Westinghouse W1603 TV Repair - Page 1
Forum section: electronics / repair

author: Fisher77
author_rank: Regular Contributor
timestamp: December 15, 2016, 01:55:17 am
content: Ok, here is the rub. The power line going into my parents house got zapped by a lighting bolt. It knocked out 3 tv's, a satellite box, satellite dish components, 1 computer, 1 light fixture, 1 light switch, 2 GFCI socktes, and threw just about every breaker in the house. In other words, it did a number on the house. My dad compared the ensuing thunder crack to the sound of a 155mm Howitzer shell impacting the earth. He would know(1st Calvary Division '66 to '67). I am hoping to get some help with this tv, and possibly the other 2 tv's to help take the burden of my parents pocket book. I figure the mobo got zapped on the computer, so it is probably toast, but well, I'll crack it open anyhow to take a look.This Westinghouse is the first of the 3 tv's. Here are the voltages on the power supply output:+12V = 0V+12V = 0VGNDGND+3V = 0V+5V = 0VGNDGNDOn/Off = 0VDIM = 0VWith those voltages listed I am pretty sure this power supply is graveyard dead. I have checked everything I know how to check on it. There is one diode, D909, that I am getting .018 both ways when I check using the diode check on my DMM. With that being said, I assume it is a Zener by the way it looks. But I may be wrong, It is in the red box in the pic. I have checked all of the resistors, and the diodes, and caps on the bottom that I could without pulling them out of circuit. I have really come to hate most smd components because unless you work with them alot, then 3/4's of the time you dont even know what the hell it's value is. The resistors are usually marked well, why they cant do the same with the caps and diodes is beyond me. The MOSFET Q901 has voltage to the drain. I pulled it off of the board, and checked it. It is switching as it should. That is about all I can do up to this point. Any help with this would be greatly appreciated!

author: Fisher77
author_rank: Regular Contributor
timestamp: December 15, 2016, 04:49:18 am
content: Here are the pics of the power supply board:Third pic shows the diode I was talking about.https://i.imgsafe.org/21fc437702.jpghttps://i.imgsafe.org/21fc86dcc7.jpghttps://i.imgsafe.org/21fcb47858.jpghttps://i.imgsafe.org/21fcfd2808.jpghttps://i.imgsafe.org/21fd442c6e.jpg

author: pyroesp
author_rank: Regular Contributor
timestamp: December 15, 2016, 04:17:51 pm
content: Hello Fisher77,Well that sucks... Hopefully more knowledgeable people than me will be able to help you out.From the looks of the components on the underside of the PCB, D909 is a "simple" diode. Look all the way left, right next to the connector CN902, there's a diode labelledZD920, which I guess stands forzenerdiode.You mention that you have power on the drain. The next step should be to "chop" the voltage (see block diagram below). An optocoupler (IC903) should be usedto drive the gate of the MOSFETas a feedback for a PWM IC which drives the MOSFET gate. Does the optocoupler still work ?Does it receive a PWM (or other square wave) signal ?(from wikipedia)EDIT1:It might be interesting for you to find and watch some SMPS repair videos. They're always helpful and might point you to the right direction.EDIT2:If you can not get it to work, you might be able to find one onebayoraliexpress.Let's just hope it's only the power supply that blew up and the main processor of the TV is ok.

author: Fisher77
author_rank: Regular Contributor
timestamp: December 15, 2016, 07:11:46 pm
content: The optocoupler is still good, I pulled if from the board and tested it a little bit ago. The collector of the optocoupler is connected to pin 2 of IC901. Pin 5 of IC901 is connected to the gat of the MOSFET. IC901 is a LD7575PS.As far as the PWM to the optocoupler, I do have a scope. Its a older crt that I am still learning to use. If you can tell me where/how to connect it, I will check for the signal.Edit: I noticed I have continuity between all the pins on the T901. Also have continuity between the positive side of C930 and all the pins on T901. Is this normal? Dont seem right to me.I have outlined all the pins in the pichttps://i.imgsafe.org/2eefae445a.jpg

author: pyroesp
author_rank: Regular Contributor
timestamp: December 15, 2016, 08:25:51 pm
content: What model oscilloscope do you have ?T901 is your output transformer, which is basically a wire.

author: Fisher77
author_rank: Regular Contributor
timestamp: December 15, 2016, 08:50:12 pm
content: Tektronix 2205

author: pyroesp
author_rank: Regular Contributor
timestamp: December 15, 2016, 09:44:40 pm
content: My bad I said something stupid. The optocoupler is just used as a feedback of the output voltage to the PWM IC, it does not drive the mosfet.You should be able to measure the voltage on the LED side of the optocoupler with a multimeter.If you want to know how to use your oscilloscope:Here's a video Dave made on a Tektronix 2225, which is almost identical to the 2205:Here's another one on how NOT to blow your oscilloscope up:

author: Fisher77
author_rank: Regular Contributor
timestamp: December 15, 2016, 10:11:52 pm
content: Thanks for the videos. I will definitely watch them, prolly more than once. As for the optocoupler, it has 0V on the LED side, and 0V on the emitter and collector.

