Proview LB 2006 W Monitor

[Joseph67]

Hi all,
My Proview LB2006W monitor went blank after a slight smell of smoke.
I found that on the logic board, transistor Q4 was burned out.
As it was an SMD, it was impossible to read anything on the burned body.
It is the second transistor to the right of connector JP2, the first being Q5 (t04 on it) than Q4 and after that TC4 a 10u/16v electrolytic capacitor.
Just above Q4, there is an empty space for an electrolytic capacitor TC6.
Is there anyone on the forum who knows what transistor the burned one can be replaced with?
The monitor has been waiting for this for about a year or so, but it would be nice to have it fixed as it is a wide screen monitor.
Thanks for any assistance with this.
Regards,
Joseph.

[alexanna]

Re: Proview LB 2006 W Monitor

There a lot of members that have power supply or even monitors sitting around, that I am sure would be willing to help you. A lot of manufactures of monitors will on occasion use the same power supply in a different make of monitor.
If you could supply a high resolution photo using the managed attachments feature it would be helpful.
The part number and revision of the power supply is also needed

[Joseph67]

Re: Proview LB 2006 W Monitor

Hi Alexanna,
Thanks for the quick response and the burned transistor is on the logic board and not on the power supply, but for the problem it is just the same.
I'll add a picture of the board and hope that the resolution is good enough.
I had to reduce it or the file would have been too big.
This is the area where the burned transistor used to sit.
Regards, Joseph.

[alexanna]

Re: Proview LB 2006 W Monitor

I just did a very quick search within Badcaps and Proview and viewsonic names came up as being similar design. Your quality of your photo was adequate but there I just not enough of it to make head or tails of the entire board.
Please post photos of all the boards so I can get a general idea what everything looks like.
I have a few Viewsonic monitors sitting around.

[mbates14]

Re: Proview LB 2006 W Monitor

That transistor is burned because the T-con failed on the panel.

you have no choice but to source a new panel. Sorry. I have been there a couple times with similar models. same transistor blown.

Turns out the t-con shorts out. If you can fix the t-con, you might be able to get something done.

But either of my cases, there was a dead hard short in the t-con somewhere and couldn't track it down. and since small panels, the T-con is integrated part of the panel and is NOT replaceable.

[Joseph67]

Re: Proview LB 2006 W Monitor

Hi all,
Thanks for the fast response.
About the panel being faulty...I was afraid of something like that as the connector is indeed the one to the panel.
Still, what is the T-con?... the panel controller board?
As for a picture of the entire board, please see below.
I had to reduce the size or it would have been too big.
Apart from this board, there is only the power supply and that seems to be fine.
I'm afraid that it might be the problem as "mbates14" mentions, but it would be still worth to try with a new transistor.
If it burns again we know that it is the panel controller and indeed in these small panels it is not a separate board as in the TV sets.
I'm in to try a transistor but...what type?
Any suggestion is welcome.
Thanks.
Cheers, Joseph.

[Scenic]

Re: Proview LB 2006 W Monitor

the t-con board is the one on the panel itself.
for "smaller" panels, it's usually at the top of the back of the panel. sometimes behind a metal shield.

on bigger panels (like 32+" LCD TV's), it's replaceable. on smaller ones (AFAIK up to 26") it's usually directly attached to the panel..

[Joseph67]

Re: Proview LB 2006 W Monitor

Hi Scenic,

Thanks for your reaction.
I left the faulty board at hand since I found the problem on it, but will have to dig around a bit for the rest of the bits of this monitor.
I'll get back on this if anything can be done or whatever the developments.
Herzlichen dank.
Cheers,
Joseph.

[momaka]

Re: Proview LB 2006 W Monitor

Joseph67, do you have a multimeter? If not, get one and also take some good, close-up pictures of the entire panel/t-con board.

As far as replacement transistors, I'm not quite sure what to advise you, but we can worry about that later after we get the panel/t-con board checked out. It is possible that there is a short on the panel board. No worries, though. Those panel/t-con boards are actually repairable. From what I've seen so far, it's always a shorted ceramic cap. The tricky part is finding it, but that's not as hard as you might think.

My Proview LB2006W monitor went blank after a slight smell of smoke.

Blank as in white(ish) screen or no power at all (as in no power button lights)?
White screen is typical of shorted panel board. Fairly easy to fix, though.

