Viewsonic VX910

[neumannu47]

Re: Viewsonic VX910

I'm now dealing with a VX910 with the same symptom. It was working fine until it stopped working. When I opened it up, there were several caps with bulging ends. The large cap, which does not normally fail, was not only bulging, one lead fell off when I touched it.

After replacing all of the electrolytic caps with low ESR 105 degree parts, the problem persists. I've started doing some probing on the power supply board, and it seems that the PWM chip is not starting up. The 10uF startup cap has been replaced twice, just for good measure. There is 171 volts across the big cap. The only activity on the board is a spike about once per second. It's hard to tell where it's coming from.

This is the first LCD monitor I've tackled. If I'd seen one working correctly, I'd have a better idea where to start. Thanks to SMITHWHO, I have the correct schematic. My best guess at this point is the PWM chip, U320. Thoughts?

[SMITHWHO]

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.

ADDRESS FOR SCHEMATIC SAME AS VX910

[donatdonlo]

Re: Viewsonic VX910

Hi all, I'm having the same issue as AJ above on a VX910. I replaced all the Crapxons ( I repaired one of these last week ) except the large one. I also replaced the Polypropylene cap in the pics shown previously. I also found a bad solder joint in one of the small blue ceramic caps and The monitor's green light comes on and every two seconds there's a light flicker at the bottom of the screen. I measured the resistance on the small surface mount transistors on the bottom side of the board. The top of my board in this area looks like it was cooked in an oven. The two SM transistors on the left as you're looking at the bottom of the board read 3 ohms from the middle pin to the top pin and 7 opens from the middle pin to the bottom pin. On the right side the readings are 3 ohms from middle to top and 18 ohms from middle to bottom. I'm guessing the two on the cooked side of the board are cooked as well. When I measure a brand new one of these out of circuit I get nothing from middle to top, and 18 ohms frrom middle to bottom.

[donatdonlo]

Re: Viewsonic VX910

The part # for the Polypropylene cap at DigiKey is P14242-ND, I just ordered 1 to replace a bad one on the same board. It had actually lead a molasses like matter from it. I replaced all the CrpXon's as well and I'm about to start meter reading.

[jetadm123]

Re: Viewsonic VX910

what are the transistors they are shorted dk qp not much help
pnp npn 5 v 50 v etc hope you can tell me
sincerly j.r. Smith

dk- 2sc4672

qp-production code

[budm]

Re: Viewsonic VX910

Which board does it use? FP035-1PI01?

[SMITHWHO]

Re: Viewsonic VX910

Monitor in question is viewsonic vx910 model #vs10167

[SMITHWHO]

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

what are the transistors they are shorted dk qp not much help
pnp npn 5 v 50 v etc hope you can tell me
sincerly j.r. Smith

[NAM]

Re: Viewsonic VX910

2SC4672

http://cgi.ebay.com/ws/eBayISAPI.dll...:X:AAQ:US:1123

I had the same problem with a Viewsonic VX724. Those transistors and the transformer on the other side were burnt.
You should test the transformer too.

I ended up just purchasing a whole new board from Ebay. $23, less screwing around.

[Nocta]

Re: Viewsonic VX910

2SC4672

http://cgi.ebay.com/ws/eBayISAPI.dll...:X:AAQ:US:1123

I had the same problem with a Viewsonic VX724. Those transistors and the transformer on the other side were burnt.
You should test the transformer too.

[NAM]

Re: Viewsonic VX910

Well... I hooked up an external 12v source. Worked great.... for about 5 seconds...then the two transistors on that side popped; the magic smoke escaped, and it was laid to rest.



time for a new monitor.

[NAM]

Re: Viewsonic VX910

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"..

So, I checked the voltage here, and it goes from around 4v, crawls up to 12v, then drops to 4v again. Is there a prime suspect in this case? I have replaced the caps, tested the other caps, no bad solder joints, no holes in the transformers, etc.

Side note: Is simply hooking this up to an external 12V supply a feasible workaround? Would one still need 120v to power the backlight?

Thanks for everything! Very useful information thus far!

[budm]

Re: Viewsonic VX910

Those two caps are for the ROYER oscillator Inverter output circuits tuning caps, you have to always check them for value and leakage resistance otherwise it will take out your new transistors, very common failure in DELL/BENQ/HP/VIEWSONIC monitors.

[ajsemtb]

Re: Viewsonic VX910

I don't know if you still have this monitor or power supply, but I just got an ESR meter, and I saved my caps from the repair knowing some day I would get one, and the 4 aluminum caps I replaced were all in tolerance and low ESR, so that was not my problem. I also replaced the red poly cap, the 2 little blue caps by the transformer, and the 2 transistors on the bottom of the board. Get a flux pen, its helps!

Transistors on bottom of board part # from digikey: http://www.digikey.com/product-searc...4672T100QCT-ND

I replaced these or at least 1 of them because I damaged it removing it... : http://www.digikey.com/scripts/DkSea...=0&y=0&cur=USD

These are the 2 ceramic caps, don't know if they were bad: http://www.digikey.com/scripts/DkSea...=0&y=0&cur=USD

And this was the red poly cap I installed: http://www.digikey.com/scripts/DkSea...=0&y=0&cur=USD

I hope this helps someone someday.

[nasjatt]

Re: Viewsonic VX910

What is wrong with the monitor?

For example, do you get a green power LED? Do you see the monitor flash on briefly?

The more info you give, the better help you will get.

The power light goes on/off fast and screen flashes with it
< little slower then this

[retiredcaps]

Re: Viewsonic VX910

I have replaced some caps already but still didn't work.

What is wrong with the monitor?

