and nothing else appears but white it even stays white when the buttons are pressed. Sometimes when it works properly, I can see pixel lines appear.
But at the moment it's fine again?
Anyone got an idea to whats dead/ going to die sooner or later?
I'm only guessing that the panel is dead and the mainboard still works since it responds to the computer being on and off etc. , when it goes all white ?

Hitting it doesnt change anything at all.... i had a Sony LCD that kept on going purple , a while ago , turns out that had a loose internal connection and hitting it actually fixed it.... but i bought it into the warranty service center and got it fixed just to be sure.


Thanks.

[Tom41]

Re: Squealing LCD....?

Squealing in standby mode often indicates bad caps - they're trying to charge up, but are leaking (since they've vented) and causing a noise. My old VCR, with the bad PSU cap, made a little squeak when the mains was applied or removed. Also, the Kobian Mercury PSU (see the PSU Build Quality Pictorial thread) squealed in standby mode, because it had a vented cap.

I also have a laptop that could have a bad inverter. Occasionally the screen backlight will flicker and die, and the only way to get it back is to reboot the computer. Other times I see everything that's supposed to be black come out green, and I have seen a few times the display appear to 'melt away'! That is, the LCD itself suddenly loses power but the backlight stays on, so you see the pixels gradually fading to 'clear' again.

[gonzo0815]

Re: Squealing LCD....?

I have fixed an Acer TFT (wich now is Benq) and all i can say is, that the box is quiped with bad Lelon crap caps and ok some Nichicon for the cirticall parts in the SMPS. The CPU board is full of small SMD lytic`s, from wich i do not assume to be high quality. A few of them hase shown some bulging, but on this part iam not shure. I replaced a few, but as it is too risky with my current solder eqipment i cancled this. From what i have seen, the defekt`s on the newer Beq`s are from the similar type (except some crapy CCFL inverters) , e.g. i think they always are using bad crap caps in all of their products.

[kc8adu]

Re: Squealing LCD....?

squealing psu usually have bad caps.
the ripple they should filter out ends up showing up on the feedback.
hiss or squeal esp at light/no load is most always bad caps.

[stevo1210]

Re: Squealing LCD....?

Hello Everyone,

I haven't been back here for a while but yesterday I looked through the vents on the top of the BenQ FP937s and I saw some caps.... they had a brand called Elite or something like that (It wasn't very clear).
Could those caps be the culprit to the squealing noise.... The squealing part is getting worser through time.

The monitor is still under warranty but I just don't know what to tell the technicians down at the repair center.... last time I bought my Sony display there, It took them 3
times to get it fixed correctly *sigh*.


Thanks.