Mulja tv repair portal
Equipment Repairs => LCD TV forum => Topic started by: Contrast John on March 11, 2010,14:15:59
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Hi All
Had one of these sets in for repair stuck in standby and resisting all attempts to start it up. Found (more by good luck then judgement) that if I disconnected the ribbon cable from the main board, that the set would start ok. Tried the cable in and out a few times to prove it wasn`t just a coincidence and then while the cable was out started the set, went into service mode (menu 4725) and performed INIT NVM. Reconnected the cable and found I`d cured the problem. Clearly a case of data corruption, presumably in this instance between the main and dvb panel. Don`t suppose it`ll work every time one of these sets is stuck in standby but definately worth a try. Anyone else come across this?
Have attached manual for 17mb29 but note that that the standby switching voltage (pin1 of PL807) was found to be 1.5v in standby and 0v when working.
Regards
John.
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John, I have joined here today just to say your a star.. and above fix worked perfect..
Thank you very much :1st:
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John,
Im having probs again :( all I did last time was remove ribbon cable and put it back and it worked a treat,,
Im no repair man so i tried pressing menu 4725 but nothing happens any chance you can talk me through it to preform INIT NVM as you say??
Thanks
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Hi kingkebab100
Dissapointed to hear that you`re still having trouble.
Sounds like your eeprom IC is faulty and has lost its settings again, probably along with a few more. Without the set running its not possible to perform a reset. Replacing or reprogramming the eeprom IC is the only answer (apart from a new signals board).
Duff eeproms are the scourge of modern tv sets and with not much available in terms of spares or technical support many sets are forced onto the scrapheap for want of an IC that would make for a simple and economic repair.
Sorry to be the bearer of bad news and if anyone knows a scource of spares for these models I`d be interested to know.
Regards
John.
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Thanks for your reply John,
I can get set running by taking ribbon on/off board a couple of times and the remote will turn on..
TV will then work on/off for time span of last power up of 2-3hrs.
But leave powered off for any longer and it will not switch back on :(
I just cant seem to get into service mode and preform
INIT NVM ....
if i am able to get into service mode how do i preform above task(s)
Thanks again !
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Hi again
To acess the service mode;
While the set is working press the menu button on the remote control. The normal menu should appear on the screen. While it is displayed press the number keys on the remote control in the order 4 7 2 5. A new menu should appear on the screen. INIT NVM should be at the bottom of the new menu list. Scroll down to it using the scroll keys then scroll right to set it. If you cant get the service mode to appear, or if you still have problems after a reset, you will need a replacement eeprom but as I say spares seem non existant for these models.
Best of luck
John.
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Hi John,
managed to get tv to turn on after about 20mins of taking ribbon on/off lol...
even managed to enter service mode and put INIT NVM to yes...
when i switch it off and check service mode again INIT NVM is back on no is this the norm?
just off out now for an hour and leaving it switched on... then ile power down for a couple of hours ...
I will report back and let you know if it turns back on after power down heh heh...
Thanks for everything :brinda:
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John,
Its buggard lol left it switched off overnite and now no response 'again'
Thanks for help
Ebay it will be going now :blush:
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Hi Again
Well you did everything right, but it just wasn`t to be. Hope it earns you a few quid towards a new set.
Regards
John.
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Hallo guys. I am just receive the 3 that same TV`s. I tryed this as well. I don`t know yet if this help but is unbelievable. All 3 TV`s have the same problem. stuck in stand-by. did this help you .cheers
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John,
Just curious does the TV you repaired still work with that fix??
Rgds
KK100
Romanko... Ive tried 2/3 times now to repair this Model with John's help but I'm afraid its a very short lived fix but worth a shot on your Tv never the less... Good Luck
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Guys. I did put TV`s into the service mode and preform but after this fix and remove it from the socket till this morning,the same problem again in all 3 TV`s.I just can`t understand how TV`s svitched on sometime. When I plug it into the el. and do nothing for a while, TV`s start perfect but not allthetime. If I plug it in and I strait push the channell button coming on after several try.Dont you think, power supply may be bad ? I `v been looking for sam bad capacitor but all look`s good. Any different idea how to fix this crap? Romanko
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Romanko, Im afraid as John says below.. the TV is for the scrapheap..I will be putting mine on ebay tomorrow and will let you know how much it fetches!
best of luck !
Hi kingkebab100
Dissapointed to hear that you`re still having trouble.
Sounds like your eeprom IC is faulty and has lost its settings again, probably along with a few more. Without the set running its not possible to perform a reset. Replacing or reprogramming the eeprom IC is the only answer (apart from a new signals board).
Duff eeproms are the scourge of modern tv sets and with not much available in terms of spares or technical support many sets are forced onto the scrapheap for want of an IC that would make for a simple and economic repair. Sorry to be the bearer of bad news and if anyone knows a scource of spares for these models I`d be interested to know.
