Viewsonic VX910

[ajsemtb]

Re: Viewsonic VX910

Can I chime in on this thread? I have this same monitor, same issue, and my power supply board looks the same as well, with the same "burned" inverter on the right. If you look back at the very first picture he posted, the "white Box" on the right side has dark discoloration around it, and then the back picture on the left (where the white box now is) has a "circle" area of what appears to be a burned area. Mine looks just like that, and also on this forum somewhere I read that to test the ohms at the diodes on either side and you should get 750 ohms on boths sides, and if not, then one is probably failed. I did that test and I got 745ohms on one side, and 9 ohms on the other. The burned one, obviously game me the 9 ohm load. SO, none of my caps looked bulged at all, which I was disappointed to see, (hoping for an obvious quick fix) so, do the transisters sound like they would be the problem?

And OSE, did your repair work?

[Scenic]

Re: Viewsonic VX910

as for the caps on the powersupply/inverter combo board, 16V caps will do just fine, as there's only 12V coming from the PSU..

they usually have 25V 470uF CapXons (crapxons) in there for some reason..
they get cooked to death in those monitors as they're pretty hot-running..

my own one is polymerized (16V 470uF nippon chemicon), allthough thats pretty much overkill..

good luck

[OSE]

Re: Viewsonic VX910

Thanks for the help, ordered the transistors and hopefully will be able to report a successful repair.

[Scenic]

Re: Viewsonic VX910

Check the transformers, capacitors, etc. The service manual for a Belinea 101910 fits this monitor.

PlainBill

now that you say it, i remember where i've seen those insides.. in my own Belinea 101910

caps are the primary suspect.

if you have an external 12V power supply with at least 1.5A, you could try to hook it up to the powersupplie's output pins while it's connected up.

sort of like this (notice the 2 wires going into the connector between the PSU and controller board)


that way the monitor should turn on.. easiest way to test if the inverter part of the powersupply and LCD controller board are OK.

i think the pins were labeled. if not, follow the traces from the pins to the cap right next to that pin header (on the power supply board!) which connects both boards. that's your "12V injection point"..

[PlainBill]

Re: Viewsonic VX910

I numbered the pins from the bottom to the top like I have below.

-3
-2
-1


For the transistor on the far left of the picture I got the following readings

1-2, 16.8
1-3, 8.9
2-3, 25.2

The next transistor ( second from the left) gave me these readings

1-2, 25.4
1-3, 9.1
2-3, 16.9

The two transistors on the right side of the picture do not produce a reading when connected from pins 1-2 and 1-3. They do however produce a reading of 168 Ohms when connected at pins 2-3.

I have attached a picture of my meter in case I may have a setting incorrect. Better to get something like that sorted out now rather than later.

Good idea posting the picture. You did the measurements properly. That 9 ohms sounds a little high, but the comparison to the other side indicates there is a problem.

If these transistors are the ones I expect, they should have the letters DK on one end, and Qx on the other (x can be any letter; on mine it was H). The actual part number is Rohm 2SC4672 and they are available from both Digikey and Mouser for about $.75 each.

Check the transformers, capacitors, etc. The service manual for a Belinea 101910 fits this monitor.

PlainBill

[OSE]

Re: Viewsonic VX910

I numbered the pins from the bottom to the top like I have below.

-3
-2
-1


For the transistor on the far left of the picture I got the following readings

1-2, 16.8
1-3, 8.9
2-3, 25.2

The next transistor ( second from the left) gave me these readings

1-2, 25.4
1-3, 9.1
2-3, 16.9

The two transistors on the right side of the picture do not produce a reading when connected from pins 1-2 and 1-3. They do however produce a reading of 168 Ohms when connected at pins 2-3.

I have attached a picture of my meter in case I may have a setting incorrect. Better to get something like that sorted out now rather than later.

[PlainBill]

Re: Viewsonic VX910

Is it ok to test the transistors while still on the board? I had done some initial testing after getting your reply and the readings I was getting were rather odd. It seemed like however I placed the leads on my meter I always got a reading from it.

OK, a newbie. We can handle that.

Yes, you can test the transistors without removing them. Here is the procedure I use:

Set the DMM to the lowest ohms ohms range - typically 200 ohms.

There are three pins on these transistors (in the picture above, the pin at the left connects to the middle pin on the right). Numbering the pins on the right 1 - 3, measure the resistance 1 to 2, 1 to 3, and 2 to 3.

PlainBill

[OSE]

Re: Viewsonic VX910

Not an exact match for the symptoms I am seeing, but check the transistors I have circled to see if they are shorted.

PlainBill

Is it ok to test the transistors while still on the board? I had done some initial testing after getting your reply and the readings I was getting were rather odd. It seemed like however I placed the leads on my meter I always got a reading from it.

[OSE]

Re: Viewsonic VX910

[PlainBill]

Re: Viewsonic VX910

Not an exact match for the symptoms I am seeing, but check the transistors I have circled to see if they are shorted.

PlainBill

[Dgtech]

Re: Viewsonic VX910

I'd like to beleive that all problems come from the power board however this is not true. There is a digital processing board that is in this monitor also. Whenever possible, post a pic of it (front/back) also.

What type and values are the caps on the power board?

[OSE]

Re: Viewsonic VX910

[PlainBill]

Re: Viewsonic VX910

I am having a power problem with my VX910. The green light on the power button will light up however the screen remains blank. After a few seconds the screen will give an image for maybe 1 second. Once that image appears it quickly vanishes and the monitor power cycle through this process repeatedly.

From what I've been reading online these monitors seem to have quite a few issues with bad caps and other power issues however I don't know which parts should be replaced.

All the bad ones.

Open up the case, post pictures of the power supply board - top and bottom. (Note the link to the proper procedure for posting pictures in my signature.)

PlainBill

[OSE]

I am having a power problem with my VX910. The green light on the power button will light up however the screen remains blank. After a few seconds the screen will give an image for maybe 1 second. Once that image appears it quickly vanishes and the monitor power cycle through this process repeatedly.

From what I've been reading online these monitors seem to have quite a few issues with bad caps and other power issues however I don't know which parts should be replaced.