author: pyroesp
author_rank: Regular Contributor
timestamp: December 15, 2016, 10:36:54 pm
content: IC901 looks like it's the mosfet driver. Try to find it's datasheet and see how it works/turns on. Can't see the part number of IC901 on the pictures.

author: Fisher77
author_rank: Regular Contributor
timestamp: December 15, 2016, 10:46:00 pm
content: It is a LD7575PS. Here is a link to the datasheet, if you would like to have a look:https://lib.chipdip.ru/923/DOC000923326.pdfI traced the tracks, and it is definitely looks like it is supposed to drive the mosfet.Here is what I am measuring on the IC:1:0V has resistor to ground2:0V3:0V4:GND5:0V6:11.6VDC7:NC8:145VDC

author: pyroesp
author_rank: Regular Contributor
timestamp: December 16, 2016, 12:17:27 am
content: Pin 5 should send a PWM signal to the gate of the MOSFET for it to turn on and off, which will generate an AC voltage on the transformer.Something you could check is the resistor to ground on pin 1 (RT). From the datasheet, this resistor selects the frequency, see p.10. But also, if it were to short (RT to ground) or break (RT floating), then the IC goes into fault protection.Other than that, I'd guess it blew up. You could find one on ebay for cheap.

author: Fisher77
author_rank: Regular Contributor
timestamp: December 16, 2016, 06:54:53 pm
content: Resistor is good. I guess I will order a new LD7575PS , and see if that does it.

author: Fisher77
author_rank: Regular Contributor
timestamp: December 17, 2016, 02:26:10 am
content: Thanks for the help pyroesp. I ordered a new LD7575PS today. Be a couple of weeks before I see it. When it gets here and I get it in, I will post back.

author: pyroesp
author_rank: Regular Contributor
timestamp: December 17, 2016, 04:09:08 am
content: Glad to help, altough I would have liked someone else to pitch in and correct my stupid mistake(s?)or give other tips.In the mean time, let's see what's wrong with the 2 other TV's. You should be able to apply the same troubleshooting.

author: Fisher77
author_rank: Regular Contributor
timestamp: December 18, 2016, 12:35:48 am
content: On the second tv I found a blown MOSFET, and a blown Diode. I had to order them as well. Hopefully that will be all that is wrong with that one. The third tv I have yet to find a problem. I will post pics of the PS as soon as I get a chance.

author: Fisher77
author_rank: Regular Contributor
timestamp: December 18, 2016, 09:59:07 pm
content: Here are pics of the third tv's PS board. It is a Sony Model KDL-32L5000Here are the voltages:P ON = 0VAC DET = 3.3VSTBY = 3.3VUNREG 15V = 0VREG 12V = 0Vhttps://i.imgsafe.org/70006bb981.jpghttps://i.imgsafe.org/7001003596.jpghttps://i.imgsafe.org/6fffd634ea.jpghttps://i.imgsafe.org/70022d3371.jpghttps://i.imgsafe.org/7002916035.jpghttps://i.imgsafe.org/701d1871f9.jpgNow what would happen if I jumped the 3.3 STBY to the P ON?Is it possible that would turn the PS on and I would see the other voltages indicating a problem on the main board of the TV?

author: pyroesp
author_rank: Regular Contributor
timestamp: December 18, 2016, 11:16:32 pm
content: I think I found the schematic while googling a bit (click the download button):http://www.electronica-pt.com/esquema/func-startdown/29241/Check if the PCB matches the schematic, always helpful for troubleshooting if it is.The fact that the Power On comes from the controller board, means there's probably something wrong there.Maybe you could check the controller board to see how it sends the Power On signal (probably from CPU).I think you can try to bypass the controller board, but try to check the components on the Power On circuit first to make sure you have no short to GND.

author: Fisher77
author_rank: Regular Contributor
timestamp: December 20, 2016, 12:22:59 am
content: Ok, I checked the PS over. I found nothing wrong. I finally jumped the stby 3.3v to the ps_on pin on the power supply while I had my meter connected to the 12V regulated output. The power supply kicked on and the meter was reading 12.3V. I then checked the 24V output on the other side of the power supply that supplies voltage to the back light inverter, and it read 24.4V. Looks like the power supply is good. I will have to do my best to trace out the ps_on, and stby circuits on the main control board. I will post some pictures of it in a bit.Here are the pics:https://i.imgsafe.org/8a34203af3.jpghttps://i.imgsafe.org/8a346e936e.jpghttps://i.imgsafe.org/8a347b8547.jpghttps://i.imgsafe.org/8a34bb9083.jpg

author: KhronX
author_rank: Frequent Contributor
timestamp: December 21, 2016, 11:47:00 am
content: Aaaaand where's someone supposed to get the content of whatever (E)EPROMs and flash chips, hmm?I doubt anything's gonna start without something to boot (from)Never been a fan of the shotgun approach...Quote from: aquamon on December 21, 2016, 10:43:25 am

author: Fisher77
author_rank: Regular Contributor
timestamp: December 22, 2016, 01:59:50 am
content: Quote from: KhronX on December 21, 2016, 11:47:00 amAnd will a EEPROM prevent the TV from turning on?I know one damn thing, I can jump the 3.3V stby to the ps_on, and turn the tv on with the on/off button on the side of the tv.

