Question about IBM ThinkVision L170 17" LCD Monitor

5 Answers

Suspect backlight inverter circuit--desktop appears completely for 1s and then loses backlight

Desktop appears completely for 1s and then loses backlight. Pushing the analog/DVI select button brings backlighting back on for 1 second and then drops. i suspect the inverter circuit as i found one 10v1000µf cap (C551) blown. I replaced this and its counter-part a 25v470µf cap (c661) with 25v1000µf and 25v470µf caps, respectively. Same symptoms. I am uncertain where to go from here as it would appear the backlight lamps are functioning and the inverter appears to work perfectly for about 1 second and then drops power to the lamps. I do not have a B.O.M. or schematic, so I am really troubleshooting blind. I suspect a protection feature is of some sort, but again, i have no schematic to reference. Where do i go from here?

Posted by on

  • 4 more comments 
  • Noel Rusnell
    Noel Rusnell Oct 16, 2008

    To clarify, the first step in troubleshooting was to look for physical damage and re-seat cables, checking components one by one for visible signs of damage. I am unsure as to where to go from here. I do not typically perform shotgun parts replacement, but i do check each out of circuit. The lamps check out ok and all light up for one second. I am not understanding the cause of the inverter to be fully-functional for one second and then shut down. I am suspecting an over-voltage protection circuit or something of that nature--beyond the obviously failed and replaced 1000µf cap (C551) i am not sure where to go.for this symptom. Part of the problem is i do not have a schematic nor B.O.M. to reference.

  • Noel Rusnell
    Noel Rusnell Oct 17, 2008

    B+ is 14.44V, regulated 3.3v, 5v and 12v is present on the video processing board and 5v, 12v are both present on the power supply/inverter board. I am in dire need of a schematic to be certain, but i am leaning toward a faulty BIT3105 CCFL Controller as it has built-in dimming and over/under-voltage protection circuits as well as open lamp detection...a little more testing is necessary...a schematic with correct pinout values and B.O.M. would be really helpful here as i could better decipher the current path and TTL signal/switching processes. I am uploading images showing the power and inverter board along with the blown 10V1000µf cap and of the 1-second desktop--you can well imagine the fun i had timing the digital camera to capture the display ignition
    .
    here is the link to the datasheet for the BIT3105 Controller: http://pdf1.alldatasheet.com/datasheet-p...

    Pinouts are as follows:
    ϑ 7.43V on AVDD and PVDD
    6.96V on CMP
    1.25V on RTDLY
    ϑ 7.4Von NOUT2, NOUT1, POUT1, and POUT2
    1.52V on EA
    213 Kω on PWMOUT
    1.3V on CTPWM
    .6V on DIMDC
    3.9V on SST
    0~.4mVon CLAMP
    ,

  • Noel Rusnell
    Noel Rusnell Oct 17, 2008

    the one cap appearing to have the bulge is one i was super-imposing with a pair of forceps for comparison. its replacement is shown immediately below it in place and is taller by a full height than its counterparts. the four 25v47µf caps and the 2 pots are connected to the BIT3105 CCFL controller (top-center of the board) which i described in my previous post and whose 7.4Von NOUT2, NOUT1, POUT1, and POUT2 drive the N&P MOSFET switches on the back side of the board. the 4 lamps check out good; however it appears i need an inverter transformer SPI 8TT00006 as there is an open winding at pin 1 and pin 8 on T4 (labeled faintly in blue on opposing ends of the faulty transformer)




    So, here's the kicker...SPI 8TT00006 does not come up for any vendors i can find with a google search or even eBay. Any ideas? know of spares on unused inverter/power supply board for these models? closest i could find is a long shot by Delta Electronics with stock number CIT011. your take?

  • Noel Rusnell
    Noel Rusnell Oct 19, 2008

    in the end--even those electronics suppliers who list the part as "available" on their websites, don't...and their techs and sales staff do not know what they are when contacted directly and have had to get their engineers working on locating a match. I've been waiting for a call back from the suppliers as to whether they can even do that...the customer has opted not to wait and picked up the old LCD...what for, i don't know...maybe all the troubleshooting was really what they were after all along. I suppose i could have or might have been able to use the unit for parts...shame they wouldn't at least wait for a response from the suppliers. back-up plan was to check e-Bay for a parts unit, but they refused to wait...

  • Noel Rusnell
    Noel Rusnell Nov 03, 2008

    thank you,

    kenny258...great suggestions--sadly, i no longer have the LCD to try these workarounds; however i am most certainly keeping this page bookmarked for future reference.



  • Ngewakl Soaladaob May 11, 2010

    I had the same problem but I had loose connection on my inverter board. I assume you have reseated your board?

×

5 Answers

  • Level 1:

    An expert who has achieved level 1.

    Mayor:

    An expert whose answer got voted for 2 times.

  • Contributor
  • 2 Answers

"Latched Open Lamp Protection Pin 4", disconnect the transistor 7002 "D" Pin on BIT3105 Pin 4.

