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Old 09-02-2010, 11:40 PM   #57
Badcaps Veteran
Join Date: Apr 2010
City & State: Canada
Posts: 9,162
Default Re: LCD 19" BENQ T905 problems

Originally Posted by capullaco View Post
1. Those are the transistors that were originally blown.Theyre blow again (the left arrow actually indicates the trans,not the cap :p)
Yes, because you chose to ignore 3 people telling you 4 times to resolder the transformers. This problem with the Benqs has been known for about 2 years now. When people say you *must* resolder the transformer it is because they have experienced what you have.

We can lead a horse to water ...

Here is the technical explanation why the transistors short out.

A poor analog might be the following (I can see PlainBill shuddering right now). Imagine a car engine as the transformer. When the bolts holding down the engine are loose, it shakes all the components of car.

You take the car to the mechanic (Eric the car guy). Eric says I can fix the loose radio, loose hoses, loose steering wheel, etc from all the damaged caused by the engine for $500.

Eric also HIGHLY recommends that he rebolts and remounts the engine. It will cost $1000. You balk. 2 days later, the engine causes the same damage. This time Eric charges you $1000 because the engine caused more damage than the first time.

Eric again recommends remounting and rebolting the engine, but this time it is $1500 because of more damage. You balk again.

And so on ...

Im not sure if they should be bridged... One is a pin of the 'K' cap of the 1st pic and the other one is a SMD named "JR10"
If you follow the circuit green pcb trace you should be able to tell if they are on the same circuit path or not. If they are, then it is not a problem if they are bridged.

I started here on these forums back in April 2010, but I can't remember a single case where a bridged connection has been documented as a problem.

I asked a similar question. See

4.I tried to compare those bridged with the image posted here, but im not sure, so I marked them
That is a good idea, but be aware that there are possibly many revisions of this board. Manufacturers can change the boards as they see fit.

5.Two new blown transistors.I dont know if they were blow before, but theyre now.
The picture's angle makes it hard to see, but those are probably dual diodes? They should have 2 diode symbols pointed towards the center.

What measurements did you get for these dual diodes?

6.Those are the things I have to resolder right? Are they marked correctly? What are those two things marked as '?' ? Should I resolder them also?
Yes, resolder those. L indicate an inductor. T is a transformer.

7.Finally, this is the bit I said it was burnt.but the transistor under it its fine.
Some browning is normal. As long as the transistor underneath tests okay, it is fine.
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