Dell S2309Wb monitor - Page 1
Forum section: electronics / repair

author: WaveyDipole
author_rank: Frequent Contributor
timestamp: March 04, 2018, 06:57:00 pm
content: I would like to ask for a bit of help with this monitor (Dell S2309Wb) which failed suddenly a few days ago. It is reasonably modern, manufactured 2009. The failure is manifest by the fact that the monitor switches on, shows the manufacturer logo and then the OS desktop display very briefly - for about 2 seconds - and then switches off.I have very little experience with LCD monitor repair and when I have looked at one or two in the past the trouble usually related to electrolytic capacitors which were failing due to age. Therefore this is the first thing I checked. All of them - checked out of circuit - seemed to have a very low ESR, well within the expected range.I am not sure whether to do a blanket replacement of caps or where else to look next? Blanket replacement of caps has not always resolved the problem. I appreciate that the system is comprised of the SMPSU, fluorescent tube drivers and logic board. Since an image is displayed, if only briefly, this tends to suggest that the logic board and inputs are OK. Since it does power up, this also suggests that the SMPSU is OK. So are we looking some sort of tube or inverter/driver failure that is triggering a protecton circuit that is, in turn, causing the SMPSU to shut down? I would point out that when it does light up for that couple of seconds, the display does seem evenly illuminated. I would therefore imagine that all illumination tubes are indeed working.I think I need a little help with the diagnostic process when dealing with LCD monitors and any comments on how to proceed next would be appreciated. BTW, I haven't found a circuit diagram yet.

author: Bratster
author_rank: Frequent Contributor
timestamp: March 04, 2018, 07:37:57 pm
content: When you say switches off,Do you mean it switches completely off no power indicator?Or does it go into standby?Or does the screen just go black?I just want to make sure I'm understanding you correctly.Sent from my Nexus 6 using Tapatalk

author: WaveyDipole
author_rank: Frequent Contributor
timestamp: March 04, 2018, 08:52:05 pm
content: Sorry I should have been more accurate with my description. I just fired it up again to test. The power light stays on and white so it is not going into standby. It would have changed to red for standby. The display just blanks. It does not appear to be caused by the OS as both Windows and Linux work fine on another monitor.

author: Bratster
author_rank: Frequent Contributor
timestamp: March 04, 2018, 08:59:26 pm
content: If you shine a bright light at the screen from different angles, and look at it from different angles, can you still see the desktop background sort of?It sounds like maybe the backlight driver is failing.If you can still sort of see your desktop background while shining a light on it, that is most likely the case.Sent from my Nexus 6 using Tapatalk

author: WaveyDipole
author_rank: Frequent Contributor
timestamp: March 04, 2018, 10:02:40 pm
content: It took me a while to get the angle just right, but yes, when the light goes off, the image is still there and only disappears when I power off the monitor. So you seem to be correct - the problem is with the backlight. There is only one 'main' PCB that integrates the SMPSU and the backlight driver circuitry. On the LHS where the backlight connectors are located, the PCB has two large IC-like packages. Each of these is wired to a pair of backlight conectors, so I guess each drives a pair of lights, there being two pairs in total. I tried disconnecting each light in turn, but this made no difference. I also disconnected each complete pair in turn with no difference either.

author: Armadillo
author_rank: Super Contributor
timestamp: March 04, 2018, 10:16:26 pm
content: Download the service manual from the web.From your description, you have checked all the electrolytics capacitors, so you have successfully opened up the monitor.Lay LCD face down, put insulation sheet onto panel and lay boards onto it. The objective is you are going to turn on the power so that you can test the components on the board. Inject in a VGA/HDMI signal and turn on the monitor as you normally would.Use the back of your finger to feel which IC is hotter. But I suspect and suggest followings; [Don't touch onto LIVE parts]!Use a can of freeze spray, momentarily spray onto the LDOs - U701 then U702 then switcher IC901, one at a time to identify the problem heating up IC [backlight LEDs will be lighted up].If you found the fault, you should know what to do.Alternatively, if you don't have a can of freeze spray, try putting a piece of heat sink onto the IC one at a time to see if it prolong the ON time. But I prefer the freeze spray.I don't write so much, but you should get the idea.Whether you use a isolation transformer or not depends on your skill and comfort level.

