Viewsonic VX2255WMB No Backlight/screen (With video link)

[Monument]

Hello,

I have a problem with Viewsonic VX2255 monitor, got it from my friend.
When I turn it on, the blue light lights up for 5 - 10 seconds, the screen flashes and I can see something on the screen with my flashlight. After 10seconds, it turns off. I've replaced the F200 fuse and one resistor. I've also browsed several threads about this monitor with no luck. Also, when it the monitor goes off ( red light) Then I can hear a buzzing sound.


Picture of the board :
http://www.upload.ee/image/3101551/DSC_0219.JPG


Video of the monitor:
http://www.youtube.com/watch?v=kL5oi...ature=youtu.be

[budm]

Re: Viewsonic VX2255WMB No Backlight/screen (With video link)

Please see this thread:
https://www.badcaps.net/forum/showth...087#post317087

Pictures of the top side of the board? Any bad caps with domed tops?

[Monument]

Re: Viewsonic VX2255WMB No Backlight/screen (With video link)

No, all the caps seemed to be alright to me, picture of the top side :

[Monument]

Re: Viewsonic VX2255WMB No Backlight/screen (With video link)

I tested the inverter circuit with an old CFL Lamp, here's how it acts:
http://www.youtube.com/watch?v=nQu7p...ature=youtu.be


What could cause this? Seems like a transformer? Or a capacitor?

[selldoor]

Re: Viewsonic VX2255WMB No Backlight/screen (With video link)

You need to try it with the test bulb in each socket one at a time. (three bulbs and the test)
In Fact first test is take out all the bulb connectors and connect one
at a time to see if one doesnt light at all.
Have you done a resistance test on the secondary windings on the inverter transformer

[Monument]

Re: Viewsonic VX2255WMB No Backlight/screen (With video link)

Tested all the four sockets, they all behave similar, lamp goes on/flashes for 1 second like on the video I posted before. How to test resistance of the transformer?

[selldoor]

Re: Viewsonic VX2255WMB No Backlight/screen (With video link)

did you use test bulb in all sequence - like this:

TB:B2:B3:B4
B1:TB:B3:B4
B1:B2:TB:B4
B1:B2:B3:T3

Secondary Resistance - You will need to get the Glue/Laquer off the
test points - Power OFF - Meter on Ohms 2000 test S1 to S2 and S3 to S4


I have also marked some solder joints in pink? It may be the picture but they look like they may need a reflow- try and remove the old solder and add fresh.- look for more with a magnifier.

[Monument]

Re: Viewsonic VX2255WMB No Backlight/screen (With video link)

No, I did not test the bulbs in the sequence You provided, I tested them one by one.
Secondly, the resistance of S1 to S2 is 607 ohms and S3 to S4 605 ohms.

[selldoor]

Re: Viewsonic VX2255WMB No Backlight/screen (With video link)

Transformer looks ok ie within 3%

[Monument]

Re: Viewsonic VX2255WMB No Backlight/screen (With video link)

What else to test/look? I don't want to give up, I want to give this monitor a life, but my knowledge is not enough so I could use some help for furter investigation.

[selldoor]

Re: Viewsonic VX2255WMB No Backlight/screen (With video link)

Can you test the bulbs using the sequence. I will read back through and see what to test.

[Monument]

Re: Viewsonic VX2255WMB No Backlight/screen (With video link)

Tested them using Your sequence, they look the same. I can hear some humming or buzzing sound when the blue light turns off.

Edit: Tried to change the big capacitor to see If it works, still same reaction.

[Monument]

Re: Viewsonic VX2255WMB No Backlight/screen (With video link)

I measured the resistance of the two big smd transistors behind the board, got readings from 300 ohms to infinite, does that mean the smd-s are open?

[selldoor]

Re: Viewsonic VX2255WMB No Backlight/screen (With video link)

OK - First test your small fuse again.
Next to test would be the fets on the back. 9973GH
See this thread for instructions - Read the whole thread
https://www.badcaps.net/forum/showth...ghlight=9973gh

Can you update your profile with country and mains voltage
EDIT
Haha you started without me

[Monument]

Re: Viewsonic VX2255WMB No Backlight/screen (With video link)

F101 : 0.3ohms
F200 : 1.3ohms (this fuse was blown, replaced it before I started this thread )

Country: Estonia
Voltage: 220V

[Monument]

Re: Viewsonic VX2255WMB No Backlight/screen (With video link)

Monitor is ALIVE!!! The problem was still with that F200 fuse, the one I replaced was still bad, so I replaced it again and now the monitor works!!!

Here's a picture :




Thank You all, especially selldoor, You guys here are awesome!!!

[selldoor]

Re: Viewsonic VX2255WMB No Backlight/screen (With video link)

Well done - wasnt sure about the last test you did on the fuse over 1 is a bit sus.

By the way - hate your offline pictures - took almost a minute to load this thread.

Perhaps there is time to delete the last one and post it using manage attachments
which is in Go advanced under quick reply (will have to be less than 2mb)

[Monument]

Re: Viewsonic VX2255WMB No Backlight/screen (With video link)

One weird thing about this monitor is that the resolution is weird, It should be 1680x1050, but It doesn't even have that option. It can be 1600x1200 or under 1440x1050 What to do? Or is the problem with analogue output?
Haven't tried DVI output as I don't have the connector.

[Monument]

Re: Viewsonic VX2255WMB No Backlight/screen (With video link)

All working, DVI outputs 1680x1050 just fine.

[tibimakai]

Re: Viewsonic VX2255WMB No Backlight/screen (With video link)

I have just repaired the same monitor, the difference is that Ihad two bulged 220uF/25V capacitors and the F200 fuse bad.
My question is about this fuse.
What is the difference between a 24V and a let's say 125V fuse? I have a 125V in there for now.