LCD 19" BENQ T905 problems

[capullaco]

Re: LCD 19" BENQ T905 problems

What retiredcaps is talking about are the 4 inverter tranformers. If you look at the first photo in post #26, they are the 4 small square yellow boxes on the left side of the photo. You should use desoldering braid to soak up the old solder from the transformer pins and then apply new solder. Do this for all 4 transformers.

Ok im gonna try. But do you think those fuckers are gaving those problems? The display started to stink when I turned it on

[jetadm123]

Re: LCD 19" BENQ T905 problems

Err...no
Which ones are the transformers? The box like ones?

What retiredcaps is talking about are the 4 inverter tranformers. If you look at the first photo in post #26, they are the 4 small square yellow boxes on the left side of the photo. You should use desoldering braid to soak up the old solder from the transformer pins and then apply new solder. Do this for all 4 transformers.

[capullaco]

Re: LCD 19" BENQ T905 problems

Err...no
Which ones are the transformers? The box like ones?

[retiredcaps]

Re: LCD 19" BENQ T905 problems

What can it be now?

Did you resolder all the transformer pins and other components as suggested in post #21?

[capullaco]

Re: LCD 19" BENQ T905 problems

Ok, after changing the blown transistors and fuse, and replacing all the Elite caps I tested the display.

It showed the BenQ logo!...but it just stayed for 2 secs, and it wasnt properly lighted, like if the brightness was low.
Between those 2 secs, there are some artifacts, like color inverted image,etc..

Also, the display started to stink a bit, so I disconnected it.

What can it be now?

[PlainBill]

Re: LCD 19" BENQ T905 problems

What is the value of the polyester caps?

Someone said, 220 nF 160V but I have read on another site that is 0,022 micro F.
Maybe the guy misspelled it and added a 0?

AFAIK 220nF = 0,22 micro F
On one side of the cap says " .22 160 " but is 0,22 pico? nano?
On top of the cap there is a "K".

One quick and easy way to get the answer to this is to go to a site such as Digikey or Mouser. Look up the physical size of .22 uF, 22nf and .22nF 160 volt caps. It becomes very easy to determine which is correct.

PlainBill

[capullaco]

Re: LCD 19" BENQ T905 problems

What is the value of the polyester caps?

Someone said, 220 nF 160V but I have read on another site that is 0,022 micro F.
Maybe the guy misspelled it and added a 0?

AFAIK 220nF = 0,22 micro F
On one side of the cap says " .22 160 " but is 0,22 pico? nano?
On top of the cap there is a "K".

[capullaco]

Re: LCD 19" BENQ T905 problems

If it looks in good order,ie. not swollen or split,then it is probably Ok,I have never seen one of these fail ....YET.Just ensure that you resolder the pins, because dy joints on these do happen regularly.

Shape seems OK, but it was between the 2 blown transistors, so I thought it could be blown also...

[retiredcaps]

Re: LCD 19" BENQ T905 problems

Ok,found another blown transistor.

Yes, that I is what I meant by fail in pairs.

I have marked them on the pic attached.

What type of capacitator is? Which mesure? Is there any way to test it with the multimeter?

http://en.wikipedia.org/wiki/File:Condensators.JPG

http://en.wikipedia.org/wiki/Capacitor#Capacitor_types

This picture is much better than the original. In the original, we could not see the entire board because of the angle.

That is why clear focused top down view pictures are so valuable.

[Rtech]

Re: LCD 19" BENQ T905 problems

If it looks in good order,ie. not swollen or split,then it is probably Ok,I have never seen one of these fail ....YET.Just ensure that you resolder the pins, because dy joints on these do happen regularly.

[capullaco]

Re: LCD 19" BENQ T905 problems

Ok,found another blown transistor.
I have marked them on the pic attached.

Between them there is a gray box called C826
Is like the 2nd pic attached.

It has a "K" on top, and on one of the sides reads:

R75 MP
.22 160
T2 05MLK13

What type of capacitator is? Which mesure? Is there any way to test it with the multimeter?

[capullaco]

Re: LCD 19" BENQ T905 problems

The diodes are ok

Really,thanks a lot retiredcaps,not only youre helping me,but im learning a lot.
Again,thanks.

[capullaco]

Re: LCD 19" BENQ T905 problems

In pairs? What do you mean? The others seem ok,which other should I replace?

[retiredcaps]

Re: LCD 19" BENQ T905 problems

So far seems that all the transistors are ok but one.

Also I just notice there are some coil like things named also with "L". All those "L" things (what does the "L" mean?) Show 0,1 - 0,2 ohms
.
Im still not sure how to mesure diodes.

Always replace transistors in pairs.

Sorry, I made a typo above L = inductor, not I. To measure diodes see this youtube video.

http://www.youtube.com/watch?v=hRKzZ...eature=related

In fact, you can search youtube for "multimeter tutorial".

[capullaco]

Re: LCD 19" BENQ T905 problems

So far seems that all the transistors are ok but one.

Also I just notice there are some coil like things named also with "L". All those "L" things (what does the "L" mean?) Show 0,1 - 0,2 ohms
.
Im still not sure how to mesure diodes.

[capullaco]

Re: LCD 19" BENQ T905 problems

Test them with your diode setting. One way should measure 0.4 to 0.7V. Reserve and the other way should measure "1" or 0L.

Which one is the diode setting?
Can it be the the arrow one? -->| with a music note? Or one called "hFE" ?

This Benq board is widely known to have the problems mentioned in post #20 and #21. If you read or search for Benq here, you will see the same things to check and preventative recommendations over and over.

The problem is that I dont know what is what. The transformers are those squares with white/yellow tape over them?

Cant upload proper images, because I dont have my good camera,only this old one without macro mode.And my mobile phone is broken :<

[retiredcaps]

Re: LCD 19" BENQ T905 problems

btw,the blown fuse means that theres some other thing blowed also,because of that?

Fuses can go bad just by themselves. But they blow for a reason. It is likely that one of your transistors is shorted or the transformers are poorly soldered. Hence the recommendations on post #21.

This Benq board is widely known to have the problems mentioned in post #20 and #21. If you read or search for Benq here, you will see the same things to check and preventative recommendations over and over.

[retiredcaps]

Re: LCD 19" BENQ T905 problems

1- Some of them have a numeration starting with "L", ex: L605 . Those seem to be ok (values 0.1 , 0.2)
2- The other ones I think they arent fuses, they start with "D", the numbers on them are far more visible and go out of range.

F = Fuse
I = Inductor (they should measure around 0.2 ohms)
D = Diodes

Test them with your diode setting. One way should measure 0.4 to 0.7V. Reserve and the other way should measure "1" or 0L.

[capullaco]

Re: LCD 19" BENQ T905 problems

The showing of 197 is your multimeter not reacting fast enough. For your own fun and learning, try testing the same transistor on the 2k, 20k, and 200k scale and see what you get.

Where I said one second, it really was a tenth part , barely got time to see it

Tried it with 200k and showed high numbers, so guess that it has a lot more resistance

Edit:

btw,the blown fuse means that theres also some other thing blowed,because of that? I think that fuses are meant to protect those kind of things, but im asking just in cause. Or maybe a better question would be, what caused the fuse to blow.

[capullaco]

Re: LCD 19" BENQ T905 problems

Ok checked the other "fuses". At least they seem like fuses but:

1- Some of them have a numeration starting with "L", ex: L605 . Those seem to be ok (values 0.1 , 0.2)
2- The other ones I think they arent fuses, they start with "D", the numbers on them are far more visible and go out of range.