author: Shock
author_rank: Super Contributor
timestamp: March 05, 2018, 12:02:27 am
content: Quote from: Armadillo on March 04, 2018, 10:16:26 pmBacklight LEDs?Do you want to tell WaveyDipole and us why you think those components are a problem when it's the CCFL backlights (or circuit) not working?

author: WaveyDipole
author_rank: Frequent Contributor
timestamp: March 05, 2018, 04:48:55 pm
content: I assumed the monitor uses CCFL lighting due to its thickness, but perhaps it is just as well to be sure. I found a user manual, but the type of lighting does not seem to be stated there, which in itself suggests it is not LED. I found a service manual for the S2309Wc but not the S2309Wb and this seems to confirm that it is indeed using CCFL, but from the below I have reason to believe that there has been considerable revision between the 'b' and the 'c' version, as the board layouts do not match what I have. It would seem unlikely that the lighting technology will have changed from LED back to CCFL though.I did identify the on/off signal from the logic board to the main board, and can confirm that this goes high when the On switch is pressed, and it stays high. I am also seeing the DIM line (labelled BRT_AD on the circuit board) go high with two alternating going low square pulses, one long, on short, at regular intervals. They come on at power on for several seconds, stop for a couple of seconds, then resume again continuously.Page 57 has a diagram to follow in the event that there is no back light, but here it gets confusing. I checked the power at R802 - it was almost exactly 5.00v. The diagram states that it should be 13v. After the resistor and at the chip pin it is almost exactly 3.33v. IC801 pin 13 is also supposed to be 13v. I get 0v. So I looked back at the circuit. R802 should be between the power rail and Q801, not at IC801. Pin 12 of Q801 is VCC, but on this board it leads back to a capacitor. I decided to follow the circuit back from the On/Off signal pin. Instead of passing via a 10k resistor to Q801, which turns on Q802, which in turn supplies power to the IC turning it on, the line leads to a 4.7k resistor which then goes directly to pin 10 of IC801. So it seems the layout is different and perhaps a different IC part has been used in this version. Perhaps this explains why Q801 and Q802 cannot be found. So clearly the board layout did not match the circuit diagram. Evidently I need a circuit for the 'b' version, but so far, I have not found it.While I was at it, I did check the temperature of various semiconductors - including IC801 - with a temperature probe. Nothing seems to be running more than a degree or two above the ambient room temperature, except perhaps regulators, which run a little, but not much hotter than this.Since the 'On' signal seems to be present and the 4.7k resistor is OK, this would seem to point to IC801 as the source of the problem, although I firt need to figure out whether there is actually a 13v line on this board, because I am not seeing 13v anywhere. There should be 13v on one of the pins of the connector that runs between the two boards. I only see 5v and 3.3v lines and again, the pins are not in the order that they are shown in the service manual.

author: wraper
author_rank: Unknown
timestamp: March 05, 2018, 04:58:05 pm
content: CCFL inverter goes into protection. There are basically 3 most common things that could fail:1. Electrolytic capacitor failure in PSU secondary side / inverter power.2. CCFL transformer secondary winding failure.3. CCFL lamp failure.Of course there could be other issues in CCFL inverter but they are relatively rare compared to those 3.

author: wraper
author_rank: Unknown
timestamp: March 05, 2018, 05:16:11 pm
content: Quote from: Armadillo on March 04, 2018, 10:16:26 pmThis monitor has CCFL backlight.QuoteDunno about which model you are thinking about, but with 2 seconds before going into protection it's unlikely that overheat protection is kicking in. Also if overheat is so fast, no heatsink would help.

author: Armadillo
author_rank: Super Contributor
timestamp: March 05, 2018, 07:03:26 pm
content: Quote from: wraper on March 05, 2018, 04:58:05 pmYou should read before making the comment. He said the capacitors tested OK.Quote from: wraper on March 05, 2018, 04:58:05 pmTransformer winding failure has immediate effect. Either shorted or no output. What failure are you talking about?Quote from: wraper on March 05, 2018, 04:58:05 pmLamp failure has immediate effect. Either its flickering or not lighted at all. So what failure you are talking about that will light up for 2 secs?Quote from: wraper on March 05, 2018, 04:58:05 pmToo generalized, its not going to help but I agree there could be other issues.