[Joseph67]

Re: Proview LB 2006 W Monitor

Hi Momaka,
Thanks you for your response and I guess you're tight.
First would indeed be to get the LCD's t-con board fixed and I think that following the connection from the burned transistor to surrounding components on the t-con might help a lot in localizing the shorted component.
Most components on these boards (in TV sets anyway) are SMD and indeed, they go shorted, but from my experience mainly in power supply's, but I will dig for the rest of the monitor and give it a go with the multimeter.
I'll get back on this once there us an update.
Cheers,
Joseph.

[momaka]

Re: Proview LB 2006 W Monitor

First would indeed be to get the LCD's t-con board fixed and I think that following the connection from the burned transistor to surrounding components on the t-con might help a lot in localizing the shorted component.

I think there's a slight confusion here...
That board with the burned transistor you uploaded pictures of is called the video/logic board. The panel/t-con board is the one that is attached to the LCD panel (hence why I call it just panel board) and is usually hidden under a metal cover, as Scenic pointed out. This is the board you need to check first. Once you find it, post some pictures of it, especially of the area around the inductor. Basically, that area is the power supply section of the panel board and is usually where you'll find the problem (if any). I can actually point you exactly to the components that need to be tested.

[Joseph67]

Re: Proview LB 2006 W Monitor

Hi Momaka,
I do realize that the board I posted the picture of is the video board, but as the burned transistor tracks lead to the connector that goes to the t-con board, it might help to follow this track to the connector and than on the t-con board from it's connector to the short on this LCD control board. As soon as I dig it out of the stack of stuff sitting under my work table, I'll make a picture of it and post it on the forum.
Thanks for all the help.
Cheers,
Joseph.

[Joseph67]

Re: Proview LB 2006 W Monitor

Hello again Momaka,
After all it was not that bad to find the bits from the monitor between the mess underneath my work table.
Following the track of the burned transistor it did lead me to the second last pin on the connector to on the t-con board( pin 31 and joined to pin 29).
This pin's track goes directly to a fuse F5.
Fuse 5 is OK and the components around this fuse don't show 'heat' effects and are not in short.
The pass true on the board is a test point on the back of the t-con board 5v1 so obviously in correct working conditions one should be able to measure 5v on this test point.
It looks as if the burned transistor was providing the +5V to the t-con board.
I have made about 15 pictures and discarded most of them as the flash would make the picture useless. The 2 that I made without the flash are the ones I'm attaching.
Perhaps I should apply +5V to the pin on the connector and see what happens or check what is getting hot if not smoking.
Still I'll wait for your opinion as you obviousle have more practice with these things.
Thanks and best regards,
Joseph

[momaka]

Re: Proview LB 2006 W Monitor

Excellent pics, exactly what I needed.

Perhaps I should apply +5V to the pin on the connector and see what happens or check what is getting hot if not smoking.

At this point, this is not such a good idea. The t-con board is very likely multi-layer, and if a trace in between the layers burns, you won't be able to fix it. Fuse (F5) also might blow. We may provide the monitor with external 5v later on, after we've verified that everything is in order on the t-con board.

Fuse 5 is OK

I'm assuming you tested the fuse for continuity with a multimeter, not just a visual inspection, correct?

It looks as if the burned transistor was providing the +5V to the t-con board.

Precisely. The t-con board uses the 5v rail to produce several different voltages - usually 3.3v via a linear regulator, as well as a main boosted voltage rail of around 12v. The 3.3v is used by the data/video processor. The 12v rails is used by the buffers and also to produce two more voltage rails - one negative around -5 to -15v, and another positive one around 15 to 28v. These two are used by the LCD panel.

In the case of your t-con board, there's two linear regulators - U1, a 3.3v reg. and U4, a 1.8v reg. These very rarely fail, so we'll leave them alone for now.

To get a good idea about the rest of the circuit, though (and to aid with the troubleshooting), I suggest you get the AAT1164C datasheet. This IC (U11 on your board) is responsible for the main boosted rail as well as the other two boosted rails derived from it. Page 2 and 14 of the datasheet show a typical circuit.

In your monitor, the main boosted rail starts from the cathode of diode D10 (the side marked with the white stripe). Based on what I've seen, many times one of those small multi-layer ceramic capacitors will fail and go shorted (or near shorted) in either the main boosted voltage rail or in the two secondary boosted rails.