author: Fisher77
author_rank: Regular Contributor
timestamp: December 22, 2016, 04:00:00 pm
content: Quote from: aquamon on December 22, 2016, 11:39:37 amNo snow. It powers on the the startup screen with "no signal" on the screen. I will have a look at the 5v rail and post back. Thanks auqamon.Quote from: aquamon on December 22, 2016, 11:51:52 amDidnt intend to step on your toes. I was simply asking if the eeprom will keep a tv from turning on. I dont know what all the eeprom does. I have fixed a few tv's in the past, but they were always a power supply issue, mostly blown caps. This is the first time I have dealt with an issue on the main board. I would like to be able to fix it for my parents, and at the same time learn a little more about how all this works.

author: KhronX
author_rank: Frequent Contributor
timestamp: December 22, 2016, 04:35:17 pm
content: If it gets as far as driving the LCD panel and backlight enough to say "no signal", at least to me, means that most of the essential blocks are working just fine, including the main processor.Does it say that, regardless of the selected input? Or only on the TV/cable input?Quote from: Fisher77 on December 22, 2016, 04:00:00 pmMost (if not all) LCD TV's are basically an all-in-one (stripped-down) computer nowadays. They have a processor, and they boot an operating system from an on-board memory chip (usually flash-based) - in some cases a version of Linux, in the case of some smart-tv's it's a flavour of Android, etc.The EEPROM is another form of electronic data storage, but more often quite small in size, and it usually holds stuff like calibration data, or system ID stuff - small-sized but occasionally essential data for the functioning of the whole systemQuote from: Fisher77 on December 22, 2016, 04:00:00 pm

author: Fisher77
author_rank: Regular Contributor
timestamp: December 22, 2016, 05:58:32 pm
content: Thanks for the explanation of the eeprom KhronX. I had seen people talking about it on forums, but never knew what it did.Quote from: KhronX on December 22, 2016, 04:35:17 pmI just checked, and it does say that on all inputs. I hooked a dvd player to all the inputs, with the exception of the HDMI inputs of course, and it showed the movie I had in the dvd player.

author: KhronX
author_rank: Frequent Contributor
timestamp: December 22, 2016, 06:31:51 pm
content: Ok, now i'm getting confusedOn one hand, "it does say that on all inputs", but on the other hand, "it showed the movie I had in the dvd player" on the s-video / scart / composite (?) inputs.So which one is it?

author: Fisher77
author_rank: Regular Contributor
timestamp: December 22, 2016, 07:13:32 pm
content: Ok, I went through all the inputs, AV, composite, hdmi, tv/cable, and PC and it had the "no signal" on all of those selections.Then I hooked up a dvd player and checked the AV, composite, and tv/cable inputs with a movie playing in the dvd player, and saw the movie on the screen.

author: SeanB
author_rank: Super Contributor
timestamp: December 22, 2016, 07:25:28 pm
content: That then exonerates all the digital side, leaving the tuner alone. Is the system set correctly, best is to change to another system, then scan again, then change back to the country system you are in and rescan. That way, if it was eeprom data errors it will be written correctly, and if not then the tuner itself has died, probably from a high voltage zap on the antenna input.Easy enough to change the tuner with a donor from another set, but if it has died you probably are better off getting an external cable box or satellite receiver and using HDMI to connect.

author: KhronX
author_rank: Frequent Contributor
timestamp: December 22, 2016, 07:26:57 pm
content: In that case, it sounds to me like it works as well as you can hope.When you've got nothing connected to an input, would you expect it to display anything else than "hey, i'm getting no signal at the input you've selected" ?Or is the tuner section still not working?

author: Fisher77
author_rank: Regular Contributor
timestamp: December 22, 2016, 07:33:38 pm
content: Well when hitting the chanel up or down buttons, it does not change the channel, but without an antenna or cable input, it probably wont change channels. The big problem is the only way to get it to turn on is by jumping the 3.3v stby to the ps_on at the power supply.

