Problem with Viewsonic VG920 lcd monitor

[PlainBill]

Re: Problem with Viewsonic VG920 lcd monitor

Noob. Cant believe Iv never found this site befor. I wanted to toss this out there. Alot of similar pieces. Im working with a Viewsonic IBM 17in monitor. We have several in shop all doing the same thing. You power it on only to have a blinking green front LED and a brief flash of the "viewsonic" screen saver. Acting like its not getting good power. I have to pinpointed to the power board but for the life of me cant seem to find out what. Iv tested every component along with many others in my shop. We bought a new monitor off ebay to compare, only to find a revision in the new board that makes it non-compatable with the video board. The P/N of the bad powerboard we have is 715G1492-J. The unit we bought offline has a powerboard of 715G1492-1. If anyone has some information I could try it would be greatly appreciated. The google machine seems to point me twards a few places online to pickup new ones for not to much but would rather try and fix what I got.

ninja edit***
There is an obvious heat mark in the center of the board. No swollen caps. Nothing blown off. I have done a basic reflow with no luck.

My first reactions: A lot of typing for very little information given. The pictures do little to help, flash reflection and small size make it difficult to see anything.

Points to check:

1. Power supply outputs. I would assume you have checked them, but would like some verification.
2. Status of the backlight control signal. Do the backlights go off, or are they switched off from the logic card (video board)?
3. Flashing power LED sometimes indicates a corrupted EEPROM.
4. Scorch marks in inverter area are common.

PlainBill

[mrpd]

Re: Problem with Viewsonic VG920 lcd monitor

Hey Plainbill This is MrPD sorry I haven't been back I got really busy with family and such but I just came across this again and I know this is really kind of old now but I am still willing to try to get this monitor back up so what do you think of what 12ax7a and Moam did?

yes, i can tell you first hand that after going through a bunch of these repairs last fall that the supervisory cpu reset chip causes more problems than they're worth. when they fail (and they seem to fail easily - possibly a bad batch and / or possibly a misunderstood design) they end up holding the graphics cpu in 'eternal' reset. the schematic for these monitors would indicate that acer's june grad engineers got confused over the meaning of logic active low / high.. or someone was just sleeping on the job when they 'designed' the 'enhanced' reset. originally this just appeared somewhere as a simple r/c delay for a smooth power up but then it looks like someone got the bright idea to incorporate a 50 cent part to destroy 1000s of monitors all over america. the fact is this pin can almost be left floating and still work just fine as evidenced by the picture attached. once removed or a couple pins lifted, these monitors are fine & i have yet to witness any problems related to unstable cpu initialization or anything else that would otherwise latch up the chip on startup. acer will tell you they've never heard of this & that you're the first to call of the problem... yeah sure.. i can't even imagine how many of these units just ended up in landfills across the planet... ~

AND

Guys, I had the same problem, viewsonic VG920 LCD monitor screen wont turn on.
After some reading, I did what 12ax7a suggested and took the Transistor U406
off the board. Also looking under the miscroscope I found U406 to be burnt out.

After putting everything back to gether and powered on the monitor, everything worked fine.

would this be something you would recommend that I should try? By the way Moam & 12ax7a if your still watching how are your monitors running?

Thanks,

[PlainBill]

Re: Problem with Viewsonic VG920 lcd monitor

Hey Plainbill This is MrPD sorry I haven't been back I got really busy with family and such but I just came across this again and I know this is really kind of old now but I am still willing to try to get this monitor back up so what do you think of what 12ax7a and Moam did?



AND




would this be something you would recommend that I should try? By the way Moam & 12ax7a if your still watching how are your monitors running?

Thanks,

The comments I made above still apply, with some modifications. I feel removing the reset controller is a valid way of troubleshooting. If it works you've identified the cause of the problem. Without KNOWING what is going on in the video processor IC I would be reluctant to turn it over to a customer without replacing the reset controller.