So with that said, do the following measurements and post the results here:
1) check resistance between ground and either terminals of fuse F5
2) check resistance between ground and the cathode of D10
3) check resistance with (-) probe on cathode of D10 and (+) on fuse f5
4) check resistance with (+) probe on cathode of D10 and (-) on fuse f5

For items 1) and 2), put the (-) probe on ground.
For all 4 measurements above, use 2000 Ohm scale if your multimeter is manual ranging.

Item 1) is to see if the 5v input is shorted while item 2) checks whether the main boosted voltage rail is shorted. Items 3) and 4) check diode D10.

Alright, it's 3:30AM here so that's all for now . Hope I'm not giving you a headache with that stuff .

[Joseph67]

Re: Proview LB 2006 W Monitor

Hi Momaka,
Thanks for your time to help me with this, I do appreciate it a lot.
I've just downloaded the data sheet and printed it out.
As I am retired and the rest of the family is still busy with school and that sort of things, I am in charge of preparing lunch and the daily shopping so I can not just drop everything and get on with the monitor despite that I would like to.
(today is oven roasted chicken + fries).
This afternoon after lunch I will get on with it.
The fuse F5 is OK and tested with the multimeter yesterday.
I'll check all the points you indicated and give you the readings.
The multimeter I use is one of these digital ones but for a lot of measuring I often use one of the 'old' analogue AVO meters from just after WW2!
Especially for fault finding on circuits in my car and antique car radios, I prefer the AVO (less than 50K/V load).
Cheers, Joseph.

[Joseph67]

Re: Proview LB 2006 W Monitor

Hi again Momaka,

I have checked the items you mentioned and here are the results:

1) check resistance between ground and either terminals of fuse F5 : No resistance at 2K scale.
2) check resistance between ground and the cathode of D10 : 228ohm
3) check resistance with (-) probe on cathode of D10 and (+) on fuse f5: 1.863 Ohm on 2K scale.
4) check resistance with (+) probe on cathode of D10 and (-) on fuse f5: No resistance on 2K scale.
Over the diode itself I measure about 1.9K ohm and with probes inverted no reading at the 2Kscale.
From these measures it looks to me as if the diode is Ok.
The voltage rail from the diode's cathode with 228 ohms at 5V doesn't look too high either with 45.6 Ma I think, so.......?? why did the transistor on the video board burn out?
I've measured most of the C's in the surrounding of diode, U11 and fuse and so far no shorts.
I even checked with a magnifier if any component shows any signs of having been hot and the soldering been melted, but nothing of the kind.
Actually, this sort of exercise is precisely what I need and it will certainly not give me a headache, just the contrary.
I have always worked in electronics but the newest stuff is sometimes a bit too new for me and looks so fragile that getting your hands in it, often looks as if it will get more damaged.
It's like the t-con boards connections to the panel, they look to me as if they are glued to the panel but lucky enough flexible enough so one can turn over the panel.
Anyway, we still have the problem.
Do you have any more suggestions what to look for?
I hope I don't take too much of your spare time and look forward to your communication.
Best regards,
Joseph.

[momaka]

Re: Proview LB 2006 W Monitor

I have checked the items you mentioned and here are the results:

1) check resistance between ground and either terminals of fuse F5 : No resistance at 2K scale.
2) check resistance between ground and the cathode of D10 : 228ohm
3) check resistance with (-) probe on cathode of D10 and (+) on fuse f5: 1.863 Ohm on 2K scale.
4) check resistance with (+) probe on cathode of D10 and (-) on fuse f5: No resistance on 2K scale.
Over the diode itself I measure about 1.9K ohm and with probes inverted no reading at the 2Kscale.
From these measures it looks to me as if the diode is Ok.

Yes, it seems that D10 is indeed fine (I'm guessing that for item 3, you got 1.863 kOhms, not 1.863 Ohms, though).

The voltage rail from the diode's cathode with 228 ohms at 5V doesn't look too high either with 45.6 Ma I think, so.......??

Well, the cathode of D10 is the main boosted voltage rail, so once the monitor is running, that voltage rail is actually sitting somewhere between 10v and 15v, depending on how the circuit was designed. But that's all irrelevant. The point is that a resistance of 228 Ohms between ground and cathode of D10 shows that there are no shorted capacitors on that rail.

Do you have any more suggestions what to look for?

Yes.
The main boosted voltage rail (cathode of D10) is used to produce 2 (or perhaps more?) other voltage rails. The AAT1164 datasheet lists these as the Positive and Negative LDO drivers. You can see a circuit of those rails on page 20 in the datasheet.