author: KhronX
author_rank: Frequent Contributor
timestamp: December 22, 2016, 07:41:09 pm
content: Silly question perhaps, but is the connector to the button-board, and the remote-sensor respectively, plugged in?And/or is there a supply voltage present on any of the pins of those connectors?Quote from: Fisher77 on December 22, 2016, 07:33:38 pm

author: Fisher77
author_rank: Regular Contributor
timestamp: December 22, 2016, 07:49:06 pm
content: Quote from: KhronX on December 22, 2016, 07:41:09 pmYes both plugged in, I checked, and both do have voltage. Input button, menu, and volume buttons on the side of the tv all work. Unfortunately, I do not have the remote in my possesion to test it.I also removed the jumper. Even though the power supply is providing the 3.3v stby, the stby led on the front of the tv is not lit up.

author: pyroesp
author_rank: Regular Contributor
timestamp: December 22, 2016, 11:03:13 pm
content: Quote from: aquamon on December 22, 2016, 10:39:25 pmWell done dude, go ahead pat yourself on the back.@Fisher77: from the silkscreen on this image :https://i.imgsafe.org/701d1871f9.jpg, you don't seem to have a 5VDC output. Unless the 5VDC is regulated on the CPU board ... ?@Aquamon: This is the 3rd non working TV. Not the same as the one in the first post.

author: Fisher77
author_rank: Regular Contributor
timestamp: December 23, 2016, 01:54:25 am
content: 12V from the ps gets regulated down to 5 on the main board, or at least thats what it looks like in the manual.Service manual is here. Mine is the one in the red box in the pic:http://elektrotanya.com/?q=showresult&what=Sony%20KDL-32L5000&kategoria=&kat2=all

author: Fisher77
author_rank: Regular Contributor
timestamp: December 23, 2016, 02:40:34 am
content: It has the 5 volts on the main board

author: KhronX
author_rank: Frequent Contributor
timestamp: December 23, 2016, 09:34:49 am
content: I kinda figured as much. I'm willing to bet big bucks the tv wouldn't start and be able to display a DVD playing back, without the 5v rail being presentQuote from: Fisher77 on December 23, 2016, 02:40:34 am

author: Fisher77
author_rank: Regular Contributor
timestamp: December 23, 2016, 02:22:18 pm
content: Quote from: KhronX on December 23, 2016, 09:34:49 amRight, and I would not bet against you on that one.I thought of something while I was sitting here this morning. I was testing that with the jumper in. So the power supply was supplying the main board with the 12V. If I pull the jumper out, the power supply turns off, 12V is gone because the power supply is off, and the 3.3V stby drops to .4V with the main board cable connected to the power supply.Unplug the cable from the power supply to the main board and the stby remains at .4V.Unplug the power supply from the mains for a few minutes, plug it back into mains, and the stby is back to 3.3V. Reconnect the cable from the power supply to the main board, the relay on the power supply clicks on, then clicks off, and then the stby drops back down to .4V, and remains there until the power supply is disconnected from mains again for a few minutes.I hope the way I explained that is understandable.What the hell is going on here. Is it a power supply issue, a main board issue, or a little of both?

author: KhronX
author_rank: Frequent Contributor
timestamp: December 23, 2016, 04:27:43 pm
content: Could something be overloading / dragging down the 3.3v stand-by rail?Here's something (else) to try - if you keep the power supply plugged in, but the mainboard disconnected, does that stand-by rail stay at 3.3v, even after the time interval it would drop out if the mainboard was hooked up?

author: pyroesp
author_rank: Regular Contributor
timestamp: December 23, 2016, 04:46:59 pm
content: Quote from: KhronX on December 23, 2016, 04:27:43 pmFrom previous posts it looked like the 3.3V was stable, but it looks like once the 3.3V has been loaded down to 0.4V it can't get back up to 3.3V as stated here:Quote from: Fisher77 on December 23, 2016, 02:22:18 pm@Fisher77: You could try to load the 3.3V down with a small value resistor (maybe a pot to have some control over the current drawn) and check whether the 3.3V is stable or not.If what Aquamon stated about the 5V is true, then the 3.3V going to the Power On is not controlled by the CPU. The CPU needs 5V, and 5V is only regulated from the 12V going out of the power supply board.Whatever is linking the standby 3.3V supply to the power on might be shorted to ground or loading the 3.3V rail down on the main board.

author: KhronX
author_rank: Frequent Contributor
timestamp: December 23, 2016, 06:03:22 pm
content: Oh grow up!...

