Anothother LCD problem.. Viewsonic VP140

[Michael Kennedy]

Hi everybody..

I came across another bad lcd monitor. It is a Viewsonic VP140 and I'm not
quite sure what its problem is..

It powers up and has a picture but it is really dingy and dark looking so I
figured that the backlight bulbs were probably going out. Well I took it
apart and check out the ccfl lamps and they appear to be burning as bright
as my other monitor's ccfl's... They aren't so bright that they are blinding
but they appar to be lit up pretty good.. Should they be as bright as a ccfl
in a scanner?

Another interesting problem is that the entire monitor shuts down after
running for a while. I've got no ideas on this one unless the bulbs are not
in spec or something and the inverter is shutting down and therefore the
whole monitor shuts down..

[Michael Kennedy]

hmmm.. the shutting down appears to be unrelated to the inverter because if
you power it up without the inverter it shuts down after a few seconds..
Just like it is doing with it plugged in..

Who knows what could be wrong with this thing... Somebody else was in here
before me and
"Michael Kennedy" <Mike...@remthis.comcast.net> wrote in message
news:HY6dne47bZM...@comcast.com...

[Caesar Valenti]

I have fixed 3 or 4 of these before....but not for quite a while. It
was always the same part and the same symptom.
The display would shut down after 10sec-3 min. Removing power
momentarily would make it work again.

It is due to a bad cap on a regulator (within the monitor; not the
separate pwr supply)
My memory is not great on this, so don't take my word on all the
details.....but....

I believe is was on a 5 volt supply; maybe -5v. I think it was on the
reverse side of the PC board; facing the LCD display.
I believe it was a 1 ufd cap.

I am not sure why it is dim, but none of these ever look very good....I
think the reflector gets tarnished (this is a guess!)

CV

[Michael Kennedy]

I'll change that cap out and see what happens..
Thanks for the info..

- Mike

"Caesar Valenti" <cae...@email.com> wrote in message
news:444f11c7$0$1491$742e...@news.sonic.net...

[Michael Kennedy]

Are you talking about an electrlytic capacitor because there are no
electrlytics on the back of the board..

- Mike

"Caesar Valenti" <cae...@email.com> wrote in message
news:444f11c7$0$1491$742e...@news.sonic.net...

[Caesar Valenti]

It was a surface mount part...probably not electrolytic.
I have one here that I fixed. I will take it apart to see the exact
part....assuming I can see which part it was that I soldered.
This may take a while.
Cv

[John Vallelunga]

Ok, this didn't take as long as I thought.

Keep in mind....I believe that they made at least 2 different versions
of this monitor; so beware. Mine was made in Feb '99 with a serial
number of AH90800764. The board number is 4141139001.

It looks like the part I replaced was an electrolytic (tantalum?) It
is on the reverse side of the board. It appears I replaced it with a
ceramic (non-electrolytic) cap. Since ceramic monoblock caps don't have
labels, I can't tell the value; but based on it's physical size, I would
guess either 0.1uf or 1.0 uf. Hopefully you can see the label on
yours. It is C135. While this is a surface mount part, you can probably
use anything that will fit.

As always, YMMV
Good Luck
cv

[Caesar Valenti]

Ok, this didn't take as long as I thought.

Keep in mind....I believe that they made at least 2 different versions
of this monitor; so beware. Mine was made in Feb '99 with a serial
number of AH90800764. The board number is 4141139001.

It looks like the part I replaced was an electrolytic (tantalum?) It
is on the reverse side of the board. It appears I replaced it with a
ceramic (non-electrolytic) cap. Since ceramic monoblock caps don't have
labels, I can't tell the value; but based on it's physical size, I would
guess either 0.1uf or 1.0 uf. Hopefully you can see the label on
yours. It is C135. While this is a surface mount part, you can probably
use anything that will fit.

As always, YMMV
Good Luck
cv

[Michael Kennedy]

Thanks... C135 is a 105 16v.. Is that 105uF?? pF? Sorry if that is a stupid
question but I'm still trying to learn. If this is an electrlytic it is not
one like I'm used to seeing.. It is a square yellow block that is about
1/8in thick.. I thought the aluminum cans were the only ones that are
electrolytics.

I learn something new every day.

- Mike

"Caesar Valenti" <cae...@email.com> wrote in message

news:44504d7b$0$1558$742e...@news.sonic.net...

[Caesar Valenti]

That would be "10" followed by "5" zeros or 1000000pf or 1,000,000 pf or
1 million pf . Pico is ^-12 while micro is ^-6.

1 million pf = 1 microfarad. I would go with a ceramic
(non-electrolytic) if you can find one small enough.
All the rest of mine are like yours....small yellow surface mount
blocks....those are all caps. The really small black ones are resistors.
Welcome to the world of miniature electronics!

CV