Regards
John.
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Hi Guys
Customer hasn`t reported any problems so far. Beginning to think I just got lucky with this repair! Will post an update if theres any news.
Regards
John.
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Hi .maybe You right.do You know, which eeprom is this? at this motherboard are two. U690 an top left between power ribbon and HDMI conn. and U698 beside tuner and audio buffer TEA. I am just start two tv`s and they work again .(nightmare) I think we will find out what is this about. Romanko
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Guys, You wont beleive this but.....
I brought the TV to work today to take photo and put on Ebay and tried it again....
.... and the darn thing is working perfect WTF :dubbio:
So I've powered down and will re-try again later..... LOL
Nice 1 for no come backs John
Fingers crossed Romanko nightmare indeed :wacko:
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Hi. so I`ve sleep well. I am just turned on TV ,was pluged in from last night and is gone mad. when I want change volume down I have now source select there. definitely gone. I will keep them for parts. :mad:
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Hi Again
Just got another one of these sets in for repair with a similar (but not quite the same) problem. Thought it might be worth comparing with your specimens. Set was stuck in standby and no amount of cable removal would persuade it to start. Found that if I heated the area around IC U696 (MP1583) with a hairdrier the set would operate normally. U696 is located on the top right hand edge of the signals board. Turn off and leave for ten minutes and it was back to the standby problem. Got the impression that this 8 legged step down regulator chip might be faulty. Interestingly it supplies the 3.3 Volt rail for the eeprom which could explain possible eeprom corruption or damage. Never quite sure using a hairdrier though as the heat seems to spread out a bit so guess replacing the IC would be a starting point. Don`t know if I`ll get to try though as the owner is considering his options!
Hope the info might be usefull.
Regards
John.
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Hi.hopefully you right. I`ll try and let you know. romanko
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Hi again. I`ve been try heat it up and you are right. coming on allthetime. I have two MP`s 1593 DN so ,do you think,can I replace them for thisones ? datasheet says just higher voltage. romanko
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Hi romanko
The IC is actually shown as a MP1593 on the schematic, but not sure if the associated components would be the same values for a MP1593. Not easy to tell without markings on the components or the board. Probably worth a try if you`re good at soldering, but keep in mind that you may need to fit the right IC to avoid confusion over whether or not you can use a `93.
Regards
John.
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No joy again here fellas... so picture being taken as I type... off to ebay it goes...
Gl with your sets..
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Hi again. I`ve been replace the MP1583 from good working board and same problem,so this is not solution. too many problems with cheap tv`s. I`ll lieve one for labouring and give away next two for parts.Have one more Nordmende NM32780 from friend with same problem. If anybody will find out what may be a solution please reply back. good luck- regards - romanko
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hi all
dont supose anyone has found a solution to this fault yet?
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Hi Guys
Was given one of these sets recently with the problem where U696 needs a dose of the hairdryer to start it and spent a little time scoping waveforms. Ended up with the 'assumption' that U696 couldn't deliver enough current at 'power up from standby' to get the set started. Got round the problem by adding a 1000 microfarad low impedance type electrolytic capacitor from the output of L 107 to chassis. ie across the standby 3.3 volt line. Found then that the set started every time. Don't know if this would always work for this problem, or if there is a better solution. Anyone have any further info?
Regards
John.
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hi john
I went down a similar path, changing c141 470uf for a 1000uf, seemed to have had positive results but only ever seen one and the customer was at the stage where if it acted its self again it was going in the bin, so guess we will never know.
did find someone on ebay who new the secret of this repair and was offering a pcb repair service for about £50 I think, I contacted him and offered him some shiny coins for his secrets but he refused point blank (Meany, hope the Yule tide log slips from his fire and burns his house down)
, but you never know he mite have an Ebenezer moment over xmas and share his secret.
if not lets hope these sets soon pass into history
daz
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Hi daz
Think we may have discovered his secret! Will keep you posted if any more show up.
Regards
John.
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Interesting discussion going on here! I have a Prosonic tv with the same mainboard and stuck in standby too.
I'm going to play with some ribbon cables now, could you highlight me which one I need to unplug?
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Hi
On the first set disconnecting the large white ribbon cable between the main board and dvb board got it started. On the others heating U696 on the mainboard with a hairdrier got the set going. If this is the case try adding the capacitor as suggested. Interested to know the results.
Regards
John.
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The ribbon cable doesn't do anything (the very thin one).
The power led is on, but the screen stays blank (off).
I pressed some random buttons (tv/av, menu, pg+, pg-, vol+, vol-) and some kind of test program started running... flashing the screen on and off and displaying gradients.
At least this means the panel still works.
...If only I had a hairdrier!
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Just to be sure, I quickly made the attached image to check for the possible repair options for adding/replacing a capacitor.