author: KhronX
author_rank: Frequent Contributor
timestamp: December 23, 2016, 06:46:39 pm
content: Funny you should say that - if anyone "feels" like they're trolling, it's actually you

author: pyroesp
author_rank: Regular Contributor
timestamp: December 23, 2016, 07:07:50 pm
content: Why are you so butthurt ? Is it because someone did not do what you asked ?Quote from: aquamon on December 23, 2016, 06:41:26 pmI can't see a download link on the website you gave, all it shows is "...processing...". I've had the webpage open for awhile and never got a link.As far as my intentions are, I'm trying to help.It's true I might not have your experience, but at least I have the humility to not call (or insinuate) I'm an expert and ordering people what to do instead of explaining why they should do something.Is it not so that you don't have 5V unless the 12V is present on the main board ?The 12VDC is only generated when OP jumped the 3.3V to the P_ON pin. So this, and the last post from OP, leads me to believe there's something wrong with the 3.3V.Is that not the next step to do? Try and solve the 3.3V rail ?I don't see the logic in jumping straight to checking the 5V or EEPROM(s).This is a forum, people have opinions and ideas that might differ from yours. If you can't live with that, then leave. Instead, you behave like a kid who couldn't get what he wanted.

author: pyroesp
author_rank: Regular Contributor
timestamp: December 23, 2016, 09:07:43 pm
content: I managed to get the pdf through my phone. Why it wouldn't give me a link on my laptop I don't know.QuoteAll 3 tv's have been damaged by a lightning strike.From the schematic the power on goes through transistor Q210. There's a test point TP001 you might want to measure.If it's high then the transistor should put the 3.3V (minus the Vce) on the power on.

author: pyroesp
author_rank: Regular Contributor
timestamp: December 23, 2016, 11:13:03 pm
content: True, everyone values their time how they want.I don't know if OP has better things to do, but he said he wanted to keep the cost to a minimum, so I don't see the harm in checking a few more things before giving up and buying a new main board.Does the tuner have a part number on it ? If it's fried, how much would a new tuner cost ? (Haven't checked this in the manual yet, will check that now)

author: Fisher77
author_rank: Regular Contributor
timestamp: December 24, 2016, 12:45:12 am
content: Quote from: KhronX on December 23, 2016, 04:27:43 pmTried this and the stby stayed at 3.3V stayed for over an hour. That is as far as I got today before being drug away for the glorious Christmas shopping.

author: Fisher77
author_rank: Regular Contributor
timestamp: December 24, 2016, 12:51:15 am
content: Quote from: pyroesp on December 23, 2016, 11:13:03 pmOff of work for the next 2 weeks. I don't have anything better to do. If it comes to ordering a board I will, but why not try to repair the thing, and learn something in the process.Question: Is the tuner going to prevent the TV from turning on?

author: KhronX
author_rank: Frequent Contributor
timestamp: December 24, 2016, 02:17:01 am
content: I'm sorry for asking, but what exactlyISyour problem?Is anybody holding a gun to your head and keeping you "hostage" on these "dead" forums?If this is "taking too long", consuming mental energy, and your time is oh-so-precious... What exactly are you doing here again?It's Fisher77's TV, it's his time, it's his energy, he's free to do whatever he pleases. And i'm pretty sure he doesn't owe you repairing this in whatever arbitrary time-frame you decidedIf something doesn't please you here, you're free to leave and find other groups of people who are more worthy of your time and energy - we obviously are not, and don't even come close to your standardsQuote from: aquamon on December 24, 2016, 01:29:58 am

author: Fisher77
author_rank: Regular Contributor
timestamp: December 24, 2016, 03:19:06 am
content: Quote from: aquamon on December 24, 2016, 01:29:58 amI did not realize that I had a set schedule that I needed to follow there BOSS. Pardon me for not updating this thread every five minutes for you. You know at this particular moment this is not all that I have to do, especially with Christmas the day after tomorrow. After the Christmas holiday, I will have plenty of time to spend on this.Quote from: aquamon on December 24, 2016, 01:29:58 amMaybe if you would take the time to read all of the posts you would see that the brand, and model number were revealed in post #15 of this thread.Quote from: aquamon on December 24, 2016, 01:29:58 amGood for you, glad you never ordered a board. Neither have I, and this is not the first tv I have fixed, yet this is the first one that there has been a issue on the main board, so I simply posted here for help. So far, the only help you have offered me is to just throw the damn thing away, or chunk parts at it without trying to diagnose the problem. Furthermore it must be nice to have a pocket book thick enough to just throw a TV in the can, and run out and buy a new one. You know not everyone is in that postition.Quote from: aquamon on December 24, 2016, 01:29:58 amThere again I did not realize I had to stick to your schedule. As mentioned by KhronX I am not holding you here. As far as your mental energy is concerned, I recommend you make an appointment with your psychologist, take some meds, and get over it. It is my time, and if I feel like spending a month on it I will. If you feel it is taking tooooo looooong, then feel free to move it on down the line. I did not ask you to post on my thread. You might also want to reconsider if you want to be part of a forum or not. I can assure you that the behavior you have provided us here on this thread is not going to get you any brownie points on any forum that I know of.Quote from: aquamon on December 24, 2016, 01:29:58 amMake sure the screen is good.Do you really think I would be spending this much time trying to fix the damn thing if the screen was not good. Would you like to see a picture as proof??? This is further proof that you have not bothered to read all of the posts. If you would have read them, you would see that I had a DVD player, playing a movie, connected to the TV in post 28.I agree with KhronX. You are free to go. Go find yourself another group of know it alls to hang out with. Doesn't seem to be enough professionals around here for you. Before you join another forum though, I suggest you make sure they want to stick to your time constraints there , or your mental energy will be totally drained.

