I was a TV engineer from '56 and retired just as flat screens were coming in. Its nice to see you repairing down to component level, as we did. Very good video 😊
@@michaeldranfield7140... The problem also is repairing a CRT TV today also. Even having a working digital signal converter to analog signal box, a fixed CRT of say $50 for parts and labor (as a new HDTV of CRT screen size can be $200-$350 in the U.S.) there is risk of further breakdowns of electronic components barely getting by. Even nostalgic computer gamers saying they are spending $200+ in the U.S. on nostalgic old CRT TVs now getting 16+ years old as the beyond warranty last engineering designed day of that TV for lasting longer like a brand new TV. Having to buy a $200 nostalgic 32 inch TV max, 16+ years old, is not worth the risk as figuring out an advantage of buying a new TV of High Definition like this fix on this RU-vid video at hopefully less than $75 in the U.S. as a brand new 55" of this same model is only $369 brand new and with new warranties.
I used to work for Rumbelows 1974 Service engineer down to component level .. left the trade in 2003. Thanks for posting .. There's not many engineer's now, they're just fitters ..
Brilliant diagnosis, explanation & repair. I’ve never watched any of your videos without learning something new. Thank you for sharing your lifetime of experience here! 🙏
Skimping on a resistor wattage that basically has no value. Thank you for the insight and circuit analysis. This is how we learn - by sharing knowledge.
Well done that man, all understood. Inbuilt obsolescence, underated resistor and after 5 years it's time to buy another TV. Great video and thanks for the share 👍
@@michaeldranfield7140 Exactly. I would expect that the designers have the necessary knowledge to make the right choices for components. Then there's the CAD software they likely use; that can make the calculations too. I have heard about electrolytic capacitors in flatscreen TVs being deliberately underrated in terms of operating temperature. 85°C fitted where 105°C is needed for a decent service life. When failure occurs after 4-5 years, the TV is thrown away. More turnover for the manufacturer, more waste for the planet. To do things right would cost €1 or less per set, at mass production prices.
Thanks Mike, very informative. I had the same kind of issue on a different set, the PFC circuit. When heating up the board with a hair dryer then the pfc circuit started working. I turns out that the little electrolytic cap that smooths out the vcc supply to the pfc ic was high esr. That took me 5 hours to discover
@michaeldranfield7140 Can you perhaps advise me on a panel issue? I have a Samsung UA55NU7300K with a failed panel. You posted a video on this but there is a difference I wanted to discuss with you.
Well explained and repaired. When you have a spare moment (ho, ho), as other have suggested, it may be worth measuring the drop across the 10R resistor to determine what current is flowing and how under-rated the previous resistor was.
From the initial diagnosis there was 15.1V on the transistors emitter, if the PFC chip is expecting 12V the three volt difference equates to 0.9W which seems strange especially as the 15.1V was not a fully unloaded reading so probably close to the correct voltage considering the transistor was also dissipating around 2.4V with the 3V difference from it's collector. Maybe the PFC chip runs higher than 12V nominally but requires it's initial start current to not pull it any lower than 12V (cap charging etc). That could explain the resistor's reason for being there.
@@alasdair4161 Indeed, hence the suggestion for a little more diagnosis if another set comes in. We can determine that 900mW was being dissipated (in whatever state the PFC was in) and that is clearly way too high for the original and replacement SM resistors. I suspect (I hope) that when the PFC is running that there is very little drop across the resistor. The issue may be that the designers did not account for a pre-start or PFC failure situation (no design can accommodate every potential component issue) As an aside this in no way diminishes the work that Michael performs (which way exceeds my skills).
@@AeroGraphica They can fail that way. I've even had zeners adopt a strange thermal drift characteristic that makes the fault really interesting to diagnose.
Thanks Michael for your you tube fault guide, I have a Samsung with the same clicking noise and replaced the SMD with a 10ohm Metal 1/4 watt resistor and the set works just fine, thanks ever so much for your help, parts cost 85 Australian cents.
