Wiewsonic VE710b black screen Flashing

[rogebe]

Re: Wiewsonic VE710b black screen Flashing

Hello budm,

You are right, the condenser C3 seems bad (the eye of master !)

For the yellow cap, I put it a which was between two good transistors.

Something else ?

Nice day to you.

RGB

[budm]

Re: Wiewsonic VE710b black screen Flashing

That bad filter cap C3 for the inverter power supply can cause the Royer Oscillator (the two C5707/5706, the tuning cap (0.22uf yellow cap), the inverter transformer) to run at the wrong frequency which will cause the transistors to run hot and burn up.
If I were you I will replace the electrolytic caps as a set, not just C3. Bad cap can look normal.

[rogebe]

Re: Wiewsonic VE710b black screen Flashing

Ok Budm,

I made a photo

In red the condensers which are before D108. It is a s à high voltage power rectifier. He has to feed both Royer Oscillator (inverters).

Transistors on the right was OK. Those on the left not

Normally caps in the red circle must be good

Rest C3 and C108 has to change

I am clear ?
It is right ?

Thank's for you answer.

RGB

[viziks]

Re: Wiewsonic VE710b black screen Flashing

Please also check 0.22uf condensers between the 2 C5707 transistors.Defective capacitor will cause transistors to overheat.
I hope you must have also checked and resoldered both inverter transformers near the transistors "100179 ".

[budm]

Re: Wiewsonic VE710b black screen Flashing

Post 20 also requested to check the capacitance of those two 0.22uf cap, but I am not sue if he did or not.

[rogebe]

Re: Wiewsonic VE710b black screen Flashing

Hello,

Before switch on the board I think resoldered both inverter transformers.

As I have two same boards (in fact, I have 4 same screens), I took transistors and yellow caps (0.22µf) which was good to replace on the other board.

But I am going to unsolder the yellow caps and to verify their value

However I do not see these transistors " 100179 " ?

The reflextion on the post 23 is right ?

C3 is very important for Royer Oscillator ?

What is the fonction of C108 ?

Thank you for you interest in my problem.

RGB

[rogebe]

Re: Wiewsonic VE710b black screen Flashing

I resoldered the two inverter transformers.

I measured the two yellow caps: 0.211 (scale 2uF).

I changed C3.

Good day for you.

RGB

[rogebe]

Re: Wiewsonic VE710b black screen Flashing

Hello guys,

I had no answer to my last questions.

Needs it to make the other thing ?

Thank's for you answers.

Good day.

RGB

[rogebe]

Re: Wiewsonic VE710b black screen Flashing

Up

[rogebe]

Re: Wiewsonic VE710b black screen Flashing

Hello,

I have to go back up the board and the screen works again.

Thanks to all those who gave me somme ideas to repair.

Finally I have to change two transistors (Q10 and Q11), C3, to check condensers yellow and to resolder transformers.

Well I have two similar screens to be repaired.

Coming up next.

Good day.

RGB

[rogebe]

Re: Wiewsonic VE710b black screen Flashing

Hello

I repaired an other one.

2 on 4 but I do not have transistors anymore to be cannibalized.

Still one thank you.

Nice day for you.

[Agent24]

Re: Wiewsonic VE710b black screen Flashing

I repaired an other one.

2 on 4 but I do not have transistors anymore to be cannibalized.

Did you have a look on eBay?