author: pyroesp
author_rank: Regular Contributor
timestamp: December 24, 2016, 04:50:31 am
content: Quote from: Fisher77 on December 24, 2016, 12:51:15 amWell you already know the TV works by jumping the 3V3 to the power on.I wouldn't think the tuner, which is your RF receiver for your analog signal/antena, could prevent the TV from working.From the block diagram on p.26 of the manual, you can see the tuner in the upper left corner (RF in).None of the arrows going out of the tuner go to something important like the regulator ICs, only to some analog or digital signal processing block.

author: Fisher77
author_rank: Regular Contributor
timestamp: December 24, 2016, 05:12:37 am
content: Thats what I see to. I am still trying to fathom how a tuner is going to keep a tv from powering on.I was reading the previous post you made about using a low value resistor to load the 3.3V. What value do you think I should use?

author: Monkeh
author_rank: Super Contributor
timestamp: December 24, 2016, 05:57:45 am
content: Quote from: Fisher77 on December 23, 2016, 02:22:18 pmSomething connected to the 3.3VSB rail is either drawing excessive current, or the power supply is unable to handle the normal current it does want. The main 3.3V rail is generated by a 5A(!) capable LDO from the +5V rail, which itself is generated from the +12V rail by a buck converter. Clearly the LDO is stiff enough to handle whatever demand is placed upon it.Find L215 (should be near IC204, the LDO) and measure the voltage across it. It's not exactly a current shunt, but it may serve the purpose. It's rated for 2A at best, so if you see upwards of 20mV across it, that's a pretty clear indicator of a fault. If it's a very low value I'd suspect a weakness in the power supply.As far as loading the standby rail goes, somewhere in the 20-50ohm region should be enough to determine if the supply is weak - it should have no problem with supplying such a load with no notable droop. Be warned typical small resistors will get quite hot, quite fast, but they'll do the job.And for the tuner, it does have a few connections running around the place - half of which are AC coupled and the other half have resistors inline which should prevent pulling the standby rail down that hard. Any damage via that route is in the main IC.

author: pyroesp
author_rank: Regular Contributor
timestamp: December 24, 2016, 06:21:46 am
content: Quote from: Monkeh on December 24, 2016, 05:57:45 amThe main 3.3V is only generated after the 3V3SB is sent back on the Power ON line and the reg 12VDC is sent from the power supply board to the main board.I'd think it's something on the standby voltage circuit that's pulling the voltage down, like maybe C209 or C210 ?

author: Monkeh
author_rank: Super Contributor
timestamp: December 24, 2016, 06:29:19 am
content: Quote from: pyroesp on December 24, 2016, 06:21:46 amIf C209 or C210 were at fault the rail would most likely stay down. It apparently maintains fairly normal voltage once the supply is started and the TV running (I'm not sure how the TV could operate if it didn't, seeing as it powers the main oscillator and holds the supply on..), which means either it's being held up by the main rail or switched out in favour of the main rail (internally to the MT5386). Either way, the main rail will show the current loading if that's the issue.

author: Gyro
author_rank: Super Contributor
timestamp: December 24, 2016, 10:47:12 am
content: Well, isn't the world a calmer place this morning...Just reading back through the last page or so - post deletions have made it look as if people have been makingtype responses to perfectly reasonable suggestions.New readers of the thread need to be aware that a large number posts have been deleted and so there is some loss of context! (Applies to the Dumpsterdive TV repair thread too).

author: aquamon
author_rank: Newbie
timestamp: December 24, 2016, 01:48:45 pm
content: http://forum.allaboutcircuits.com/threads/sony-kdl-32l5000-will-not-turn-on.130583/#post-1075476This hasn't been fixed from September...

author: KhronX
author_rank: Frequent Contributor
timestamp: December 24, 2016, 02:03:14 pm
content: You justhadto jinx it, didn't you?Quote from: Gyro on December 24, 2016, 10:47:12 amQuote from: aquamon on December 24, 2016, 01:48:45 pm

author: pyroesp
author_rank: Regular Contributor
timestamp: December 24, 2016, 02:30:57 pm
content: Quote from: aquamon on December 24, 2016, 01:48:45 pmI don't see why that matters. Someone came here because of an issue. As an electronic forum we try to help the best we can (at least that's my vision).Only OP knows what happened between then and now.The fact is he's still with non-working TVs and doesn't want to and might not be able to spend money to buy 3 new TVs.If it were just one, maybe I would agree to buying a new one. But it's not one, it's 3 new TVs.I can't complain about my job, but even with it, buying 3 new TVs would set me back quite a bit too.Anyways...Let's see what OP can find by doing what Monkeh's suggested.

