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Old 09-01-2008, 09:31 AM   #41
Crasoum
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Default Re: Mag LT916s Model 900p 19" LCD dropping like flies

Quote:
Originally Posted by orzo
This forum has been great! I appreciate the help.
One other thing. My monitor seems to be always on full brightness during the 2 seconds that it is on before the screen goes black. I took a while to operate the digital controls during the 2 seconds the screen was on, but I've painstakenly adjusted the digital controls down to 9 percent with no affect. Same behaviour: Cycle the power, screen comes on bright for 2 seconds, screen goes black, green power light stays on. My wife wants the kitchen table back, so if anyone has any ideas please let me know soon.
A back light could be dead, if a light goes, sometimes it causes over-resistance in the circuit and the circuit cuts power.
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Old 10-09-2008, 03:31 PM   #42
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Default Re: Mag LT916s Model 900p 19" LCD dropping like flies

Got one of these boards too, but only after it had failed totally. The person I got it from said it had the same intermittent problems at first before it failed dead (no leds, reads open, 220 input side fuse gone).

Cluster of 470-25 caps all swollen, 220-25 cap too. Replaced them with other caps from my recycle bin (don't ask). Could not find the right physical size of fuse, so replaced with a standard 3.15-250 using wire to stuff it somewhere else. Closed all up, applied power, nothing happens, still dead.

Opened it up, fuse is gone.

Removed 100-400 cap, it was flattened where it was glued, obliviously jammed in there hard - actually physically damaged. noticed the 0.43 Ohm (yellow, orange, silver) resistor above it (glued to the heatsink) was burned at the bottom.

Removed resistor, replaced with a 0.47 Ohm. New fuse, old cap. Close it up, apply power. *Bam*, fuse went catastrophically. Blackened some other components.

Replaced 25volt caps with new ones (470 and 220).

Replaced thr201. It broke off with the glue taking part of it with it when I removed the heatsink to clean it before installing 0.47 Ohm resistor.

Problem still seams to be on the ac input side. Other components seem ok. Replaced 100-400 cap (c201) could only find a fat one, not sure it will close..

continue tomorrow. other stuff to do
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Old 10-14-2008, 10:36 AM   #43
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Default Re: Mag LT916s Model 900p 19" LCD dropping like flies

Is it possible to get the schematic of LT916s power board...


Thanks

Surej
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Old 11-12-2008, 11:37 PM   #44
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Default Re: Mag LT916s Model 900p 19" LCD dropping like flies

I have some more information on these issues that may be helpful.
I have traced the problem to the feed back circuit on the inverter side of the board.
It may be that you replace all the Caps on power side and still see this result occuring. It has to do with the age of the CCFL's, they draw too much voltage and the feed back circuit detects this and shuts down the step-up tranformers on the inverter side. The CCFL's, however are still bright enough to last another couple years before needing to be replaced. There may be a way to fool the feedback circuit by removing a jumper wire, but I don't have a schematic to make sure. There are so many SMDs on board that the circuit is hard to follow, but I may put some effort into this as this particular power/inverter board is used in an array of different monitors.

The culperate being:
Mirage Electronics co, Ltd
AD-1700 REV:F
200-000-1700TL1 Version:A+

or some variety there of. The monitors I have encountered it in are:

Fujitsu Siemens C19-6 19" and 17" and other models
KDS 700P, 900P
Yakumo 700P 900P
Mag Inn LT782S
I also suspect it to be in some proview monitors as well.

If any of you can find a service manual with schematic for any of these, I believe I could tell you how to modify the feedback circuit. Good Luck in your repairs!
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Old 11-22-2008, 10:16 PM   #45
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Default Re: Mag LT916s Model 900p 19" LCD dropping like flies

Hi! I picked an LT916s that was tossed out at work. Initially it was totally dead. I repaired it in two steps. First I replaced the 6 - 470uf caps and the 1-220uF one in the section of the board near the rectifiers. All of these were "puffed out". At that point it exhibited the symptoms of 2 seconds on followed by blanking. Oddly enough it would come back on for another 2 seconds each time the video card was switched to a different mode, not just after a powerup. Next I replaced the 2 - 100uf and the 2 - 10uf ones. At that point it came up running. Thanks for getting me started in the right direction!
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Old 12-05-2008, 10:37 AM   #46
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Default Re: Mag LT916s Model 900p 19" LCD dropping like flies

I *think* I've fixed my ProView 900P. I'm pretty sure the cause was an oxidized lead on one of the 100uF caps causing a flakey connection that took over 2 years to show up. In general, I think these boards were built with "old" caps that had been laying around long enough for the leads to oxidize, preventing a good connection when they were soldered at the factory. This will effectively increase the ESR more and more over time until the circuit becomes dysfunctional.

