Viewsonic VX910

[jetadm123]

Re: Viewsonic VX910

Quote from ajsemtb: I think someone said to change out the 2 ceramic capacitors... What are those and what do they look like? Also, what is the white "square" thingy on the top of the board that has a matching one on the other side?

If you're talking about the "square" units wrapped in yellow tape, those are the inverter transformers, which generate the high voltages required to light the backlights.

As for the two capacitors: I think what the person is talking about are the brown (or dark orange) caps directly below each inverter transformer. From memory, I think they are polypropolene caps stamped "154" and rated at 250volts. These caps have a tendency to fail and might be the cause of your problem.

[retiredcaps]

Re: Viewsonic VX910

I didn't replace the really big one or the tiny one right next to the big one. I replaced the tiny transitors on the bottom. There is a difference now, as the screen at least flickers ever 2 seconds when the light blinks now. That is new. I hear a clicking each time it tris to turn on though.

When I installed the transitors, I tested them compared to the pair that I think work, and they gave me the same readings. Well, after my test, I think they shorted again, because for voltage they were at .270 and now they are .023. So that sucks.

The little cap is sometimes called a startup/run cap. It is usually in the 1uF/2uF 50V range or something like 22uF/50V. That cap doesn't have to bloat to be bad.

The clicking sound maybe the SMPS trying to startup. The little cap helps the SMPS startup.

Which leads to ... replace the little cap. That may solve the problem?

If the transistors are shorted again, resolder all the transformer pins (the 2 yellow things marked with T). Remove the old solder and resolder with fresh solder.

edit: Here is PlainBill talking about the startup cap ...

https://www.badcaps.net/forum/showpo...97&postcount=2

[ajsemtb]

Re: Viewsonic VX910

Update, it didn't work... I recapped the 4 "main" ones, the 470uFs and the 330uFs. I didn't replace the really big one or the tiny one right next to the big one. I replaced the tiny transitors on the bottom. There is a difference now, as the screen at least flickers ever 2 seconds when the light blinks now. That is new. I hear a clicking each time it tris to turn on though. I heard it before also, when the ps was on my bench I plugged it in and heard a clicking as it cycled through.

When I installed the transitors, I tested them compared to the pair that I think work, and they gave me the same readings. Well, after my test, I think they shorted again, because for voltage they were at .270 and now they are .023. So that sucks. Luckily I bought 4 to do all of them, but Im pretty sure its just the one side thats fried. SO, that being said, besides replacing the only 2 caps I didn't change yet, what else could I test? what would be clicking?

Also, after my bench test, the really big Cap is holding voltage. 12v and with my DMM on it it slowly goes down. Its been almost 10 minutes and I'm at 7v and counting... Any thoughts?

I think someone said to change out the 2 ceramic capacitors... What are those and what do they look like? Also, what is the white "square" thingy on the top of the board that has a matching one on the other side?

Thanks again for all your help. I'm not giving up yet...

[ajsemtb]

Re: Viewsonic VX910

Ok, well I ordered new caps (all except the very big one...probably come back to bite me but...) new transistors that flush mount the bottom, and a couple diodes that were mentioned that go out. All in all $12 including shipping. I ordered panasonic mainly FM but the little one was an FC. I'll update and let you all know how the repair goes.

[retiredcaps]

Re: Viewsonic VX910

Ok, well I'm sorry again, but I didn't remove it from the circuit... I thought I could test these still installed to the board. :/ SO, this all being said, which caps do I need to buy, and when I type in the search engine at the digikey or mouser or whatever the other one was, there are 600 options that all say the same thing for different prices. What specifically should I buy for caps and the tiny transistors on the bottom of the board? What has been used in this installation before and has worked? The parts range from .29 to 2.89 which is a heck of a swing, and I would like to do this repair for less than buying a new power supply board.

You can test transistors in circuit, but sometimes depending on how they are laid out, the results may not be 100% accurate so you need to remove them and test them out of circuit.

You need to make a list of the uF V, height and diameter of each capacitor and then follow PlainBill's instructions at

https://www.badcaps.net/forum/showpo...33&postcount=2

There is no "standard" list because each board can be a different revision and have different cap values (hence the request for pictures). Panasonic FM or FC caps are good low ESR choices.

My board "looks like" someone else may be a false sense of security. It is always better to make sure by reading the values of the caps on your own board.

Once you compile a list, some members here can verify.

[Krankshaft]

Re: Viewsonic VX910

Xicon? Are they blue or light blue by any chance? If so, perhaps someone has recapped it indeed (with the wrong type of caps, that is). If I'm not mistaken, Radio Shack sells those Xicon caps - and they are definitely not suitable for monitor repair.

Not only are they not suitable for monitor repair Xicon's light blue GP caps are 85C rated. Only their radioactive green GP caps are 105C rated and even those aren't suitable since they're GP.

Definitely a Radioshack special you've got there.

When measuring the transistors be sure to use the diode check function on the meter and not the resistance function. You're testing for voltage drop not resistance.