Great video Michael. I noticed the 10ohm res had a zero ohm link in series. Maybe originally they specced two 4.7ohms resistors in series but the bean counters won!
i had a similar one few years ago and i tryed hours of hours of toubleshooting and change components,but i was not able to fix it! i was so mad about it, that i dont want to buy a replacement PSU! it was 75$, so not that big, but my frustration was so high, that i refuse to work any longer on this tv! very good job
Its not easy trying to find a fault without a schematic diagram but cheaper than a new board , especially when you have the same fault more than once .
@michaeldranfield7140 I used to perform component-level repairs on electronic equipment during the 1970s, and it's wonderful to see that there are still a few people capable of doing this today. Excellent video, thank you for sharing!
a good understanding of how these systems operate is useful but the problem with new sets is there are no schematic diagrams so most of the time its more good luck than knowing what your doing, the official thing to do is just replace the whole board but usually this cost more that most sets are worth .
@@michaeldranfield7140 Yes, you are right. Back in those days, detailed schematic diagrams were available for almost all TV models. This meant you didn't have to rely on reverse engineering or guesswork; instead, you could scientifically troubleshoot and fix the issue. Thanks
@@michaeldranfield7140 sorry for my poor English, but the way you identify and clarify , resolve and teach present is clear and not forgettable. God bless you. Josey
I remember these CDs and web sites with repair instructions. "Sony TV chassis xxx turning on slowly with green line at top of screen, remove screw of lip holing PCB at the front, break way plastic lip, re-solder the voltage regulator". That's literally how I remember that. And indeed that fixed it, turned a 3 hour search into a 10 minute repair.
I'm sure everyone could do this if there was a service manual available , most manufactures only supply new boards so they no longer publish any schematic diagrams , you have to rely on datasheets from the chip manufactures to give some clue to how something works , its all well and good but very time consuming .
Good vid Micheal! Why on earth didn’t they fit the higher rated resistor in the first place - SMD resistors aren’t exactly expensive and the difference between the 2 sizes must be tenths of a penny…
I've worked in industry so I can tell you the possibilities: 1. one million TVs manufactured and a saving of one tenth of a penny per set adds up to 100,000 pennies or £1000 pounds. It's not a huge amount but if you can do that with several components it adds up. 2. A TV only has to last the warranty period so, if you make it fail after the warranty expires, that's a new TV sale. 3. the specified component was out of stock so someone used the next nearest "equivalent". 4. the original designer didn't bother to do the maths or made a mistake. 5. the resistor was from a bad batch. 6. glue or other contaminant caused the resistor to corrode (not in this case but a common problem).
Given that these was space on the pcb to fit a bigger one this could have been a deliberate act to make sure the set didn't last too long but someone has also given a whole list of reasons it could be.
@@manolisgledsodakis873 - although I do agree with all of your possible explanations, there is one that might make more sense: the zener diode at the base of the pass transistor is no longer operating properly, and is at a voltage higher than it’s original nominal rating. Thus the voltage at the emitter of the pass transistor is too high, pushing more current flow to the load. A measurement of that zener voltage compared to its nominal voltage should answer whether this is the case or not. If not, then maybe that 10 ohm resistor was improperly specified in the design.
9:38 that was clever I never thought of that using the iPhone as a microscope I was already contemplating on buying a dedicated one, thanks for that wonderful idea 👍
@@michaeldranfield7140 Because of your Brilliant Idea, I will just have to purchase a “phone holder arm” that I can just clamp the iPhone into saves me more money for not buying the electronic microscope, it’s a win Mate 👍🏻 thanks again for sharing your brilliant ideas
Btw you've got yourself a new sub! 😊 Great diagnosis and explanation and good to see another fellow tech/electronics enthusiast here in the UK! 😊 You sound as though you're from Leicester or further north, Yorkshire perhaps? I'm down south in Surrey 😊
To save money and get away with it, oh and then sell us a new tv .I stopped repairs on tvs in 2004..on wide-screen sets.. I've done a few over the years but don't have the time anymore.