These two voltage rails also have some ceramic caps on them as well as schottky rectifiers. Thus, this is what we need to check next.

So, fire up you multimeter again and measure resistance for the following items (using 2 kOhm setting again):
1) C21, C20, C50, C60
2) C61, C503?, C213, C504
3) D21, D20, D50, D60

The diodes I mentioned in 3) usually look like this internally:
https://www.badcaps.net/forum/attach...1&d=1294381123
(pins 1 and 3 may be switched, though)

---------

The multimeter I use is one of these digital ones but for a lot of measuring I often use one of the 'old' analogue AVO meters from just after WW2!

Wow, nice! They don't build them like that anymore, do they .
Puts my cheap 830D to shame for sure.

I hope I don't take too much of your spare time

Don't worry, I'm usually here every other day or so anyways. With that said, feel free to reply whenever is convenient for you.
School tries to keep me busy sometimes, but when I get fed up with homework and whatnot, I just come here .

[Joseph67]

Re: Proview LB 2006 W Monitor

Hi Momaka,
I've done all the homework you sent me and first I thought that we hit a faulty capacitor as C504 gave me a reading on both polarity's at just over 1Kohm.
So, I un-soldered this capacitor but unfortunately the reading on the pad's was the same and the capacitor on it's own was not shorted either, so I've placed it back where it came from.
Al these other componentsC21, C20, C502 (C50 has no component and is not in the same area), C60,C61, C503, C213, C504,D21, D20, D50, D60 and all the others in the area don't show any short circuit either.
The only other reading was on C30, in one direction I read 646 Ohms and in reverse 438 Ohms, but that it is probably the circuit and not the C.
I even went back to the video card and checked the capacitors on this 5V output as there are some of these ceramic SMD capacitors as well, but no luck either.
As I was checking with a wire counter as magnifier the text on the transistors of the video card, I found very small traces of solder between the pins of the connector to the panel between the 5V and the ground pin next to it, but is was such a small bit that I find it hard to believe thát could have been the reason of the burned Q4.
(Sorry for jumping to this but I just remembered this)
Googeling a bit I found the spec. sheet of the panel (AU Optronics) and I'll attach it for reference. It seems that this same panel is used in different brands of monitors, but than :"What's in a name"
There is still the question on what transistor to use for the burned one Q4) on the video card.
Q5, next to the burned one is marked as "t04" and there are 5 more of the same on the board one "A4t", 3# "A7W" and one really big-ish one Q2 "74A5Z" as it is using the board as a heat sink
Than by the size of the pad layout compared Q4 with Q5, it looks as if Q4 was slightly bigger than the others but smaller than Q2.
I just wonder if there are that many different SMD transistors anyway as there is hardly space on them to print a code number on them.
It is even worse with the ceramic capacitors as the only difference is their size with no text al all!
As you see, I'm jumping from one thing to the other as so far it looks as if most of the testing does not give errors as such.
Besides, I would expect that with fuse 5 between the 5V supply of the video card and the 5V rail of the t-con not blown it would be weird to have a full short, wouldn't you think?
Do we still have options?
I hope you can come up with some more things to check.
Best regards,
Joseph.

[momaka]

Re: Proview LB 2006 W Monitor

Al these other componentsC21, C20, C502 (C50 has no component and is not in the same area), C60,C61, C503, C213, C504,D21, D20, D50, D60 and all the others in the area don't show any short circuit either.

Well, those diodes rarely short out. However, the reason I suggested checking them is because they can be used to find bad ceramic caps, particularly because diodes should show a reading in one direction but not in the other (at least when checked with 2 kOhm setting). A bad ceramic capacitor will throw off these measurements and the diode will show a reading in both directions.
Keep in mind that ceramic capacitors don't necessarily have to be shorted to be bad. They could just be "partially shorted". I've had one that was showing ~33 ohms in both directions, in and out of circuit. I'd say anything under 100 Ohms (especially in the positive/negative LDO drivers section) should be considered as suspect. If you didn't get any readings like that, though, then the t-con board is likely fine.

This brings us back to the original question - why did Q4 on the video/logic board burn out? Unfortunately, I can't give you a definite answer on that. This is why I suggested checking the t-con board. However, it could be that Q4 just overheated. Or it could also be that Q4 had a defect from the factory and it took it some time to show up. Many of the ceramic capacitors seem to act that way - they work fine for a while, then they short out.