Here is the problem. In an ideal world a designer will evaluate a new generation of video processor carefully, noting all changes, and optomizing the current design to take advantage of the changes. I have noticed we don't live in a perfect world. It is entirely possible the new chip incorporated the reset controller and the designer missed that. Or somewhere in the process the BOM failed to get updated. OR any of the hundreds of things that can go wrong when the boss wants the work done yesterday.

In the final analysis, I would suggest you remove the reset controller and see if the monitor works. If t does, you have a choice. You could reassemble it and use it (or even sell it) without replacing the reset controller. The only down side as far as I am concerned is the effect of leaving the input pin floating. If you measure the voltage on it and it is at either of the power supply rails (3.3V or 0V I think) there should be no problem. If it's floating at around 1.6 volts, I would definitely install a new reset controller.

PlainBill

[mrpd]

Re: Problem with Viewsonic VG920 lcd monitor

Thanks for still looking at the older thread PlainBill!!

This LCD has never been or never will be for sale it is mine. It is one that I have lying around that didn't work, I would rather try and fix it and maybe use it for something like an LCD for building or trouble shooting computers then just throw it away if it is something as simple and small as this. I would never sell this LCD in the condition it is in or would be in, for sure. My concern is could anything burn up (or cause a fire) by leaving the reset controller off? Again that is presuming that this is my problem in the first place. Second I would like to put a new reset controller back on, in this matter I am wth you, if the designers put it there I think they did it for a reason, so do you know where to get the one I would need?

Thank a bunch for all your time and of cource all your help!!

PD

[jetadm123]

Re: Problem with Viewsonic VG920 lcd monitor

Thanks for still looking at the older thread PlainBill!!

This LCD has never been or never will be for sale it is mine. It is one that I have lying around that didn't work, I would rather try and fix it and maybe use it for something like an LCD for building or trouble shooting computers then just throw it away if it is something as simple and small as this. I would never sell this LCD in the condition it is in or would be in, for sure. My concern is could anything burn up (or cause a fire) by leaving the reset controller off? Again that is presuming that this is my problem in the first place. Second I would like to put a new reset controller back on, in this matter I am wth you, if the designers put it there I think they did it for a reason, so do you know where to get the one I would need?

Thank a bunch for all your time and of cource all your help!!

PD

Your answer is on post #29 of this thread. Why take a chance? The part cost is under $1.00 through digikey.com.

[mrpd]

Re: Problem with Viewsonic VG920 lcd monitor

Your answer is on post #29 of this thread. Why take a chance? The part cost is under $1.00 through digikey.com.

I agree but you know I couldn't find it on digikey I looked, I did a search and put in the part numbers but no luck. Maybe it is just me but do you maybe got a link for it on digikey?

Thanks,

[PlainBill]

Re: Problem with Viewsonic VG920 lcd monitor

I agree but you know I couldn't find it on digikey I looked, I did a search and put in the part numbers but no luck. Maybe it is just me but do you maybe got a link for it on digikey?

Thanks,

The things I have to do for my craft. The part is MAX810MTRGOSCT-ND; you can search for it on Digikey. The number in the other thread had Gee-Zero-Ess; the actual part number contains Gee-Oh-Ess.

PlainBill

[mrpd]

Re: Problem with Viewsonic VG920 lcd monitor

Plainbill-

Thankyou for that part number I found the reset controller. I do have another issue though. From the other posts

The comments I made above still apply, with some modifications. I feel removing the reset controller is a valid way of troubleshooting. If it works you've identified the cause of the problem.
In the final analysis, I would suggest you remove the reset controller and see if the monitor works.
PlainBill

I did take off the reset controller to verify that this is the problem and guess what? It was, but I have another issue now. Although it did turn on and I saw the viewsonic screen. I shut it off using the button I put it back together (plastic housing ect) it now will not turn on, again. I have no green light no screen at all. So what do you think might have happened now? I went ahead and redid all of the trouble shooting suggestions you gave and everything was the basically the same

large cap was 160 (meaning the fuse OK also right?)