author: cheeseit
author_rank: Regular Contributor
timestamp: December 24, 2016, 02:47:54 pm
content: This is the first troll I've encountered on this board. Was kinda fun but I'd rather be without so in the spirit of Christmas and all, please just stop. All those post deletions also ruins the flow and gives the wrong impression of this forum so I hope the mods just ban/delete the user and leave their posts in the future.

author: Fisher77
author_rank: Regular Contributor
timestamp: December 24, 2016, 02:59:53 pm
content: Quote from: cheeseit on December 24, 2016, 02:47:54 pmI agree. Just love his signature to. He is a real class act

author: KhronX
author_rank: Frequent Contributor
timestamp: December 24, 2016, 03:06:33 pm
content: "Welcome to the club"...Quote from: Fisher77 on December 24, 2016, 02:59:53 pm

author: Fisher77
author_rank: Regular Contributor
timestamp: December 24, 2016, 05:32:33 pm
content: Quote from: pyroesp on December 23, 2016, 09:07:43 pmVoltage on TP001 with the 3.3V jumped to ps_on is 0.5V, without the jumper it is 42.3mV.Quote from: Monkeh on December 24, 2016, 05:57:45 amWith the 3.3V jumped to ps_on, L215 has 14.4mV across it. Without the jumper, L215 has 0.00V across it.I loaded the 3.3V with a 39ohm resistor. The voltage remained at 3.3V. Never dropped. The resistor did not get hot, just a little warm, I could hold it between my fingers and barely feel it was getting warm. Dont know if that means anything.

author: Monkeh
author_rank: Super Contributor
timestamp: December 24, 2016, 05:47:52 pm
content: Quote from: Fisher77 on December 24, 2016, 05:32:33 pmAt least 1.4A. That's enough to at least make me suspicious.QuoteI'd call your power supply healthy enough.So the problem is most likely a component on the +3V3SB rail being faulty - there's not much there. A couple LEDs, the switch board, and.. the main processor.If you happen to have a power supply with some gusto (a spare PC PSU perhaps), feed the 3V3SB rail with it (no need for the main power supply board) and see what sort of current is drawn and what gets hot. Money's on IC401.

author: Fisher77
author_rank: Regular Contributor
timestamp: December 24, 2016, 06:07:26 pm
content: I have a spare PC supply. I will hook it up when I can, and post back. Thanks for all the help guys.

author: Fisher77
author_rank: Regular Contributor
timestamp: December 25, 2016, 04:36:02 am
content: Quote from: Monkeh on December 24, 2016, 05:47:52 pmJust to make sure I am on the same page, you want me to feed the 3V3 stby pin on the main board with the CPU PS 3V3 output. Is that correct?If that is correct, the IC401 got warm, I would not call it hot, just enough to tell there was a temp change. The current draw was .55 amps.

author: Monkeh
author_rank: Super Contributor
timestamp: December 25, 2016, 04:41:50 am
content: Quote from: Fisher77 on December 25, 2016, 04:36:02 amI don't have any numbers for that chip, but to run an oscillator and wait for a startup command, that seems hugely excessive. I'm willing to bet it's broke.If anyone can figure out a current path outside IC401, though..

author: Fisher77
author_rank: Regular Contributor
timestamp: December 25, 2016, 06:40:13 pm
content: I pulled the main board out of the tv. Laying on my bench I fed 3v3 to the stby pin of CN201. I was just probing around checking voltages and decided to check the voltage on CN4201 that goes to the button module on the side of the tv. I noticed I have 2.7 volts on pins 5,4 and 3 of that connector. Now pin 5 looks to be the 3.3 volt supply to the module. Pin 4 is for the power button. And pin 3 is the ADC_IN2(whatever that is). Now is there supposed to be voltage on pin 4, without pressing any button? ( Pic attached)The reason I ask is that I also noticed that the ps_on pin of the CN201 connector that goes to the PS board has 2.7 volts when there is nothing telling the main board to power on the tv.Is this conformation that IC401 is toast?And if the ps_on pin is constantly being fed voltage, why is the tv not just turning on when it is plugged in?

author: Monkeh
author_rank: Super Contributor
timestamp: December 25, 2016, 07:44:27 pm
content: The power on signal is active low, it expects it to be taken down to ground.2.7V is strange, that should be at 3.3V.

author: pyroesp
author_rank: Regular Contributor
timestamp: December 25, 2016, 07:54:08 pm
content: Pin 4 is connected to +3V3SB through pull-up resistor R4202.

author: Fisher77
author_rank: Regular Contributor
timestamp: December 26, 2016, 12:40:07 am
content: Quote from: Monkeh on December 25, 2016, 07:44:27 pmI thought 2.7v was strange to.

