fp767 loud sizzle sound when get signal??

[murcielagotr]

im newbie here, and im not experienced a lot at electronic, i googled and find this cool forum

my monitor still living for now but im sure its giving a warning signal to me. yesterday i started my computer and after vga signal came my benq monitor start to sizzle continous and very loud, its sounds like little sparks jumps from edge to edge inside monitor case, so i scared and shutdown. Also i noticed when screen goes dark (loating at windows) noise is very low..

restart to understand whats going on, monitors working correctly but sick noise never stops and when powerdown from its button noise is very low but when it shows someting its very loud and scarry, so i opened monitor's case

after removing plastic and metal case i run it to see where is this sound coming and voila: big transformer ( sticker says :19.20273.011 LTSJ), there are 4 small of them but they dont produce sound.

i look carefully to capacitor's top to see any defect, all seems ok to me..

what can be the defect part??
any suggestions???

if i can find a good camera i will take a macro picture...

[smason]

Re: fp767 loud sizzle sound when get signal??

Have you looked at the solder joints on the bottom of the transformer? (assuming it's on the board)

[murcielagotr]

Re: fp767 loud sizzle sound when get signal??

Have you looked at the solder joints on the bottom of the transformer? (assuming it's on the board)

yes i applied a little heat to see solder in joints change to liquid and leave to cooldown, but i dont have solder, do i need to add solder too??

[murcielagotr]

Re: fp767 loud sizzle sound when get signal??

yes i applied a little heat to see solder in joints change to liquid and leave to cooldown, but i dont have solder, do i need to add solder too??

there is no change after applying heat to transistors solder joints

and here is the pictures of board. Any suggestions??

[PlainBill]

Re: fp767 loud sizzle sound when get signal??

there is no change after applying heat to transistors solder joints

and here is the pictures of board. Any suggestions??

1. What is the history of this monitor? It looks like some caps are original and some may have been changed.
2. There are two possibilities - some physical change may have occurred in the transformer (in which case the noise may be annoying but is probably not harmful); or some electrical change has occurred on the board or on the logic board.
3. By your description of the noise, it is load related. That certainly suggests an electrical change - most likely a cap failing.
4. What is the brand and series of the light green caps? The black caps with the red dot on top?

PlainBill

[murcielagotr]

Re: fp767 loud sizzle sound when get signal??

1- im using monitor since 2005 without any problem. it doesnt see service before.(i hope i didnt buy a refurbished item from store)

4- light green caps brand lelon or pelon, 1000uf 10v(a423 m), 33uf 50v a414m, 1uf 50v 419 m,

black caps brand elite, and yes there are red dots on i dunno why: 470uf 35v - c 0424

3- is this transformer can be found easily? it have 10 legs..???

[murcielagotr]

Re: fp767 loud sizzle sound when get signal??

ok i went crazy with sound and removed the big transformer, i saw a little black plastic melt on its 5 legs 1 side of it. but it wast a big deal, plastic doesnt lose its shape but its surface there are tiny tiny bubles...

is it possible the over heat of transformer, melts its copper inside to make annoying sound?
if faulty part is transformer anyone know how to find spare part?? i mean whats voltage, current etc.. 4 transformer???

[PlainBill]

Re: fp767 loud sizzle sound when get signal??

1- im using monitor since 2005 without any problem. it doesnt see service before.(i hope i didnt buy a refurbished item from store)

4- light green caps brand lelon or pelon, 1000uf 10v(a423 m), 33uf 50v a414m, 1uf 50v 419 m,

black caps brand elite, and yes there are red dots on i dunno why: 470uf 35v - c 0424

3- is this transformer can be found easily? it have 10 legs..???

I see two possible approaches.
1. Neither Lelon nor Elite caps are noted for their quality. When a cap bulges, it is certain that it is bad. However, caps can fail without any obvious sign. Replacing all the electrolytic caps in the power supply and inverter sections would cost under $10 if you are in the USA.
2. Benq supplies monitors to Dell. Other than the audio amplifier, that board looks exactly like power supply / inverter for a Dell E172FPb or E173FPb. The odds are very good that the transformer from a defunct Dell board would be an exact replacement.

Personally, I would replace the caps first, but that's your choice.

PlainBill

[murcielagotr]

Re: fp767 loud sizzle sound when get signal??

thx for answer
i will try replace caps, i need to search local dealers first....

by the way, what happens if i use my monitor during finding caps??

[PlainBill]

Re: fp767 loud sizzle sound when get signal??

thx for answer
i will try replace caps, i need to search local dealers first....

by the way, what happens if i use my monitor during finding caps??

Don't try to buy replacement caps from just any source. You need special low-ESR caps. Note this list for recommended brands and series of caps. Here is a list of vendors in various countries. For the USA, I recommend Digikey and their First Class Mail shipping option.

As far as using the monitor - if you must, you must. Stop if you feel the noise is going to drive you insane.

PlainBill

[murcielagotr]

Re: fp767 loud sizzle sound when get signal??

thx a lot

[murcielagotr]

Re: fp767 loud sizzle sound when get signal??

i dont give up and try to use it again and get mad cos of sound.

And again i try to check components. This time leak was visible. I m sure it wasnt like this last time.

Problem was biggest cap ( 450v 120μf 18mm diameter, 48mm height) i replaced it and VOILA

its now super silient

@plainbill
i cant find quality caps you mentioned in my city, also finding 120μf 450v from any firm was very hard. they recommend me 400v 120μf but i didnt want to buy.
i checked 12 store and found 1 (it was elite like old one) thx for your help.

its strange that 1 cap have problem and cos of it transformer generate to much buzz.

[PlainBill]

Re: fp767 loud sizzle sound when get signal??

i dont give up and try to use it again and get mad cos of sound.

And again i try to check components. This time leak was visible. I m sure it wasnt like this last time.

Problem was biggest cap ( 450v 120μf 18mm diameter, 48mm height) i replaced it and VOILA

its now super silient

@plainbill
i cant find quality caps you mentioned in my city, also finding 120μf 450v from any firm was very hard. they recommend me 400v 120μf but i didnt want to buy.
i checked 12 store and found 1 (it was elite like old one) thx for your help.

its strange that 1 cap have problem and cos of it transformer generate to much buzz.

Congratulations for fixing the monitor.

The transformer noise is not surprising. Because the 'mains filter cap' cap was bad, the input voltage to the power FET varied greatly. That meant that at times the SMPS transformer primary had to handle much higher current.

PlainBill