Could someone quickly check if I am looking at the right components and connections?
Option #1 replaces the current 470uF capacitor for a 1000uF, I think I'm looking at the correct part (C141)
Option #2 adds a 1000uF capacitor, but I'm not sure I'm connecting this in the right way... Is that cube part L107 and is the output on the right?
Thank you!
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Hi Again
Option #2 is the one I used. Exactly as in your picture. Soldered the positive of the capacitor to the right hand tag of L107 (output) and attached the negative leg of the capacitor to the earth screw.
Good Luck
John.
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An update again from my side; I tried adding and changing capacitors, but no luck...
I found this thread: http://www.tv.quuq.org/forum/index.php?topic=3433.0
It is somewhat the same topic as in here, but the problem has been found in the psu.
I will try adding a 1k resistor between pin 1 of IC301 and ground tomorrow.
While fiddling with capacitors I did some measurements and found that when the set is plugged in and the power button is on, the standby pin puts out around 1,6V. The documentation says standby is ON between 2 and 5 volts and off when 0. Would it be an option to ground this pin so it stays 0?
Another thing is that my unit seems to be stuck in some kind of test mode; when I plug it in, wait for it to power on (blue led comes on) and press the program+ or program- button, it shuts off the blue led, but after 10 seconds or so it starts up the display, flashing the screen slowly and showing black to white gradients...
Finally I found the ebay seller who offers replacement sets, I emailed him, but he want to have my defect board. Clearly he knows how to overcome the problem, but won't share it.
While looking at his pictures though, I noticed a different capacitor on his boards; he seems to have changed c536, maybe someone else knows if this could be an option that makes sense.
Thanks!
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Hi mrfriss
The 1k resistor mod is a possible cure for a lazy ccfl backlight tube. If this was your problem you would have the symptom of sound ok but no backlight illumination. Switching the set in and out of standby would not be an issue.
Seem to recall that the documentation about the standby switching voltage was incorrect in some way but can't remember the exact details.
Think your set is exhibiting a fault different to mine because it appears that you are able to bring it out of standby. From the description it sounds like a corrupted eeprom IC stuck in some sort of test mode. Try holding the menu button on the remote control for a few seconds while the screen is flashing. Sometimes it can act as a reset.
Checked on the circuit for c536. Assuming the numbers are the same on this version c536 also decouples the standby 3.3 volt line - just a bit further downstream. So upgrading it would have the same effect as either of the capacitor mods you have tried.
Regards
John.
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Unfortunately no luck with the menu button on the remote or set itself...
But you are right, I CAN get out of standby mode, either with the buttons on the set itself or remote control. Only thing is that it goes into some kind of testing mode.
I'm going to look into the eeprom, maybe there is an alternative way to get it out of reset or something.
If anyone has any thoughts, please let me know!
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Another thought... could someone guide me through the menu structure to reset the chip?
I believe my set is fully working, but stuck in a test display sequence.
So after pressing 'menu', '4', '7', '2', '5', how many ups, downs, left rights do I need to do a "INIT NVM"?
What other options do I have in this service menu?
Thanks!
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Hi mrfriss
From memory- MENU 4725 should bring up the service display. Scroll down to RESET option. Press right scroll button. You should see another screen that tells you to press the green button. Press green and it should reset the software before switching itself to standby.
Best of Luck
John.
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Thank you, but not exactly what I meant...
I need exact button presses to reset the device (or do something else that could get my device out of display test mode).
So if anyone has a device with this main board, please enter the service menu and post the options or take a picture and share it, somewhat like this (including sub menu's): http://www.djsmiley.com/got/pics/techwoodtv/hires/dscf9824.jpg
Frustrating that the set fully works, except displaying the images (sound works and it responds to button presses)
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HI again guys. I didn`t have enough time to have look back on these sets but fault is definitely on the PSU board,that`s my opinion. Like I set before, I tried change couple working chips but without change.Few months ago I change all those Big caps,for value at least half more like they was.One of these sets is working over good few months with no problem at all and customer is fully satisf. Guys, do not put tv into the INIT NVM reset mode .That is only wasting the time.I did this on other two sets before and then I has to reprogram all settings in Service mode.Every f...... step.reset of all factory settings so this is a bad idea for me.My Set is coming on after about 10 seconds when blue light is off,self test or something like that,no idea but then working perfectly. I`ll have the same unit for repair on table this saturday.Caps should have a Value of around 1200 uF per 1 Amp floating current DC.These G-Luxon,Teapo and similar family of 85 °C chineese piece of shity caps are not suitable for switching power supply. Use real low ESR 105°C selected brands of caps and also check the datasheet.Main board rechecked for bad caps and dry joints by ESR and other eguipment.1000uF replaced by 1500 and other with higher value. Do not exceed too much,double value my cause some fault.Try this ,works for me :34:.Good luck.