For example, do you get a green power LED? Do you see the monitor flash on briefly?

The more info you give, the better help you will get.

[nasjatt]

Re: Viewsonic VX910

Yeah, so I FIXED IT!!!!! With all y'alls help of course. I got my parts in and I don't know exactly what part fixed it, because I just decided to replace EVERYTHING, and didn't do tests in between... SO on this board, I replaced all the Aluminum Capacitors, the 2 ceramic blue caps by the transformer on the right side of the board, the 2 little transistors on the bottom of the board, the red poly cap on the top of the board (with one that was the same amounts, but it was bigger 15mm leads instead of 10mm leads, but I bent them to look like spongebob Square pants and legs and it fit fine... , resoldered the transformer, tested the MOSFET, tested the resistors at R112 and R320 by desoldering 1 leg and doing an ohm reading, all in tolerance. And now it works!!! All in all, less than $20 in parts and shipping, still cheaper than a new power supply!

SO my suggestion to anyone who has this board and will come on this thread in the future, change your caps (including the tiny startup cap, but not necessarily the huge one unless its bulging) replace the little blue caps right by the transformers, the red cap in front of the transformers marked 154, and replace the tiny transistors on the bottom of the board. Not really hard, just be careful with your soldering iron that you don't miss and hit something else... :/ And watch the videos on this thread about surface mount soldering. Thanks to RetiredCaps, PlainBill and everyone else that helped me with this repair!!!

Someday I'll get a capacitance meter and be able to figure out which of these caps actually failed... Yes, I will keep them until I can check them so I know... LOL

Attached is a pic of my "array" with it back in its place in the middle..

I am happy to your success and I am motivated to fix my 2 monitors now…
Is it possible that you can provide the part numbers and where you ordered them from?

I have replaced some caps already but still didn’t work. (See img)

Thanks for you help…

[Ken256]

Re: Viewsonic VX910

Good job on fixing your monitor. I have a Viewsonic VX710 that has the same power supply and it also had bad electrolytic caps. I've seen some debate on the forums about whether the big primary-side filter cap should be replaced. They do fail. The 100uF, 400V filter cap on my VX710 did fail. When I desoldered it from the board, I found that one of the legs was broken or burned off inside the capacitor case. That seemed extreme.

I also found the power supply controller chip had failed, probably because the main filter cap failed. The controller chip was a SG6841 surface mounted to the bottom of the board.

I think this design from Viewsonic has bad cooling. The heatsinks are too small and the case ventilation is poor. Bad solder joints develop, the circuit board gets discolored. I guess we've seen that in your pics.

[PlainBill]

Re: Viewsonic VX910

Yeah, so I FIXED IT!!!!! With all y'alls help of course. I got my parts in and I don't know exactly what part fixed it, because I just decided to replace EVERYTHING, and didn't do tests in between... SO on this board, I replaced all the Aluminum Capacitors, the 2 ceramic blue caps by the transformer on the right side of the board, the 2 little transistors on the bottom of the board, the red poly cap on the top of the board (with one that was the same amounts, but it was bigger 15mm leads instead of 10mm leads, but I bent them to look like spongebob Square pants and legs and it fit fine... , resoldered the transformer, tested the MOSFET, tested the resistors at R112 and R320 by desoldering 1 leg and doing an ohm reading, all in tolerance. And now it works!!! All in all, less than $20 in parts and shipping, still cheaper than a new power supply!

SO my suggestion to anyone who has this board and will come on this thread in the future, change your caps (including the tiny startup cap, but not necessarily the huge one unless its bulging) replace the little blue caps right by the transformers, the red cap in front of the transformers marked 154, and replace the tiny transistors on the bottom of the board. Not really hard, just be careful with your soldering iron that you don't miss and hit something else... :/ And watch the videos on this thread about surface mount soldering. Thanks to RetiredCaps, PlainBill and everyone else that helped me with this repair!!!

Someday I'll get a capacitance meter and be able to figure out which of these caps actually failed... Yes, I will keep them until I can check them so I know... LOL

Attached is a pic of my "array" with it back in its place in the middle..

All you need is two more and Halle Berry reading a book.

PlainBill

[ajsemtb]

Re: Viewsonic VX910

Yeah, so I FIXED IT!!!!! With all y'alls help of course. I got my parts in and I don't know exactly what part fixed it, because I just decided to replace EVERYTHING, and didn't do tests in between... SO on this board, I replaced all the Aluminum Capacitors, the 2 ceramic blue caps by the transformer on the right side of the board, the 2 little transistors on the bottom of the board, the red poly cap on the top of the board (with one that was the same amounts, but it was bigger 15mm leads instead of 10mm leads, but I bent them to look like spongebob Square pants and legs and it fit fine... , resoldered the transformer, tested the MOSFET, tested the resistors at R112 and R320 by desoldering 1 leg and doing an ohm reading, all in tolerance. And now it works!!! All in all, less than $20 in parts and shipping, still cheaper than a new power supply!

SO my suggestion to anyone who has this board and will come on this thread in the future, change your caps (including the tiny startup cap, but not necessarily the huge one unless its bulging) replace the little blue caps right by the transformers, the red cap in front of the transformers marked 154, and replace the tiny transistors on the bottom of the board. Not really hard, just be careful with your soldering iron that you don't miss and hit something else... :/ And watch the videos on this thread about surface mount soldering. Thanks to RetiredCaps, PlainBill and everyone else that helped me with this repair!!!

Someday I'll get a capacitance meter and be able to figure out which of these caps actually failed... Yes, I will keep them until I can check them so I know... LOL

Attached is a pic of my "array" with it back in its place in the middle..