@@waynewayne3709 technically speaking repairing TV s should be very easy now , just fit a brand new board and away you go , the problem is boards are so expensive no one wants to pay , so where ever possible I always look for the fault first , new board is last resort.
Samsung uses underrated capacitors in their power supplies. I have see this problem in 19 inch PC monitors to big TV sets. Since back in 2005 when I purchased my first 19 inch flat pc monitor.
Don't get too excited, there is no service manuals for most sets now so a lot of fault finding is just down to good luck , unless you just replace the whole board like the manufactures want you to do .
I have a 55 inch Samsung UN55RU8000FXZA and it has a similar failure. 1) The standby light flashes momentarily when I try to turn on the TV but there is no picture/ sound/ or backlight. 2) The 3 electrolytic caps on The Power Supply Board at the top left ( near the o/p to the main Board) have 'domed' tops. 3) When I unplug the Main Board from the Power Supply Board the Backlight turns on. 4) The Main Board does make a sound at turn on like a 'Flyback Transformer' (but only for a moment). My first thought was that the Main Board has a short that is drawing down the Power Supply & keeping the Backlight from turning on. But the other possibility is that the Power Supply Board can't source the current to the Main Board. 5) Additionally, I disconnected the 3 output cables from the Main Board & the backlight is still not lit. Have you any suggestions?
I did one of these recently with a faulty opto- coupler. Im guessing when you soldered those wires onto the resistor , it partially rectified a defect inside the resistor hence the 30 ohm reading ..iv seen heat from desoldering components temporarily "fix" internal open circuits in components before , must be the thermal expansion of the metal inside causing breaks to become bridged back together
Hi, can I ask if it was the same PSU as here that you found the faulty optocoupler? I currently have one of these PSUs I'm trying to repair and have no V on rails or backlights. The resister that's the culprit here reads ok and I have 15-17V from the Aux winding on the SB transformer so was beginning to suspect the optocoupler? 🤔
@@5pr1nk57 it was very similar to this psu. Ive done 2 the same board recently , one had a dry joint and one had a bad opto-coupler, it was reading about 300 ohm on one side of it with the probes either way round which is why i suspected it , the other optocouplers all gave similar readings in ohm mode and diode mode . Id just change them all and then you can rule it out .
@@5pr1nk57 after looking at this video again im sure its the same psu. I first thought the fault was the 7 pin chip on the primary because it was getting warm but nothing else was and there was no output on the secondary . Its a pwm/mosfet ic, i bought one from italy and changed it and it did the same thing which is why i started looking at the surrounding standby circuitry and optocouplers etc
@@reacey I've actually since found the fault! There was a small 2A ceremic fuse hidden under some gunk that was open and it revealed a short on the latter part of the primary side which was 2 Smd Mosfets on the reverse of the board so just have to pick some up now as no stock/donors here :)
you wont get one of these now unless you are very lucky , it was made by Phillips back in the 1990s to aid repair of the new Phillips G90/ G110 sets that had just started using surface mounted components , there is also a transistor and diode box which I also have .
Samsung makes to easy to Diagnose their TVs,If you disconnect Main board and it Turns on its your Main board Replace or fix if you know how if it still doesn't turn on its your Power board .Theyre the only ones that do this in the industry Cheers :)
That's the only good thing about Samsung but you still don't want to jump to conclusions, in this set with the main board disconnected the backlights were flickering which might lead you to think the backlights were faulty when infact it was the PFC not running .
Interesting stuff, thank you. I’m currently trying to diagnose a Samsung N87 from 2007. Replaced the caps (well the starter round black ones), no joy. Checked standby voltage and it’s clicking 1.8 to 13v.. standby should be 5.3
A classic example of fitting underated components that sooner or later will fail. We were trained to fault find to component level, today it is just to board level which is very wasteful. What will happen when our generation has gone?