Posted on Oct 30, 2008

  • kenny258 Nov 03, 2008

    Solution of Transform 8TT00006.
    1, I have been use an old Compaq laptop single CCFL transform to do the job.
    2, Or pull out 2 transforms and put in a bigger one for 2 CCFL, you can keep the good one for spare.
    8TT00006 primary only use 2wire that easy covert to other transformers, just let the CT pin
    open.
    ps; May be you need disable "open lamp protection" Pin 4 (lamp current unbalance).


×

  • Level 1:

    An expert who has achieved level 1.

    Mayor:

    An expert whose answer got voted for 2 times.

  • Contributor
  • 2 Answers

Hi,

I had just the same problem and suspected the BIT3105 IC, but this was working well. It was just in protection mode because of a broken hi-voltage transformer (one of the four). All the secondary outputs of this transformers have a resistance of 1 kOhm, but that one was open! By removing it from the circuitboard it was clear. On the bottom of the transformer was a black spot from a "spark-bridge". All the CCFL tubes were good. So it must be a production fault. The only thing you can do, is find a new or similar type of transformer and try to put it back. (maybe from an old TFT monitor)

I think this is also the problem by a lot of people here.

Best regards,

Jonathan

Posted on Feb 02, 2010

  • Level 1:

    An expert who has achieved level 1.

  • Contributor
  • 1 Answer

Hi i need the type number of ic u302 can you tell me the type numer of this ic ??? i have the same power supply but the ic u302 is burned up and now i cant read the type numeber..

send a mail to ladre5@hotmail.com

thanks

greatings

Posted on Sep 26, 2009

×

  • Level 1:

    An expert who has achieved level 1.

  • Contributor
  • 1 Answer

Hi I'm not very proficient with these technologies but I think the blockade is produced specifically SOP-8 mos additional power, Branding: A or P First line: 4600 Second line: BB03N15 or AD3S3L, which are responsible for the blockage of energy. ..

Posted on Sep 18, 2009

  • Level 2:

    An expert who has achieved level 2 by getting 100 points

    MVP:

    An expert that got 5 achievements.

    Novelist:

    An expert who has written 50 answers of more than 400 characters.

    Governor:

    An expert whose answer got voted for 20 times.

  • Expert
  • 159 Answers

Hi.
If you find one blow capacitor, you should change out all of them.
The large main one can usually be left go but for 6 bucks it is wiser to change that too while it is apart.
If that doesn't cure it then you have to move on to the transistors that run the backlight transformers.

A NOTE: you could have one failing bulb. Not sure if yours has 2 or 4, but it only takes one bad or weak bulb to give you the same effects.

bammbammfran

Posted on Oct 15, 2008

  • 2 more comments 
  • Fran Bednar
    Fran Bednar Oct 16, 2008

    Finding a schematic is worse than finding some of the parts
    forthese or any boards. They are secretly stashed with the creators.
    A
    bulb going on for a second is not long enough to tell if it is
    good(especially if it is still in the screen and you cant watch
    it'sreaction) easiest way to test them is with the use of another
    monitor.
    Being 17s are older units, this is a common failure in these.
    What are you showing for dc voltage at the connection to the video board ? Most older units run 5 and 12. Some just use 5vdc.
    Good
    looking caps are not always good caps. Standard cap meters don'talways
    give the most accurate info. An ESR meter is the best to use.But it's
    cheaper to change all the caps then to buy a meter and sincecaps are
    the most prone to fail with age, now is the time to changethem all out
    if your showing some dc which you should have since yousay you have a
    picture for a bit.
    If you have a picture, post it or email it to bammbamm@ptd.net


  • Fran Bednar
    Fran Bednar Oct 17, 2008

    DC values appear typical.

    The screen picture looks darker on top than on bottom..

    DID you individually check the bulbs ?

    Plugging them in ONE AT A TIME to get the flash on the screen may help
    tell especially if you disconnect the video to lcd ribbon (that will
    give you just a white screen and make their brightness a bit more
    noticable)

    Best way to test each is using another monitor as a power source- It only takes one to stop these boards in their tracks !!

    It almost looks like the one cap is bulged on the picture (could be the picture?)

    I don't see the transistors the the ccfl transformers, (Probably on the
    back of the board between the ccfl transformers and under the 4 caps )
    If it's not a bulb , I would think these are more likely the suspects
    than the actual ccfl control board. Check to see if any are grounding
    out against the positive DC side.

    Again. Schematic WOULD BE GREAT !! But !!?? I have to trace just about every board I work on since I can't find them either !!



  • Fran Bednar
    Fran Bednar Oct 17, 2008

    I thought that capacitor looked out of place !!

    There is always a kicker !!
    Now More FUN finding the part !! ??
    Only
    one inverter I've done uses one transformer to one ccfl and thatis a
    Benq, but those are square shaped. All my other boards use oneTrans for
    2 lights.
    That one is almost light a laptop transformer.

    You can maybe get lucky and get a cross reference from lcdparts.net ??
    LOT OF WORK for a 17" screen !!!
    It appears you are like me ! PERSISTENT !!
    Fran

    This may help finding a substitute
    http://www.cooperbussmann.com/pdf/dc8ad7...



