LG Flatron L1732TQ -Display "out of range"

[jarl]

I got this LCD monitor that seemed to be Ok, but: When you connect it to a PC via either the analog or the digital input, it shows an image as soon as I start the PC. After a few minutes the screen goes black and a message appears saying "analog out of range" (or digital, for that matter). A few seconds later the monitor goes to sleep, due to the lack of a "proper" signal.

Restarting the monitor doesn't help, but leaving it off for several (>15) minutes gives you a few seconds or extra video time. Google search don't help at all since most of the questions are from people running their monitors at wrong resolutions. In case anybody is wondering, I am 100% sure the signal I'm feeding the monitor is "within range"

I took this thing apart hoping to find one or more blown capacitors, but everything looks fine. The power supply (Lien Chang AIP-108 Rev 02) is built using Maxon GF capacitors, but none of them is bulging. Besides, can the power supply create this kind of problem, or is it safe to assume something else is fried (and the monitor is gone for good)?

The actual "brain" of the monitor uses different capacitors, but there isn't any obvious brand I can discern. There's something that looks like a logo (an "S") and a code like "CD112S" in the case of the 100uF electrolytics.

I'm hoping someone around here may have faced a similar problem before -and has been able to fix it-

Thanks!

[FIXITNOW]

Re: LG Flatron L1732TQ -Display "out of range"

17 inch monitor : 1280x1024
IS ITS MAX RES
What is the pc graphic set to ??

[magistertc]

Re: LG Flatron L1732TQ -Display "out of range"

Older LCD monitors were often limited to 60Hz refresh rate. Some newer ones will work up to 85Hz, but you might check (maybe with a different monitor) that you are set to 60.

[jarl]

Re: LG Flatron L1732TQ -Display "out of range"

Thank you for taking the time to reply.
No need to use capital letters here. I tried several different resolutions/refresh rates and the behavior is exactly the same (to quote myself: 'In case anybody is wondering, I am 100% sure the signal I'm feeding the monitor is "within range" ').

Trust me I won't be opening this thing if I weren't 100% sure the problem is the monitor itself

Now, to the original question... Can a power supply problem explain the behavior of the monitor? Any idea which brand are the main PCB's electrolytics?

[Bobdee]

Re: LG Flatron L1732TQ -Display "out of range"

Yes bad caps may be your problem
As to what brand caps, lucky dip
Time to open it, you will get good help from the forum members
Post pictures if possible

[stj]

Re: LG Flatron L1732TQ -Display "out of range"

a friend of mine has seen this a few times on something - it was a chip.
i'll try & fone him tomorrow to ask what monitor it was.

[PlainBill]

Re: LG Flatron L1732TQ -Display "out of range"

a friend of mine has seen this a few times on something - it was a chip.
i'll try & fone him tomorrow to ask what monitor it was.

Maybe the EEPROM???

Jarl, check to see if there is a reset sequence for the monitor.

PlainBill

[stj]

Re: LG Flatron L1732TQ -Display "out of range"

not the eeprom,
something semi analog.
it can be bodged sometimes by soldering a resistor across a couple of the pins.

maybe it's a pll or a reference oscillator.

[jarl]

Re: LG Flatron L1732TQ -Display "out of range"

Stj: that sounds great. I was hoping the problem would be a capacitor or something very simple, but it looks like its more complex than that. So, if your friend has seen this problem before it's great news.

PlainBill: EEPROM was one of my first guesses, but I have no way of testing that (that I'm aware of). In the service manual there's something about EDID, and something about accessing memory using a program (WinEDID). But what should I be looking for?

According to the schematics (It's a PDF... how can I make them available for you to see?) there seems to be two separate 24C02 (one for analog and one for digital), but since the problem happens no matter what input is being used I think the issue is probably in a component common to both. The scary part is that the only component I can find in that particular area has 100 pins There are also two 25P10VP and one 24C08WP close to the main IC

Now... regarding the 100 pin IC (U101): In the schematics that IC is indicated as "TSUM16AL", but the actual component says "Flatron F-Engine / FE2031-LF". Either way I can't find any datasheet about them, but inspecting around I found two spaces without SMC components (pictures). C110 looks like there has never been anything there, but C115 looks weird. I dunno...

[PlainBill]

Re: LG Flatron L1732TQ -Display "out of range"

The short story: The monitor stores user settings in a serial EEPROM. Things like brightness, menu language, preferred input. I guess the EDID might also be stored there, I don't know. Usually the data is stored with some sort of validation information - a checksum. On some monitors if the validation test fails you get nothing but a flashing power LED. On other monitors - who knows?

There are two fixes IF that is the problem. The brute force method is to replace the serial EEPROM. The simple method is to force a serial EEPROM reset. This involves holding down a combination of buttons and releasing them at a certain time in the power up sequence. A whole bunch of information on this can be found by Googling monitor reset. No guarantees at this price, and the symptoms aren't a close match, but it's an easy fix to try.