voltage from the power supply wires:

Black
0.00

Brown
4.47

Red
14.47

Orange
0.00

Yellow
4.95

Green
4.95

Blue
0.00

Purple
0.00

Voltage Regulator
Starting from the top voltage regulator :
Left - 3.29
Middle - 2.46
Right - 2.64

Top - 4.65
Middle - 3.29
Bottom - 0.00

any thougts? I just knew my problem wasn't going to be that easy.

[PlainBill]

Re: Problem with Viewsonic VG920 lcd monitor

Plainbill-

Thankyou for that part number I found the reset controller. I do have another issue though. From the other posts



I did take off the reset controller to verify that this is the problem and guess what? It was, but I have another issue now. Although it did turn on and I saw the viewsonic screen. I shut it off using the button I put it back together (plastic housing ect) it now will not turn on, again. I have no green light no screen at all. So what do you think might have happened now? I went ahead and redid all of the trouble shooting suggestions you gave and everything was the basically the same

large cap was 160 (meaning the fuse OK also right?)

voltage from the power supply wires:

Black
0.00

Brown
4.47

Red
14.47

Orange
0.00

Yellow
4.95

Green
4.95

Blue
0.00

Purple
0.00

Voltage Regulator
Starting from the top voltage regulator :
Left - 3.29
Middle - 2.46
Right - 2.64

Top - 4.65
Middle - 3.29
Bottom - 0.00

any thougts? I just knew my problem wasn't going to be that easy.

Well, the power supply is working properly. The question (of course) is why isn't the monitor turning on again. And that comes back to the processor.

At this point I don't remember what we covered on this, but if you position the part so the two leads are at the bottom and the single lead is at the top,, the lower leftlead is pin 1, Gnd; the lower right lead is pin 2, Reset. Check the voltage from pin 1 to pin 2. It should be 0 volts. If you touch it with the meter probe and the monitor comes on, you've established that the reset controller is required.

Also, if you did anything more than turn it off with the power button, then try to turn it on again with the button, check what you did; in particular check the cable from the logic card to the buttons.

PlainBill

[mrpd]

Re: Problem with Viewsonic VG920 lcd monitor

Acouple of quick questions for you ...

if you position the part so the two leads are at the bottom and the single lead is at the top,, the lower leftlead is pin 1, Gnd; the lower right lead is pin 2, Reset. Check the voltage from pin 1 to pin 2. It should be 0 volts. If you touch it with the meter probe and the monitor comes on, you've established that the reset controller is required.

By this above do you mean the reset controller? If so I can't put it back on, it turns out my problem was that the controller was fried. When I removed it it fell apart so I don't have it anymore.

Also, if you did anything more than turn it off with the power button, then try to turn it on again with the button, check what you did; in particular check the cable from the logic card to the buttons.

I tried to duplicate exactly what I did and nothing comes on. All I did was remove the reset controller and then I tried the button. The green light came on and the LCD did to. I shut it off and tired it one more time and it came on again. I then put the lcd bck together (plastic housing ect..) and now it don't work. Go figure. I did looked at all the cables when I took it apart to redo the trouble shooting suggestions to make sure they are all connected but that doesn't look to be the issue. The only thing is that when I first tried the LCD it was opened up and the audio speaker connection (the speakers themselves) were unplug. I don't really think this would have anything to do with the LCD not turning on but thought I would atleast tell you.

[PlainBill]

Re: Problem with Viewsonic VG920 lcd monitor

Acouple of quick questions for you ...



By this above do you mean the reset controller? If so I can't put it back on, it turns out my problem was that the controller was fried. When I removed it it fell apart so I don't have it anymore.