author: wraper
author_rank: Unknown
timestamp: March 05, 2018, 07:35:25 pm
content: Quote from: Armadillo on March 05, 2018, 07:03:26 pmI only wrote about failures which usually result in such symptoms.QuoteYeah, and there is always only one transformer and one CCFL. Monitor lights up with one lamp and goes into protection after a short moment. Not to say CCFL sometimes is not completely dead yet but bad enough to cause protection kicking in.

author: Armadillo
author_rank: Super Contributor
timestamp: March 05, 2018, 08:05:25 pm
content: Quote from: wraper on March 05, 2018, 07:35:25 pmOP had did some troubleshooting and written his findings, let's hear some practical comments from those other than wayward comments, yeah!.

author: wraper
author_rank: Unknown
timestamp: March 05, 2018, 08:25:07 pm
content: Quote from: WaveyDipole on March 04, 2018, 10:02:40 pmI guess you mean transformers. Pretty large for being IC. Secondary windings should measure around 1k and be the same for both transformers.

author: AKM
author_rank: Contributor
timestamp: March 05, 2018, 08:33:08 pm
content: That capacitor on the secondary side next to the big main filter capacitor doesn't look happy to me. It could be that the capacitors are bad, and that the voltage ripple causes the protection to kick in.

author: WaveyDipole
author_rank: Frequent Contributor
timestamp: March 05, 2018, 09:08:05 pm
content: Quote from: wraper on March 05, 2018, 08:25:07 pmI have seen substrate devices even bigger than that in older equipment, but yes, that is my mistake due to lack of familiarity. I realised that when I had a close look at the circuit diagram earlier. Even though it does not match my board, from the general topology it does make sense that these are the output transformers.BTW, except for some very minor component differences, the board in the picture is practically identical to mine.It seemed to me that the next step would be to identify that IC801 and get a datasheet for it. It sits on the underside in between the two transformers. Looking through two magnifying glasses and casting light at different angles, I eventually managed to get 3 lines of numbers of that IC, namely, OZ9938GN, 84C03.2N, 08395. The first one of these identified it as a "LCDM Inverter Controller" and returned a datasheet. The pinout of this IC seems correct in comparison to my findings in that the On/Off signal goes to the ENA(ble?) pin 10. The operating voltage is 4.5 - 5.5v which is consistent with a 5v line, hence a VCC of 13v would make no sense here.I now have a couple of questions:Firstly, the DIM signal according to the datasheet can be analog or PWM. I would fully expect it to be digital rather than analog, but the signal I was seeing did not look like a PWM signal. It could possibly be a logic "1" as the line was high for most part, but it did still have some repetitive negative going square blips. Since the datasheet says "Positive dimming polarity" does this mean that dimming is "on" when the line is high? Or does it mean that a positive going (i.e. 0-5v) PWM signal is required to control dimming?Secondly, according to the datasheet this chip has open-lamp protection and over-voltage protection. How do I test for an open-lamp condition?The IC itself seems to be easy to obtain and quite cheap, so if I do not find any other problems I might perhaps order a couple.Quote from: AKM on March 05, 2018, 08:33:08 pmWell spotted, but that is not my board. Wrapper posted a photo for comparison I think. That capacitor on my board looks perfectly clean. Your point about capacitors is, of course, perfectly valid. Here are a couple of photos of my board:

author: wraper
author_rank: Unknown
timestamp: March 05, 2018, 09:36:29 pm
content: PCB around top transformer looks like it was overheating.

author: WaveyDipole
author_rank: Frequent Contributor
timestamp: March 05, 2018, 10:03:04 pm
content: Quote from: wraper on March 05, 2018, 09:36:29 pmAn interesting observation although I fear that the picture is a bit deceptive. It does look as there are brown blotches around that TX in the picture and there are a few blobs of residue around various components on the board, particularly across the top third and the underside. These blobs look dark if the light catches them at the wrong angle. Its this same residue that made it difficult to read the numbers on the IC. Still, it is difficult to tell and you may have been referring to something else? I did measure the temperature of both of these with the thermocouple earlier and with the CCFLs connected and neither seemed to be running particularly hot at the time, but I will not discount the possibility that you might be correct.