One note: Bad caps can be the cause of this problem.

PlainBill

[stj]

Re: LG Flatron L1732TQ -Display "out of range"

the problem sounds thermal - maybe freezer-spray time?

[PlainBill]

Re: LG Flatron L1732TQ -Display "out of range"

the problem sounds thermal - maybe freezer-spray time?

Always a good approach.

PlainBill

[jarl]

Re: LG Flatron L1732TQ -Display "out of range"

Reporting back...
I decided to buy an oscilloscope to check this monitor and a couple other things I have sitting around. And the weirdest thing happended when I tested this monitor.

I turned the monitor on, got the usual, normal image for a few minutes, and then the "out of range" message. The hottest running IC is U101, as expected (close to 50C, 122F). I cooled it with canned air, but nothing happened.

Then I probed the pins 96 and 97...
#96: when I touch it with the probe, it kills the display. OSC shows a constant 0.8V or so
#97: when I touched it, the normal image came back OSC shows a waveform similar to what should be there (I guess... still remembering how to use the scope). More importantly: when I removed the probe, the image was still there!!! If I touch it again, sometimes I get the "out of range" again, and by touching it again I can fixit -eventually-. It looks like pin #97 is broken???

Having identified this, how do I fix it? Right now the monitor is working, but I'm afraid after I'm done putting it back together it will fail again. What would you do?

Thanks!

[jarl]

Re: LG Flatron L1732TQ -Display "out of range"

(Sorry for posting again... I ran out of the 10 minutes I had to edit the previous message)
Got a better image of the two pins (last image)... how on earth could this have happened???

[philpem]

Re: LG Flatron L1732TQ -Display "out of range"

If you've swapped the caps already, I'd be suspicious of the two 22pf capacitors and the crystal. Crystals do wear out (the contacts basically break off the quartz slice), and when they're "on the way out" it gets harder to make them oscillate. Putting the capacitance of an oscilloscope probe on there might have been just enough to make it oscillate.

I'd try swapping the crystal, then if that doesn't do anything, swap the two 22pf capacitors.

As for those dimples in the pins... it looks like someone's used a scope probe to monitor the signal on them, and pushed down "just a bit" too hard. Thus the sharp tip has gouged the metal slightly.

Also check out that bit of "fluff" that seems to be stuck between pin 96 and 97.

[jarl]

Re: LG Flatron L1732TQ -Display "out of range"

"...it looks like someone's used a scope probe to monitor the signal on them, and pushed down "just a bit" too hard"

Hmmm... I wonder who may have been that someone But those leads must actually be made out of lead to get damaged like that... It looks really bad, and I don't think I was pressing that hard (I was using my non-dominant hand, though... so that may explain it)

I saw the "fluff" you mention, but it's too tight in there to be able to clean it adequately. Now... regarding the probe starting the crystal... wow. I didn't know that was even possible

I guess there's some SMT soldering in my future... We'll see...
Thanks!

[jarl]

Re: LG Flatron L1732TQ -Display "out of range"

Another self-reply.... I hate when this happens...
Anyway: I'm looking for the crystal at Digikey, but there are too many options and it doesn't look like any of those is what I need.
From the manual, what I need (X101) is a "6202TST001A / SX-1 SUNNY ,SMS, 14.31818MHZ", but I have no idea about the other options digikey is showing me (tolerance/operating mode/ etc). Would this one work: http://search.digikey.com/scripts/Dk...=478-4350-1-ND ? What happens if the "load capacitance" is different?

[PlainBill]

Re: LG Flatron L1732TQ -Display "out of range"

Another self-reply.... I hate when this happens...
Anyway: I'm looking for the crystal at Digikey, but there are too many options and it doesn't look like any of those is what I need.
From the manual, what I need (X101) is a "6202TST001A / SX-1 SUNNY ,SMS, 14.31818MHZ", but I have no idea about the other options digikey is showing me (tolerance/operating mode/ etc). Would this one work: http://search.digikey.com/scripts/Dk...=478-4350-1-ND ? What happens if the "load capacitance" is different?

Try this page and match the specs as closely as possible. I'm not sure if 6202TST001A is a Sunny designation or not. Searching on that gives plenty of hits.

PlainBill

[PlainBill]

Re: LG Flatron L1732TQ -Display "out of range"

Upon further review, try this one. XC1599CT-ND

PlainBill

[jarl]

Re: LG Flatron L1732TQ -Display "out of range"

Gentlemen... you did it!
I received the parts yesterday, and replaced the crystal last night. The monitor seems to be working fine right now Thanks!!!

Just one comment for any newbie that may land here in the future: the leads on the crystals are big (compared to other SMT components). So, when you try to desolder them it may take more heat than you may expected. I didn't pay attention to this and as a result I damaged (lifted) one of the pads underneath the old XC. I just used a thin cable to make a connection between the free lead on the XC and the nearest component on the same circuit (C108).

In any case, a big thank you for your patience and time.
Cheers!