Like you I was trained to component level. If we had even suggested the possibility of replacing an entire board the service manager would have fired us on the spot! These days as you say it's all about being a board jockey. Even I have had to resort to doing that, in a situation where an electrolytic capacitor had leaked onto the PCB causing the high voltage present on that cap to track over the board then start arcing then burned a large hole in the board. It was beyond repair as it was a multi-layer board, so I contacted the company and the solution - "replace the entire board". They sent me a complete replacement. I don't know what the future of electronics will be when we are gone. Very likely there won't be any servicing, people will just toss their broken appliances and buy a new one because they will be so cheap - much like how it is now, except we still have people repairing some things today.
@@sw6188 This is the way the world of electronics has gone, and consumer electronics has been steadily turning into a throw away situation since the 80's. I can remember asking for a service manual for a Philips radio cassette to be told that there wasn't one or any parts stocked to repair it, if they failed under warranty they just replaced it. One option is to make the items self repairing, once the last of the good circuits have blown , then it item is scrapped. I first came across this technology working on the Euro Fighter, they had three backup circuits for the critical controls when i pilot reported a fault we just ran some diagnostics and replaced the faulty module, but not the faulty component. This is all paving the way for everything going AI, then no one will be needed!
Great video and troubleshooting masterpiece, Michael. Thank you for sharing. Can I ask , how much time does it usually take for you to get into the right place like for example in this case?
The first time you do it it can be hours, or sometimes I look and cant find the problem and put it to one side and comeback another day , all this could be avoided if there was a service manual with schematic diagrams like there use to be years ago, now you have to look for datasheets on the internet for specific chips to set an idea of how a chip operates.
Sometimes ,especially on some older samsung or lg sets,just resoldering the st by and main chopper transformers solves this issue.Cold solder joints can be the issue of relay clicking and no power on.
Dry joints seem to be much more common on equipment using leaded solder than it is now but yes I have had loads of Samsung in the past with dry joints on heats inked components.
For those wondering why a "100" marking is 10 Ohms. ABC -> AB . 10^C (so C is the number of 0 you have to add to the first 2 digits) 100 -> 10 . 10^0 = 10 . 1 = 10 102 -> 10 . 10^2 = 10 . 100 = 1000 = 1k 476 -> 10 . 10^6 = 47 . 1000000 = 47000000 = 47M
Hi brilliant video, really interesting and informative, what does it mean when a TV powers up but has a dark blue screen? I've 2 tvs like this and want to repair then as they are both smart tvs. Thank you in advance
if the sets you refer to with the dark blue screen are made by vestel then its the LCD panel that's faulty , take a look at the video I posted just before this one , the Hitachi with no picture as there is a work around to make set the set to produce a picture.
hmm if 12 v at the pfc chip, and output of the transistor is 15v, that means 3v across that resistor, meaning 0.3amp through it, 0.9w dissipation , ?! no wonder it fried! did you measure the actual working voltages at the pfc chip?
I didn't measure the voltage at the chip which was a mistake but some chips have an internal zener diode on the Vcc so this may account for current draw .
Who knows how many TVs were thrown out just because of this faulty little resistor. I also noticed that the voltage over the 450V caps was very fluctating, is that normal ?
I'm a year older than you and remember reading Everyday Electronics and ETI as a great read! I have a Samsung UE32T4307AK (so a single pcb, newer gen.). I was interested if you had had one to look over yet? This one doesn't power up, but the front telltale LED is on for about 5 seconds, goes off fleetingly, then straight back on, over and over. The PFC route sounds interesting! There is 331v across the main cap. There isn't an S3050 PFC chip that I can see, but there is a 4801A chip, which does have 13v going to it. There are loads of similar, working spare boards on eBay. I think there is a lot of demand! Maybe the panels die early and these TVs get broken for spares? A briefly-borrowed pcb from an identical neighbour's TV fixes it completely. Do you know if this is a 'standard' problem, hopefully with a 'standard' easy, fix! TIA Great videos, BTW!