[ajsemtb]

Re: Viewsonic VX910

Ok, well I'm sorry again, but I didn't remove it from the circuit... I thought I could test these still installed to the board. :/ SO, this all being said, which caps do I need to buy, and when I type in the search engine at the digikey or mouser or whatever the other one was, there are 600 options that all say the same thing for different prices. What specifically should I buy for caps and the tiny transistors on the bottom of the board? What has been used in this installation before and has worked? The parts range from .29 to 2.89 which is a heck of a swing, and I would like to do this repair for less than buying a new power supply board.

Regarding the transistors mounted to the heat sinks, I'll remove them tomorrow and retest and post results.

Thanks again for all your help, I'm learning a lot as we go along.

Also, I have an Insignia 32 lcd model# NS-32LCD that has died. It too has a common problem with caps going bad on the power supply board, and again, mine aren't bulged. Which doesn't mean they aren't bad, but I honestly care more about getting my tv working again than this monitor at this exact moment only because I have 2 22" monitors another 19" and my laptop monitor making up my array, this particular monitor just went out, and I replaced it. BUT my TV not working sucks way more... LOL I have searched these threads, but don't see the Insignia come up, but I'm too new to start a new thread, and I don't want to hijack this thread, so I'm trying to use my experience from fixing the monitor before I tackle my TV.

[RJARRRPCGP]

Re: Viewsonic VX910

I like the soldering videos by Curious Inventer on youtube.com.

+1

I finally didn't feel like I had to guess!

[retiredcaps]

Re: Viewsonic VX910

1-2 the number starts at 1k and starts climbing, and doesn't stop
1-3 .1ohms
2-3 is 4.7m and counting down...

Also, I found the fuse, it was heatshrinked in black but I'm getting a reading of .2 to .1 ohms on it as well.

If pin1-3 on the transistor reads 0.1 ohms when it is out of circuit, it is definitely shorted (bad).

The fuse is okay at 0.1 or 0.2 ohms. Some multimeters have a lower resistance for their probes.

[ajsemtb]

Re: Viewsonic VX910

Xicon? Are they blue or light blue by any chance? If so, perhaps someone has recapped it indeed (with the wrong type of caps, that is). If I'm not mistaken, Radio Shack sells those Xicon caps - and they are definitely not suitable for monitor repair.

Yes they are blue and the 35v ones instead of the 25v ones I've been reading about.

And RetiredCaps, I don't have access to a camera right now, however, in the 5th posting of this thread are pics from PlainBill with the transistors boxed in Red. Those are the ones to which I'm referring. Also, I did a test on the transitors that are attached directly to the heat sink, and I'm not sure which leg is actually which, but number 1-2-3 from right to left when upside down I'm getting these ohm readings:

1-2 the number starts at 1k and starts climbing, and doesn't stop
1-3 .1ohms
2-3 is 4.7m and counting down...

Honestly, I have no idea what his means.. LOL

1-2 15.71m and counting down
1-3 9.05k
2-3 14.94k and counting down

Also, I found the fuse, it was heatshrinked in black but I'm getting a reading of .2 to .1 ohms on it as well.

https://www.badcaps.net/forum/attach...1&d=1280705628

https://www.badcaps.net/forum/attach...1&d=1280705635

[momaka]

Re: Viewsonic VX910

Also, looking at this board a little closer, I'm thinking these caps have already been replaced once. Well, the Xicon ones anyway.

Xicon? Are they blue or light blue by any chance? If so, perhaps someone has recapped it indeed (with the wrong type of caps, that is). If I'm not mistaken, Radio Shack sells those Xicon caps - and they are definitely not suitable for monitor repair.

[retiredcaps]

Re: Viewsonic VX910

Simple question, 120@500mV,2A gain or 82@500mV,2A gain?

Post a pic of the part that you are trying to replace. Posting pic guideline is at

https://www.badcaps.net/forum/showthread.php?t=1868

[ajsemtb]

Re: Viewsonic VX910

I'm went and looked at digikey for the transistors, and theres 6 different ones in the listings... Simple question, 120@500mV,2A gain or 82@500mV,2A gain?

http://search.digikey.com/scripts/Dk...672+&x=20&y=13

[retiredcaps]

Re: Viewsonic VX910

What are the fuses on this board? And to clarify, the transistors are are mounted to the heat sink?

Fuses are marked with the letter F. Some picofuses are PF. For example, F100 or PF701.

Transistors are marked with the letter Q. Transistors may be mounted to a heat sink.

Do caps get hot?

Caps can get hot. If they sit next to transistors and the heat flow is directed towards the caps, they will get hot and eventually die from heat and drying out.

[ajsemtb]

Re: Viewsonic VX910

Ok, now you can officially laugh at me... What are the fuses on this board? If they don't plug in somewhere, I wouldn't know they were fuses! LOL And to clarify, the transistors are are mounted to the heat sink? (other than the tiny ones on the bottom?)