I tried to duplicate exactly what I did and nothing comes on. All I did was remove the reset controller and then I tried the button. The green light came on and the LCD did to. I shut it off and tired it one more time and it came on again. I then put the lcd bck together (plastic housing ect..) and now it don't work. Go figure. I did looked at all the cables when I took it apart to redo the trouble shooting suggestions to make sure they are all connected but that doesn't look to be the issue. The only thing is that when I first tried the LCD it was opened up and the audio speaker connection (the speakers themselves) were unplug. I don't really think this would have anything to do with the LCD not turning on but thought I would atleast tell you.

Again, I wasn't clear. Ignore the fried reset controller. I'm interested in the voltages on the pads where it was soldered. With the monitor plugged in, what is the voltage across the two 'bottom' pins. If it reads 0 volts and the monitor will not come on, you have a problem, more testing lies ahead. If it is at 0 volts and now the monitor comes on, the input is floating and you need the reset controller. If it is at 2 volts or higher, try shorting the two pins together and see if then you can get the monitor to start by pressing the power button.

PlainBill

[mrpd]

Re: Problem with Viewsonic VG920 lcd monitor

PlainBill

holding the black probe on a screw and touching the solder pads the voltages are left - 0.00, right - 0.12 and the top - 4.95. I also did a reading across the two 'bottom' pins by touching the black probe on the left and the red on the right and it read 0.12. I tried shorting the two pins together but still nothing no green power light or the LCD turned on.

[PlainBill]

Re: Problem with Viewsonic VG920 lcd monitor

PlainBill

holding the black probe on a screw and touching the solder pads the voltages are left - 0.00, right - 0.12 and the top - 4.95. I also did a reading across the two 'bottom' pins by touching the black probe on the left and the red on the right and it read 0.12. I tried shorting the two pins together but still nothing no green power light or the LCD turned on.

.12 volts should be low enough. Now, this may seem to be a stupid question, but you DID hit the power button several times, didn't you?

PlainBill

[mrpd]

Re: Problem with Viewsonic VG920 lcd monitor

.12 volts should be low enough. Now, this may seem to be a stupid question, but you DID hit the power button several times, didn't you?

PlainBill

Yes sir I did but still nothing.

[PlainBill]

Re: Problem with Viewsonic VG920 lcd monitor

Yes sir I did but still nothing.

At this point I'm pretty much out of ideas other than installing a new reset controller. I don't have a great deal of confidence it that, however.

PlainBill

[mrpd]

Re: Problem with Viewsonic VG920 lcd monitor

PlainBill-

I hear you, I guess this is one LCD that just can't be fixed with a simple solution. It would probably take more money then it is worth and nowadays with LED monitors being so cheap you can buy a new one, rather then sink alot of money into fixing an older LCD. IMO though it was worth the time and effort to try. I really do appreciate all of your time and effort and putting up with a noob and walking me through the diagnostic process to try and trouble shoot and fix this LCD.

Thank You again,
PD

[12ax7a]

Re: Problem with Viewsonic VG920 lcd monitor

yes, i have qty 4 x acer 19" units in my lab all running with this mod. all good .. no problem.

4-16-11

[dtr20]

Re: Problem with Viewsonic VG920 lcd monitor

I realize this is an extremely old thread, but if you still haven't figured out the problem with the monitor, I would like to solve it for you. The problem isn't the power supply board, instead, its the audio/video board. I have fixed probably about 5 of these monitors (more to come) and its always the same problem. It looks like the monitor is not getting any power. Buy this circuit board
B-00006666. It will cost you $36 with normal shipping and it should fix the monitor. We have a bunch of these at my work and they keep dying. I take them home, replace the circuit board, and I have a working monitor.

[otoluk]

Re: Problem with Viewsonic VG920 lcd monitor

Which one is this? how does it look?

http://store.viewsonic.com/html/ibeC...=b&item=749640

[dtr20]

Re: Problem with Viewsonic VG920 lcd monitor

thats it, really easy fix