So glad I found this! I picked up a dead Samsung 55" UE55F6500SB to repair and stick in the bedroom. It has has the clicking relay and 2 blinks of LED with no startup fault. Interestingly the backlights don't work when the mainboard is disconnected but there is no voltage at the LED output not at mainboard output apart from SB 5V & PWR On 3.2V. I've been testing and researching all day and am stumped! Can find little about this set or faults online. Your set here uses the same PSU board and I just checked that resistor but it reads 10.7 ohm so seems ok? 🤔 I am suspicious of the PFC section though as there's no voltage on rails other than SB, no voltage across the 400V smoothing caps and the PSU seems in a safety shut off/boot loop. The last point you made about a short in the SB transformer is interesting though, I do have 5.3V in those diodes above but not the aux tap off and everything else dead in the secondary? Any other thoughts?
I would take a close look at the SB transformer if the 5.3 volt is present but no other rails , check the primary resistance , in the set I had although the 5.3 volt was present I don't think it was possible to draw a heavy current , however you should still have charge on the reservoir capacitor in between clicks , I think I would be tempted to short over the repay contacts with a 60 watt bulb so you can keep power on to aid fault finding . I think in the set I had the primary winding of the SB transformer had an unusually high resistance primary and when I un wound it you could see where there had been a flashover and the primary wire was broken but the transformer still worked to a fashion as there was a conductive path caused by carbonisation .
A simple switching pathway became complicated... I'd use a simple method to do that with the opto coupler and 2 tiny MOSFETs without zener diode without resistor .
I have the clicking on my samsung, the on/off light flashes 2x 5 times with a longer pause. I'm gonna follow this troubleshooting and see if I have the same issue.
This video is ALL the information i need for a 60 inch Samsung... but the video is blurry.. you didn't show where these components were on the other side of the board, and where that lil resistor was even located, in what area..
Hi Michael, do you think the resistor was sized for a fusible link? more than likely it was selected to shorten the life of the TV ( engineered obsolesce) Rich
Could well be built in obsolescence and deliberately designed to fail , not easy to find the first time I had this fault as there is no schematics for most sets now .
Yes there is a capacitor selection box also, I very much doubt you will buy one of these now though, these were produced by Phillips for repairing the G90 and G110 sets of the 1990s.
@@michaeldranfield7140 That's a shame, ah well, thanks anyway Michael. Really interesting to see component level repair like this, and good that the set was saved from a premature end👍
Hi, Excellent video. I have Exactly the same behaviour on my Samsung TV UA55D6400UJ but when I disconnect its Main board from the Power supply board it stops clicking... So I assume The problem could be at the Motherboard?
While motherboard connected i was getting around constant 385v at reservour caps but after a while relay goes off and back on again and again like every 15 secs or so
Michael, i have this problem with my 40 inch Samsung tv: I power her and after 5 min, she is dead! I have to take off the socket and then to wait 3-4 minutes begore i plug her again: She is ok for 4 - 5 min and then again dead!! I do this procedure 4 -5 times and at the End she is ok!!! But if i close her and open again in two hours, it happens the same!! And i have to do the same procedure once more! Any ideas;🙄 model:LE40B651T3W,made in Slovakia Thanks,
Sounds like it may be a dried out electrolytic, you can check for this by warming up the caps with a hairdryer but also check the PFC voltage is not too low
I have a question about this pfc .SInce a rectified voltage is Ac X Sqr2, in our case its 230 X 1.414= 324 V dc.What boosts further the dc voltage to almost 400V DC ?
Thanks Michael for your videos. I have two Samsung 70 " tvs same model. Both have the same fault, main board. I usually buy parts for what I need, but unfortunately I couldn't find the matching one. My question is, are you able to fix these boards? If so is there a better way for communication? Thanks
there is no schematic diagrams for most LCD sets now so most fault finding is just a matter of luck , ideally you will need a working board to take comparisons from .
@@michaeldranfield7140 That's really useful. I bought an expensive scope but it's still sat in the box. As a hobbyist I just need to have a better view occasionally and just can't face setting it up 😁