  • Fran Bednar
    Fran Bednar Oct 19, 2008

    Hi.

    If you want an ebay parts unit, wait a while (YOU'LL SEE THIS ONE SHOW UP !!!!! )

    Can't please all the people all the time !! All you can do is try !!

    Thanks and have fun

    Fran



×

Add Your Answer

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

1 Answer

F-20 has sound but no picture, on VGA, or TV cables. Power looks ok. where can i find more info on testing for the problem and fixing. Thanks


Sound but no picture usually implies a faulty backlight. It may be simple case of replacing one or more electrolytic capacitors in the power supply or on the backlight inverter board. It may be that one or more inverter transformers has gone open circuit or short circuit, causing the inverter board to shut down. If this is the case then you can replace the inverter board with a universal inverter board but you will need to figure out the wiring. In most cases there are only three wires required - 12V, 0V and switching wire.

Feb 25, 2011 | Acer Ferrari F-20 20" LCD Monitor

1 Answer

Monitor trouble


More likely to have backlight inverter circuits failure, you need to open it up and look at caps, loose connections, burnt parts, check to see if you do have 12vdc feeding the inverter circuits. 15" monitor may not be worth fixing.
http://s807.photobucket.com/home/budm/allalbums
http://en.wikipedia.org/wiki/Capacitor_plague

Apr 08, 2010 | Northgate 15" LCD Tilt screen Innovations...

1 Answer

Planar Pe191m goes dark image seen with flashlight


I would suspect either the power suuply or inverter circuits, look for bad caps first which is common problem, see example of failed monitors due to bad caps: http://s807.photobucket.com/home/budm/allalbums
If you want replacement lamp, you can look here, it also gives you info on how to measure the lamps dimensions: http://www.lcdparts.net/

Mar 08, 2010 | Computer Monitors

1 Answer

Image on the screen appears only for 1 second; the green led remains ON. I suspect protection circuit of inverter bd. I can't find the related schematics.


I would look inside first for bad caps, then the inverter section, worst case will be bad lamps, see example of failed monitors due to bad caps: http://s807.photobucket.com/home/budm/allalbums
The inverter board will go into shut down mode if it detects current overload (bad inverter transformers, or transistors), open lamps circuit (lamp does not stay light up (conduct) after first firing of the lamp), lamps draw too much current.

Jan 31, 2010 | Computer Monitors

1 Answer

Picture goes black at random intervals


There are 4 c5707/5706 in the inverter transformer driving circuits, the cause of the problem was due to poor solder connection in the bias circuits of the transistors. Make sure to check that after you install the new transistors otherwise you will blowthem up. Common problem with this model. When the circuit drwas too much power from the power supply, it will shut itself off to ptotect itself.

Dec 16, 2009 | Dell E173FP 17" LCD Monitor

2 Answers

Screen goes black but still can see the desktop??


Yes this is a back-light problem. The fault could be the inverter board which supplies high voltage to the CCFL lamp or it could be a faulty CCFL lamp, this lamp is a mini fluro tube.
For service, parts and DIY info check out LCD Parts - click on this link to their WEB site : -
www.lcdparts.net

Oct 12, 2009 | HP w2207 Monitor

2 Answers

Screen is dim barely can see desktop in background


Usually this is a problem with the backlight, or inverter. Most of the time the inverter is the problem which is a pretty cheap fix. If its the backlight, then you will have to replace the lcd, which is much more expensive.

Normally this is caused by the power inverter for the lcd2.gif. It is a small circuit board right below the lcd, that powers the backlight. If you take off the front bezel of the laptop you should be able to see it, it will have a 2 wire power cord coming out the one end, and another plug in2.gif on the other end with several wires.

Check ebay for a replacment but make sure you get an identical model as the one you have, as they are very specific to each laptop. The inverter will have the part number written on it.

Sep 11, 2009 | Acer 22" X223w LCD Monitor

2 Answers

Samsung monitor picture clicks off after 2-5 seconds...


Yes, It sounds like the backlight inverter circuit is shutting down. No inverter power, no backlight. On some monitors the inverter circuit will shot circuit the power power supply which makes the power light flash on some it just kills the backlight. You can usually check with a flashlight. Hold the flashlight pointed at the screen and see if you can see any of the icons or background picture. If you can then it is the backlight circuit or backlight tubes, usually the circuit.

Buddy


Jul 24, 2009 | Samsung SyncMaster 204B (Silver, Black)...

3 Answers

Monitor goes on then off right away.


The backlight inverter is faulty.
THis means that there is either a loose contact or one of the transistors on the backlight inverter has blown

Jul 06, 2009 | HP Pavilion F1703 17" LCD Monitor

Not finding what you are looking for?
IBM ThinkVision L170 17" LCD Monitor Logo

8,844 people viewed this question

Ask a Question

Usually answered in minutes!

Top IBM Computer Monitors Experts

Donald DCruz
Donald DCruz

Level 3 Expert

17129 Answers

Brian Sullivan
Brian Sullivan

Level 3 Expert

27725 Answers

William Miller
William Miller

Level 3 Expert

8820 Answers

Are you an IBM Computer Monitor Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...