Viewsonic vp2130b & vx2235wm

[Blackstar]

Hello I have 2 viewsonic monitors that are having trouble vp2130b & vx2235wm. Since I registered on these great forums I thought I would make a post on what I'm doing.

vp2130b turns on and off repeatedly.
None of the caps physically look bad on any of the boards.
The power supply shuts off and turns back on when either back lights are plugged into the inverter board. Hopefully I didn't damage any other components when testing point of failure. The power supply board got hot and smelt small amount of burning from the transformer when the monitor was turning off and on repeatedly. I took caps off the inverter board too try to determine if they are bad. None of them seen horribly awful besides one that had a larger ESR then the others. Any input with this problem would be appreciated.

vx2235wm turns on then shuts off until it warms up.
Upon inspection of the vx2235wm power supply their are several bulging caps.

I just got my capacitor order from digikey so I will post back shortly with more information.

What is a good substance to hold down caps on a pcb board? I was thinking hotglue or silicon.

[R_J]

Re: Viewsonic vp2130b & vx2235wm

You do not have to glue them down, just solder them in place

[Blackstar]

Re: Viewsonic vp2130b & vx2235wm

Replaced the caps on the vx2235wm and it lives once again!

The transformer is bad on my vp2130b. Replaced all the caps on the inverter, power, and video board. I thought maybe the solder joints where bad so I removed the transformer and redid the solder joints on the pin header. There is little to no resistance on the secondary windings .05 ohms. The primary only has a slightly higher resistance. When the transformer is on it buzzes quite loudly. I can hear a moving part inside the transformer when I shake the board

I attached a short video of a 2 second black out vp2130b.zip or the link below.

<Link Removed>
What do you guys think?

Is it worth trying to find a new transformer or should I just buy another board? I can get one on eBay for $20.

[Agent24]

Re: Viewsonic vp2130b & vx2235wm

Sure it's not a shorted rectifier or other part on the secondary side? Main SMPS transformers hardly ever go bad. Inverter transformers on the other hand...

[budm]

Re: Viewsonic vp2130b & vx2235wm

Replaced the caps on the vx2235wm and it lives once again!

The transformer is bad on my vp2130b. Replaced all the caps on the inverter, power, and video board. I thought maybe the solder joints where bad so I removed the transformer and redid the solder joints on the pin header. There is little to no resistance on the secondary windings .05 ohms. The primary only has a slightly higher resistance. When the transformer is on it buzzes quite loudly. I can hear a moving part inside the transformer when I shake the board

I attached a short video of a 2 second black out vp2130b.zip or the link below.

<Link Removed>
What do you guys think?

Is it worth trying to find a new transformer or should I just buy another board? I can get one on eBay for $20.

Doubt that the transformer is bad, the DCR of the power transformer will be very low, you have to use inductor tester to test the inductance and the ringer for testing to see if it has shorted turn.
Transformer will have very high Inductive reactance when it is exposed to the high frequency switching Voltage which is used in the switching power supply. You use Ohm meter to verify if the winding is open or not.
2-second to black can be due to bad inverter circuits, bad lamps, bad power supply, bad inverter transformer.

[Agent24]

Re: Viewsonic vp2130b & vx2235wm

By the way the test in your video is not accurate. You have not connected all the lamps to the inverter. Then the inverter will think some lamps are bad (open circuit) and shutdown anyway.