With that said, if everything checked out "okay" on the t-con board, the next step is to feed it 5v with an external power supply. More precisely, connect everything in the monitor the way it should be, and power it on, then feed 5v to the t-con board. I suggest you connect the external 5v PSU in series with your multimeter (and use it as an ammeter) to see how much current is going to the t-con board. I would guesstimate 0.8A to 1.2A is where it would be - this is based on the current I measured for a 19" SyncMaster. Note, however, that if the LCD monitor's power supply has any labels on it stating the maximum output current on the 5v rail, then the t-con board should not exceed that current.

Lastly, as you feed 5v to the t-con board, have your finger over the AAT1164 chip. If there's something wrong with the t-con board, that AAT1164 chip will get very hot in less than a second - so do beware and be ready to pull your hand if this happens. (This is how I found there was something wrong with the t-con board on one monitor before I knew how to check t-con boards.)
Also, regardless of what the external power supply is, make sure to connect its ground to the monitor's ground (i.e. anywhere on the chassis).

If the t-con board appears to work fine and nothing overheats, you should see the usual start-up image on the monitor, such as "No signal", "Proview", etc. If you don't, let me know.

Once we establish the t-con board is working, then we will worry about finding a replacement for Q4 on the video board.

----

Besides, I would expect that with fuse 5 between the 5V supply of the video card and the 5V rail of the t-con not blown it would be weird to have a full short, wouldn't you think?

No, not necessarily.
The voltage rails for the positive/negative LDO drivers are derived from the main boosted voltage rail. Thus, a short on any of those would not register as a short circuit on the main boosted voltage rail, much less the 5v rail.
The same monitor I mentioned above where I noticed the hot IC chip is the one that has a shorted LDO driver voltage rail. The fuse on it was not burned, but the monitor would not display any image.

I just wonder if there are that many different SMD transistors anyway as there is hardly space on them to print a code number on them.

There are quite a few of them actually. Those numbers are usually just reference numbers. You then use a SMD code book that ties up those reference numbers with the actual SMD component numbers.
Normally I use this:
http://www.marsport.org.uk/smd/mainframe.htm
Unfortunately, this was last update in 2006, so you may not see some components listed.

As for the SMD ceramic capacitors - I just replace them with ones of the same size (I know this is not the best way to go about that, but then again, what else can you do?) This method seems to work fine, though.

[Joseph67]

Re: Proview LB 2006 W Monitor

Hi Momaka,
Had to skip some days working on the monitor as my back complained about the workload, but it was actually a bad nights sleep, turning around and around that caused the old problem to become really bad, but after some days on painkillers and other chemicals from the doctors, I'm back to business.
Yesterday I repaired a Mercedes Benz outside temperature sensor that cost as a spare from Mercedes 64 Euro + vat(18%) and the only thing wrong in it is a 50 cent thermistorv (3k3 pearl NTC) so it was well spent time and I left an article about "how to" with pictures on our local Mercedes Benz forum.
On the monitor front I am still digging as the 5V external supply is trying to drink about 2.5A and the diode goes hot very fast (it's still OK) (U11 does not get warm!).
I removed C 12, C13, C15 and R16 and 520 as they are the ones that are directly connected to the cathode of D10 and gave me a reading of about 10ohms over each of these.
When unsoldering R 520, it jumped from my tweezers over my workspace and I spent about 1/2 our trying to find it but no luck.
As it is just a 0 ohms one, I can replace it from a scrap board with a lot of SMD components on it (a t-con board I saved from a broken Medion monitor screen).
It will be a bit of digging as after the resistors, the track seem lo lead to a second or what knows layer.
On one of the pic's of the t-con board you can just see the track from R16 to one of these through holes and the one from R520 is close to it.
Hope to get on with it tomorrow, but it begins to look as a not so easy one.
I will need to make a new tip for my soldering iron as these components are getting too small to remove (and place back) for a standard tip and I think I still have a piece of copper rod of the right size somewhere from when I made a tip for the bigger size SMD components some years ago.
They seem to shrink by the year and soon you can only solder them with hot air but for the hot air soldering machine I once bought in Japan, I don't have a nozzle for these type of components and first of all I will have to have a good think about of where I have stored it years ago after the last use.
Perhaps I could modify one of the smallest IC nozzles so it will only blow from 2 of the little pipes ...hmm, hmm.
I like to get this monitor back to work as it is a 9 :16, 20" model and would be great for watching movies & TV.
I'll come back on it as soon as I have some news.
Best regards,
Joseph.