Viewsonic ve710b question

[duceolsen]

Hello all, figured I would post my question on here to see if anyone could help.

I have several ve710b monitors I have been working on and have come across 3 different power/inverter designs.
The attached schematic and image are for the version that I have been able to successfully repair just by replacing the circled (red) capacitors.

The problem I am having is with a version that has removed the items circled (blue) and several of the capacitors have different ratings.
After replacing all the same caps on this board with new the monitor has the backlight 2 sec on then off problem. This occurs with every monitor that has this board version. I have verified that the cffl lights are good.

Something I have found by accident is that by removing the circled (green) cap the monitor works fine.

any ideas?

[PlainBill]

Re: Viewsonic ve710b question

Hello all, figured I would post my question on here to see if anyone could help.

I have several ve710b monitors I have been working on and have come across 3 different power/inverter designs.
The attached schematic and image are for the version that I have been able to successfully repair just by replacing the circled (red) capacitors.

The problem I am having is with a version that has removed the items circled (blue) and several of the capacitors have different ratings.
After replacing all the same caps on this board with new the monitor has the backlight 2 sec on then off problem. This occurs with every monitor that has this board version. I have verified that the cffl lights are good.

Something I have found by accident is that by removing the circled (green) cap the monitor works fine.

any ideas?

A suggestion: Label the components you have circled with their identifier number (the cap circled in green is C823, for example). This way we can correlate the components in the picture with the schematic.

PlainBill

[duceolsen]

Re: Viewsonic ve710b question

The picture and schematic are not exact with the board I am having trouble with. The board I am having problems with is a newer version and I am unable to find any information online for it.

On the board I am having issues with.
C823- is 470uf 25v
C825- is 470uf 16v
C828- is 1000uf
C824- is removed

I will take a picture of the board I am having issues with and upload it tonight

[duceolsen]

Re: Viewsonic ve710b question

images of front and rear of board
This board says va721 on it, but is out of a ve710b monitor.

I have found that every ve710b monitor that was manufactured in July of 2005 has this board in it.
Notice the really large replacement cap , I acquired a large bag of nichicon 1000uf 25v capacitors and have not gotten around to buying smaller ones.

[duceolsen]

Re: Viewsonic ve710b question

I am getting 6v-7v and 14v-17v with C823 on and off the board.

[duceolsen]

Re: Viewsonic ve710b question

So could someone tell me, is it ok to run without the 470uf 25v capacitor?

Or what could be causing it to kick the backlights off after two seconds.