Also, looking at this board a little closer, I'm thinking these caps have already been replaced once. Well, the Xicon ones anyway. The reason why, is a couple aren't sitting flush and the solder jobs on the back are good, but not great, and appear to have some heat coloring around the points that are similar to not careful soldering, but I suppose could be from the Caps... Do caps get hot? ANywho, I've seen on these posts where to buy these parts, so I will order the tiny little transistors, and the caps and hopefully have a working lcd again.

[retiredcaps]

Re: Viewsonic VX910

Also, that's probably why my tips die so quickly, I don't tin them after I'm done, just clean them and boy do they get corroded!

Yes, tin them after you are done. Tips are not cheap on quality irons.

1-2 9.8
1-3 9.4
2-3 .6 ohms

SO, I would say those ones are definitely fried...

That is definitely shorted.

Also, my caps are XICON. Haven't seen that name yet in these threads. Both those are CapXon.

Are there any other components I should/can check that regularly fail with these power supplies? What's the final recommendation for chip repair? Thanks in advance for your help. If the monitor works again, great! If not, that sucks, but oh well. Already bought a replacement, but I don't throw anything away that I "might" be able to fix.

I think any 19 inch LCD monitor is worth saving.

Members here hate Capxon and recommend replacing all the Capxon.

Caps do NOT have to bulge in order to be bad. They can out of uF tolerance and have ESR.

You can also test our transistors and voltage regulators for shorts (with power OFF and monitor unplugged). Test to ensure all fuses are good. They should measure 0.3 ohms.

I had zero soldering skills when I started, but I managed to install new transistors. The key to removing the old ones is to ADD a bit of fresh 60/40 solder. Then I use a solder sucker to remove all the solder. This is usually good enough so I can remove the old transistor.

[ajsemtb]

Re: Viewsonic VX910

WOw, those vids were great! Thank you for that. I got a lot of tips from those. Also, that's probably why my tips die so quickly, I don't tin them after I'm done, just clean them and boy do they get corroded!

Back to my chip: OK well, I'm not going to add pics, because it looks exactly like the chip above in this thread, however, I did my own test for the transistors and heres what I got, again top to bottom 3-2-1.

both on the right side were (closely enough to each other)
1-2 745 ohms
1-3 5.37k
2-3 4.51k

and the chips on the left

1-2 9.8
1-3 9.4
2-3 .6 ohms

SO, I would say those ones are definitely fried...

Also, my caps are XICON. Haven't seen that name yet in these threads. Anyone? They do not seem to be bulged at all. :/ there are 2 470uf 35v and 2 330uf 35v. Oh, and a big one 1000uf 400v and a little one 10uf50v. Both those are CapXon.

Are there any other components I should/can check that regularly fail with these power supplies? What's the final recommendation for chip repair? Thanks in advance for your help. If the monitor works again, great! If not, that sucks, but oh well. Already bought a replacement, but I don't throw anything away that I "might" be able to fix.

[retiredcaps]

Re: Viewsonic VX910

As for my experience, I'm a tinkerer, I have moderate soldering skills, but I am concerned about soldering those tiny little transisters... Any tips on soldering points that small? I have a 30 watt soldering iron and a 45 watt de-soldering iron, that I usually use to solder points on boards, because it makes pretty little points.. LOL and I can "cup" the molten solder in the nose instead of trying to feed wire solder into my iron tip.

I like the soldering videos by Curious Inventer on youtube.com. These are the 2 I suggest a lot to people, but he has much more on his channel.

http://www.youtube.com/watch?v=3NN7UGWYmBY

http://www.youtube.com/watch?v=I_NU2ruzyc4

[ajsemtb]

Re: Viewsonic VX910

Also check die Schottky Diode near those 2SC4672: D9 and D10

At a german board a guy with same problem wrote:
You can check both Inverters by R18,R22 and R20,23: if ok everyone should have 750 Ohm. If one Inverter is broken, the resistance should be lower

Technically, I wasn't doing a diode test. I was following this test that was on another thread in this forum. The thread was simply Viewsonic VX910 that was also discussing this problem. I haven't done the test on the transistors that was mentioned in this thread yet, as I went through a major cleaning upheaval in my office/shop/studio and my project was halfway reassembled to keep it together. I will hopefully get it back out this evening and test the points on the transistors and post the readings as well as pics later.

As for my experience, I'm a tinkerer, I have moderate soldering skills, but I am concerned about soldering those tiny little transisters... Any tips on soldering points that small? I have a 30 watt soldering iron and a 45 watt de-soldering iron, that I usually use to solder points on boards, because it makes pretty little points.. LOL and I can "cup" the molten solder in the nose instead of trying to feed wire solder into my iron tip.

[retiredcaps]

Re: Viewsonic VX910

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.

For a diode test, turn your multimeter to the diode setting.

Put black probe on side and red on the other. Record the measurement. Then reverse the probes and record the measurement.

One should read around 0.5 to 0.7 and the other should be 0L.