VX2255wmb will not powerup

[fennec]

Hi,

I got a dead VX2255wmb from work. It received a snowball and it seems fuses are dead. My multimeter is dying, I ordered a new battery. I can check for continuity but it will power down if I try to check ohms values.

I changed a SMD fuse at the back of the PSU card but it still didn't powered up. I found an other fuse on the front, I think it's the one referred as F103 on the card but I scratched the writing while removing the glue.

It seems the main fuse is a regular resistor but I'm not sure I read the rating correctly, 10 ohms +/- 20% (second picture), is it equivalent to the spare on I found (first picture) ?

Thx for your help !

[budm]

Re: VX2255wmb will not powerup

The first picture shows Brown Black Black Gold = 10 Ohms 5%
The second picture shows Brown Black Brown Gold = 100 Ohms 5% unless the color in the picture is not clear.
I never use fusible resistor larger than 10 Ohms.
Can you please show good picture of the bottom side?
There should be a soldered in main AC fuse close to the AC inlet, I think it is the small rectangular box on the left of the AC inlet.
You should also Ohm out the MOSFET mounted on the heatsink close to that fuse you taken out.

[fennec]

Re: VX2255wmb will not powerup

Hi budm,

The first picture is the spare resistor I have, colors are indeed Brown Black Black Gold Brown ( 1 0 0 * 0.1 = 10 ?).
The second picture is the fuse I removed, colors are Brown Black Brown Gold Black (1 0 1 * 0.1 = 10.1 ?). The other side of the resistor is very damaged, the colors can only be seen on this angle.

I forgot to tell that I checked the fuse next to main, it is OK. When I plugged the monitor to check, the big capacitor was charged.

I checked the MOSFET, I read 700 between Gate and Drain, is it enough ?

Thx for your quick reply !

[budm]

Re: VX2255wmb will not powerup

Unless the resistors are 1% type, it does have 5 color bands, but it looks like MOX fusible resistor type. Please see Resistor color code.
You need to check S ource and Drain.
We need to bottom side of the board so we can see ho that burnt out resistor is connected. Is the resistor connected to the Source and Negative lead of the Main DC filter cap? If it is, then more likely to be 10 Ohms resistor 1% type.

[fennec]

Re: VX2255wmb will not powerup

I thought it was different reading since both resistors are 5 and and not 4 bands.

I checked Source and Drain also, it was around 700 ohms. Only Gate and Source was "short".

I'll post a picture of the back this evening when I'll be back from work.

Thx !

[budm]

Re: VX2255wmb will not powerup

I would check the MOSFET out off the board, 700 Ohms does not sound right al all, but dead short Gate and Source? You may be reading the shorts in the output section of the IC that drive the Gate also. Remove the MOSTFET and measure the Gate connections to Source to see if it read shorts or real low Ohm.

[fennec]

Re: VX2255wmb will not powerup

Those readings might be because of the dying battery of my multimeter, I'll unsolder it this evening and do the readings.