author: wraper
author_rank: Unknown
timestamp: March 05, 2018, 10:24:41 pm
content: Quote from: WaveyDipole on March 05, 2018, 10:03:04 pmWhy would they get hot when inverter is shut down after a couple of seconds? Did you measure secondary windings as I suggested? PCB is darker not only where flux residues are present and also on the bottom side as well.

author: WaveyDipole
author_rank: Frequent Contributor
timestamp: March 05, 2018, 10:56:52 pm
content: Quote from: wraper on March 05, 2018, 10:24:41 pmFair point and I had been looking into the pinout of those transformers so as do the measurements you suggested. There is a variance between the two transformers.Bottom transformer:Pri: 0.36ohmSec(top): 1.103kSec(bot): 1.101kTop (suspect) transformer:Pri: 0.30ohmSec(top): 1.707kSec(bot): 1.105kOn the first transformer the readings for the two secondaries are pretty close. On the suspect transformer the bottom secondary is also consistent with other transformer. However top coil is at variance and reading a much higher resistance. Is that sufficiently off balance to cause a problem? Is this likely to be the result of a failing CCFL tube stressing the TX? I see there are a few of these 4004 type transformers on eBay and am wondering whether to replace, but if this has been caused by the CCFL tube, my concern is that the replacement will fail in a similar fashion.

author: wraper
author_rank: Unknown
timestamp: March 05, 2018, 11:47:58 pm
content: Quote from: WaveyDipole on March 05, 2018, 10:56:52 pmThat transformer is dead, unlikely to be caused by CCFL as for that there is protection. You could also check 4 high voltage capacitors connected to secondary of the transformer, just in case.

author: fable
author_rank: Regular Contributor
timestamp: March 06, 2018, 12:05:25 am
content: Definitely dead transformer. Resistance difference on secondary windings must not be greater than 30ohm.

author: Shock
author_rank: Super Contributor
timestamp: March 06, 2018, 12:41:13 am
content: Just confirming you had the tubes disconnected for the measurement didn't you?

author: WaveyDipole
author_rank: Frequent Contributor
timestamp: March 06, 2018, 11:09:49 am
content: Well that would confirms the transformer is faulty then and is causing protection to kick in. I will order one of those I saw on eBay. The cheapest was only 3GBP. Is the letter after the first four digits significant? For example, on this board I have 4004R....., but the one I found was 4004L.....Thanks for everyone's comments which have helped me get this far.Quote from: Shock on March 06, 2018, 12:41:13 amYes I did. Board removed from chassis.Quote from: wraper on March 05, 2018, 11:47:58 pmHad a look at those. No cracking or any physical damage that I can see and measurements are consistent across both sets. I measured about 1.8Mohm across one pair and nothing across the other. Same for both pairs.

author: WaveyDipole
author_rank: Frequent Contributor
timestamp: March 06, 2018, 05:55:18 pm
content: In my previous post I asked whether the letter 'R' after the 4004 is significant. After a little more research today I have answered my own question and apparently it is. I also realised that when I measured the primaries yesterday, their resistance value would have been affected by the lead resistance as well as possibly contact resistance, so i measured them again, this time using the REL function of the DMM to deduct the lead resistance. Both measured at 0.15ohm. Since there are two coils in parrallel, this means that each primary is 0.3ohm, and as already measured, the secondaries are at 1.1k. The question now is where to find such a part?I did come across this site:http://www.lcdparts.net/Transformer3D.aspxUnfortunately nothing listed with the right spec.I can keep an eye on eBay in case anything pops up with the right code (4004R) but in the meantime, does anyone know of any other sources?

author: wraper
author_rank: Unknown
timestamp: March 06, 2018, 07:10:28 pm
content: With a bit of hacking you could use SMT variant of this transformer (4004Y) or TMS92515CT.QuoteThe only place I've seen it for sale is some Ukrainian websitehttp://lcdlamp.com.ua/1j-26064-001-tip-1/. BTW you may have more success if search it as 1J.26064.001

author: wraper
author_rank: Unknown
timestamp: March 06, 2018, 07:40:56 pm
content: You could also use 1J.26061.021 without any modification.