My monitor has been up and running for a week now , whereas before it had the "2 second turnoff" problem.
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Old 12-10-2008, 10:51 PM   #47
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Default Re: Mag LT916s Model 900p 19" LCD dropping like flies

For anyone interested, I traced the entire schematic for the power - inverter board for the Mirage Electronics co, Ltd AD-1700 REV:F 200-000-1700TL1 Version:A+ which is used in all the monitors discussed.
I was actually impressed by the feedback protection circuit for the TL494 section in the inverter. I beleive now that it was well designed even if the power section suffers from bad hardware (caps).
If you replace the filter caps in the secondary and still have the shutdown problem, the most likely culperate is a failing or beginning to fail backlight.
If anyone is interested in the schematic let me know and I'll trade it for some other LCD schematic or service manual that you may have.
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Old 01-20-2009, 07:31 AM   #48
Herold
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Default Re: Mag LT916s Model 900p 19" LCD dropping like flies

Hello, Has anybody the schematic diagram of this tft monitor with the AD-1700 power supply inside.

Thanks, Herold.
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Old 02-01-2009, 08:48 PM   #49
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Default Re: Mag LT916s Model 900p 19" LCD dropping like flies

Hello... I have a 900p with this symptom and I am about to replace some of the caps on the power board... however, U102 (surface mount 8 leg... voltage regulator? I don't know what this part is) has 2 legs burnt black and the chip casing appears to be melted too, so I need to replace it. Where on earth do I look to find this part? It would help if I knew what it was.

I'm thinking the failure is related to the caps... a few have barely lifted tops. Is there anything more obvious that could have caused this part to blow? Can you help me identify what it is?
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Old 02-02-2009, 11:37 PM   #50
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Default Re: Mag LT916s Model 900p 19" LCD dropping like flies

Hello, my problem is a little different: I have a MAG monitor using the same inverter, my problem is when I turn on the monitor it doesnt work for about 8 minutes, then it turns on and works perfectly. I checked the boards and I dont see anything burned, any suggestion?
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Old 02-03-2009, 01:15 AM   #51
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Default Re: Mag LT916s Model 900p 19" LCD dropping like flies

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Originally Posted by huroni1
Hello, my problem is a little different: I have a MAG monitor using the same inverter, my problem is when I turn on the monitor it doesnt work for about 8 minutes, then it turns on and works perfectly. I checked the boards and I dont see anything burned, any suggestion?
I had the same problem (not 8 mins, just like 2~3) with a Proview 568, and I had to change ALL the caps in the Vboard, and it is working well right now.
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Old 02-03-2009, 02:52 PM   #52
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Default Re: Mag LT916s Model 900p 19" LCD dropping like flies

Why is this website called bad caps? Everybody starts replacing caps while the problem might be something completely different.
I also had the 2 sec. problem with a monitor with an AD1700 supply.
It turned out that the backlight stayed on when I disconnected the LCD from the main board. So only the backlight was connected via the CCFL wires. When I connected the LCD shielding with the main board shielding, the lights went out. With a multimeter I measured that one of the CCFL wires was in short circuit with the shielding. Probably the inverter supply shuts down after 2 seconds because of the leakage current caused by the short circuit.
I completely disassembled the LCD-display. It turned out that one of the CCFL wires was squeezed inside and the shielding had cut through the isolation, causing the short circuit (not visible from outside). I added some isolation tape and mounted the wire correctly. The monitor is working fine now. See also the CCFL photo with damaged wire (sorry that I had some problems with the macro function of my camera).
And about the bad LCD-display: It was manufactured by Quanta. Some time ago I had the opportunity to visit their headquarters in Taiwan which is very impressive. This production error was less impressive.
Have fun repairing your own 19 monitor, hopefully this explanation helps.
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Old 02-03-2009, 03:21 PM   #53
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Lightbulb Re: Mag LT916s Model 900p 19" LCD dropping like flies