author: Fisher77
author_rank: Regular Contributor
timestamp: December 26, 2016, 12:42:54 am
content: Quote from: pyroesp on December 25, 2016, 07:54:08 pmMissed that this morning. Tired eyes I guess.

author: Fisher77
author_rank: Regular Contributor
timestamp: December 26, 2016, 07:13:58 am
content: I was checking some more on this main board and found something else that seems odd to me, but it could be normal. When I am feeding the stby with 3.3 volts I still have the 2.4 to 2.7 volts on the P ON ping. But I also noticed I am seeing 1.4 volts on the regulated 12V pins as well. Is that normal?Something else I noticed is when I have the meter on continuity(buzz) and probe the 3.3V stby pin and the ground pin the meter buzzes away, never stops. I know that setting pretty much gets you from point A to B, but curious if that should be happening. Certainly dont happen on the PS_ON pin, REG 12V pins, or the UNREG 15V pins.I did ohm from the stby pin to ground and it measured 23.4 ohms.

author: Monkeh
author_rank: Super Contributor
timestamp: December 26, 2016, 04:21:05 pm
content: No, it really should not measure that low.Something, almost certainly IC401 (there's pretty much nothing else connected directly to the rail) has a major internal fault. It's likely not repairable.

author: Fisher77
author_rank: Regular Contributor
timestamp: December 26, 2016, 05:50:51 pm
content: I do beleive you are absolutely right Monkeh. Looks like the only fix is to get another main board. Shopjimmy has none. Found plenty on ebay, but getting one off of ebay that is good can be a challenge in itself. I have read the stories of it taking 3 or 4 boards before a person gets a good one.A big thanks to everyone who has helped mo out with these two tv's!!I will post back with the resuslts when I get the part installed for the Westinghouse.Next will be an HP computer, but I figure the mobo is probably toast. Only way to find out is to crack it open and see. I will start a new thread for that one when I get to it.

author: Fisher77
author_rank: Regular Contributor
timestamp: January 02, 2017, 09:46:08 pm
content: Ok, on the second tv, its a Vizio that I found a blown FET and Diode on, I also found a blown resistor. It is a 0.27 ohm resistor. I have found a 0.24 Ohm resistor on another scrap board I had lying around.Will 0.24 ohms be close enough to 0.27 ohms, or do I need to order the 0.27 ohm resistor? They are 5% resistors.I have also located a 0.35 ohm, if more would be better than less.

author: KhronX
author_rank: Frequent Contributor
timestamp: January 03, 2017, 01:12:41 am
content: That would depend entirely on where it is, on the schematic / what role it has in the circuit.Let me guess - it's on the primary side, between the source of the flyback switching MOSFET and ground?With the blown FET, that makes sense.I'd also expect a potentially blown PWM controller chip, so be mentally prepared for that too.Either one would be fine, although i'd lean towards the 0.24 one.

author: Fisher77
author_rank: Regular Contributor
timestamp: January 03, 2017, 01:34:04 am
content: Quote from: KhronX on January 03, 2017, 01:12:41 amYou are correct KhronX. It is between the source ans ground. Guess I should have pointed that out.One other option is to parallel a 1.5ohm with a .35 ohm for 0.28 ohms. Plenty of room on the board for it.I am sure your prolly right about the PWM controller chip. Wouldnt surprise me on bit.

author: KhronX
author_rank: Frequent Contributor
timestamp: January 03, 2017, 08:31:47 am
content: I wouldn't lose any sleep over that. With 5% tolerances, the 0.24 one could actually be as high as 0.252, and the 0.27 could be as low as 0.257And besides, i quite doubt the tv's (normally) running anywhere near what the PSU can provide, so there's some leeway there, as well.These things are rarely (if ever) designed "right on the edge" - unless we're strictly talking cost

author: Fisher77
author_rank: Regular Contributor
timestamp: January 03, 2017, 04:26:31 pm
content: Well I installed the new FET and the .24 resistor, plugged it in, and zap, blew the FET and the resistor immediately. I will start a new thread for this one.

author: KhronX
author_rank: Frequent Contributor
timestamp: January 12, 2017, 09:14:42 am
content: If i didn't type it out in this thread, i at least thought it - if the FETandthe source resistor are blown, chances are good the PWM controller's gone as well.I've experienced that first-hand (including blowing the replacement FET) once or twice myself

author: Fisher77
author_rank: Regular Contributor
timestamp: January 12, 2017, 08:53:20 pm
content: Well here is the Westinghouse up and running again. Replaced IC109. It is a LD7575 PWM.I appreciate everyones help with it.

author: Fisher77
author_rank: Regular Contributor
timestamp: March 03, 2017, 04:57:39 pm
content: Quote from: Fisher77 on December 26, 2016, 05:50:51 pmOk, I finally got back to the Sony tv. I replaced the main board, and it still will not fire up, and has no stanby light. Anyone have any suggestions?