author: WaveyDipole
author_rank: Frequent Contributor
timestamp: March 07, 2018, 09:40:56 am
content: Thank you for these suggestions. I have attempted to order from the Ukranian site but the ordering process requires the purchaser to submit an order form which I have done. I am now waiting for them to get back to me.I did initially search on '1J.26064.001' but go no results until I changed the search engine! Searching eBay is proving tricky as well. Searching on the full 1j.xxx part numbers I just get motorbike parts! Maybe the system is getting confused by the dots? So I just tried 'inverter transformer 1J' and I found a used 1J.26061.021 from the Russian Federation which I now have on my watch list. The Ukranian company states they will get back to me within one day so I will wait and see what happens. Plan B is to order the used part from Russia.

author: wraper
author_rank: Unknown
timestamp: March 07, 2018, 09:51:26 am
content: Quote from: WaveyDipole on March 07, 2018, 09:40:56 amIt finds 1J.26061.021 with dots just fine.

author: WaveyDipole
author_rank: Frequent Contributor
timestamp: March 07, 2018, 10:12:08 am
content: Interesting that yours finds it an mine does not. I have attached a photo of what I got! I tried it in quote marks as well.

author: wraper
author_rank: Unknown
timestamp: March 07, 2018, 10:30:30 am
content: Quote from: WaveyDipole on March 07, 2018, 10:12:08 amYou need to search on ebay.com

author: WaveyDipole
author_rank: Frequent Contributor
timestamp: March 07, 2018, 10:49:02 am
content: Yes, just had a chat with eBay and discovered that. Since I'm in the UK I had been logged in and looking at the .co.uk site. Apparently it is something to do with seller preferences regarding which countries they want visibility. This is curious since they specify postage to the Uk... Anyway sorted for now and today's lesson is look on BOTH sites!

author: wraper
author_rank: Unknown
timestamp: March 07, 2018, 11:08:22 am
content: Quote from: WaveyDipole on March 07, 2018, 10:49:02 amYou need to pay additional fee for being listed on regional sites.

author: WaveyDipole
author_rank: Frequent Contributor
timestamp: March 21, 2018, 03:36:29 pm
content: I received the 1J.26061.021 I ordered from Russia today, but it seems these are not quite the same. The primaries measure about 0.35ohm each which seems close enough, but the secondaries measure 981 and 984 ohms respectively, which is some 120 ohms less than the good coil on the faulty one I have. I also notice that only 4 out of the 6 sections of the secondary are wound. Is it still safe to try this? I'm thinking that at worst it will provide a lower output voltage that may not be sufficient, but I have no experience of replacing these.Sadly, the Ukranian company never got back to me.

author: wraper
author_rank: Unknown
timestamp: March 21, 2018, 03:44:53 pm
content: AFAIK 1J.26061.021 outputs slightly lower voltage. It is used on slightly different version of this PCB. It's safe to use, just max brightness may be slightly lower.

author: WaveyDipole
author_rank: Frequent Contributor
timestamp: March 21, 2018, 07:37:19 pm
content: Do I need to replace both so as to balance brightness across the screen? (I did order a spare). I will try the one first anyway and see whether it works and what it looks like. Thanks.

author: wraper
author_rank: Unknown
timestamp: March 21, 2018, 07:54:32 pm
content: Quote from: WaveyDipole on March 21, 2018, 07:37:19 pmIt does not matter. Many edge lit LCDs are lit only by one lamp / LED strip on one edge and work completely fine.

author: WaveyDipole
author_rank: Frequent Contributor
timestamp: March 22, 2018, 10:27:28 am
content: Well, I replaced the faulty inverter transformer and that did indeed solve the problem. I re-assembled it and then ran it connected to my laptop for a few minutes without any problem. If there is a reduction in brightness then it is difficult to discern.Wraper, thank you for helping out with this and to all who contributed comments. I am glad that I had a go at repairing this monitor as it is a working unit once again rather than going to landfill, and I have learned something along the way.