Quote:
Originally Posted by dejonge
Why is this website called bad caps?
Well, because there are so many LCDs, Motherboards, Routers, and electronics in general PLAGUED with bad quality caps, that when are going down the drain drag something else with them. That's why.
I've repaired Samsungs where the problem was only one of the four CCFLs (17").
I've repaired 7 Planar PL150 so far with problems ranging from no display at all to random lines across the screen, that ended up being a bad ground connection on the input jack (all of them).Not a single cap was replaced.
I have repaired DVD Players, DVD/VCR combos and some LCDs (even the one I'm using to display what I'm writing, a VP201B) which the problem was a bad cap bank somewhere in there. Even Dell MoBos with their infamous cap problem have been fixed by me.
There are other causes for failure, but many times there are either only bad caps or components that had gone south because of bad caps or good caps under improper conditions (85c GP caps on a barely ventilated PSU, for example) that in the end blow away . I've seen it, and other have seen it. I think that's the reason why this whole place started.
Just my opinion.
And good for you that only with insulation tape were able to fix the LCD. I've been that lucky too in the past.

And Welcome to BadCaps
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Old 02-03-2009, 05:41 PM   #54
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Default Re: Mag LT916s Model 900p 19" LCD dropping like flies

Quote:
Originally Posted by dejonge
Why is this website called bad caps?
Because the owner replaces capacitors on motherboards for a living and that's what site is about.

He's nice enough to allow non-capacitor related electronics discussions in his forum.
Isn't that nice of him?

I think so.

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Old 02-09-2009, 02:23 PM   #55
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Cool Re: Mag LT916s Model 900p 19" LCD dropping like flies

I have a Hanns G 19" inch monitor i bought it second hand form a car boot. When I got the monitor home I plugged it in and the monitor worked for about 5 mins. Then it went blank. So I turned the monitor off and on and it then work for about 30 secs and then went blank again. So I took the monitor apart and saw that the power supply looked like it had got very hot as the metal around it was brown. I don't know if this is normal in a monitor. The power supply is 200-000-1700TL1 Version:A+. Also I have noticed that the 220uf 25 v capacitor is gone. What should I do, should I change the capacitor?
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Old 02-09-2009, 02:51 PM   #56
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Default Re: Mag LT916s Model 900p 19" LCD dropping like flies

The power supply is 200-000-170DTL1 Version:A+ not 200-000-1700TL1 Version:A+
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Old 02-09-2009, 04:00 PM   #57
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Lightbulb Re: Mag LT916s Model 900p 19" LCD dropping like flies

Quote:
Originally Posted by baileyboy
I have a Hanns G 19" inch monitor i bought it second hand form a car boot. When I got the monitor home I plugged it in and the monitor worked for about 5 mins. Then it went blank. So I turned the monitor off and on and it then work for about 30 secs and then went blank again. So I took the monitor apart and saw that the power supply looked like it had got very hot as the metal around it was brown. I don't know if this is normal in a monitor. The power supply is 200-000-1700TL1 Version:A+. Also I have noticed that the 220uf 25 v capacitor is gone. What should I do, should I change the capacitor?
Start a new thread with a title something like 'Hanns-G 19" turns off. Bad caps on PSU' or something like that, and post pics if possible. You'll get an answer that way.
I am fighting with a Hanns-G that does not have a PSU - like new, but PSU/Inverter is not there. Anything you need, you are welcome to ask.
And welcome to the forums.
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Old 02-09-2009, 04:56 PM   #58
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Default Re: Mag LT916s Model 900p 19" LCD dropping like flies

I have continued this in a new thread "Hanns-G 19" turns off. PSU overheated and bad caps"
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Old 02-09-2009, 05:02 PM   #59
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Lightbulb Re: Mag LT916s Model 900p 19" LCD dropping like flies

Quote:
Originally Posted by baileyboy
I have continued this in a new thread "Hanns-G 19" turns off. PSU overheated and bad caps"
Well, you got the idea ....now, open that thread!
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Old 02-12-2009, 12:26 PM   #60
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Default Re: Mag LT916s Model 900p 19" LCD dropping like flies

Hello Everyone,

The Mirage Electronics board noted in this thread - the 1700 - is available from Proview Technologies. I have a Sylvania 17" monitor that had similar symptoms... basically, at full bright it would go out after 5 minutes; at the lowest bright, after 15 minutes, it would flicker and make a gawd-awful high pitched squeal. The caps on the power board are NOT bulging or leaking.

They said they have a subsequent revision to the board that is in that monitor, so maybe they fixed the problems. I may also buy new CCFL tubes just in case.

Or I may say the heck with it and build that 96" HDTV projector I always wanted with the monitor parts...
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