Re: SyncMaster 740N strange lines
The bigger one has 5V in and 1.8V out. The smaller one (right on the edge) has 5V in and 3.3V out. I did not remove anything from the board.
gypsy
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Last Activity: 11-26-2010, 04:08 PM
Joined: 11-26-2009
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Re: HP Pavilion F1703 Purple Tint
Fixed it. The values in the EEPROM were all off (the values for 9300K and 6500K are still somewhat off as the original settings got lost in the power surge) but as I don't use those, it doesn't bother me much. You can of course calibrate it and set new values if you have access to the right tools (an example of such a machine is given in the manual in the white-balance section).
Make sure you use a clean input for this. Don't do what I did and try this while running F.lux at night - your final image will have weird colours and you'll...Leave a comment:
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Re: SyncMaster 740N strange lines
I reflowed both the VGA and panel connector (pictures taken before this was done) - no improvement. Note that this problem occurs even without a VGA signal, the OSD/no-signal screen exhibits the same issue.
Apologies for the inline posting. I've taken pictures of all boards, front and back, and attached them properly this time.
3,4,5 are the actual LCD driver board (attached to the top of the LCD).
6,9,10 are the power board.
7,8 are the LCD logic board....Leave a comment:
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SyncMaster 740N strange lines
The backlight had no problems staying on, but I opened it up to look just in case. The PSU looks like this (image reused from another 740N thread):
Same caps were blown, the infamous CapXons. 25V 820uF, replaced with Nichicon equivalents. The problem, both before and after the replacement, is [URL="http://www.youtube.com/watch?v=fjEHX9uqNAo"]THIS.[/URL]
Every time I power it up, the lines are different/begin in different positions, and are initially bright, then start fading to grey. Also, as you can see (compare the image with the reference on...Last edited by gypsy; 11-25-2010, 02:08 PM. -
Re: Benq FP71E/Q7C4 intermittent backlight
Resoldered most caps, transformers as you said, and the 4 transistors in question (after cleaning the board up a bit with 99% isopropyl alcohol), works fine and consistent now =)
Thanks for the advice, once again. Second monitor you've helped me fix =DLeave a comment:
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Re: Benq FP71E/Q7C4 intermittent backlight
Noticed some gunk around Q815, Q816 and Q808, Q809 (in between each pair of transformers) on the backside.. seem to be C5707 transistors, could that be an issue as well?
Also, missed the two fatter green Lelon 1000uF 10V at C712 and C709.Last edited by gypsy; 01-14-2010, 06:57 PM.Leave a comment:
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Benq FP71E/Q7C4 intermittent backlight
The backlight on this Benq FP71E (or Q7C4) sometimes works fine for hours, then suddenly dips in brightness for about a second, followed by the backlight going off completely; other times, upon startup, the Benq logo shows dimly and the backlight cuts out immediately. The screen remains on/does not go into standby. Usually, powering it off and giving it a few good whacks on the backside fixes it (the problem does not get resolved without the whacks), not sure what that could mean. I've taken out the power board and none of the caps look bulged, should I just recap them all? Could there be another...Last edited by gypsy; 01-14-2010, 06:44 PM. -
HP Pavilion F1703 Purple Tint
Hey everyone,
Apparently, this one's been through a power surge (it was given to me by a friend). Backlight is fine, OSD shows up fine (bright and all colours work), and if no input is connected, the LCD cycles full-screen RGB and white (see video), which is also fine. It has a single VGA input, I've tested it with a different cable to rule out a fray. On any VGA input signal, the screen has a blue/purplish tint to it, as well as significantly decreased brightness (not backlight-related, see pics below). I have MSPaint open in the pics/video, the background should be nice and white...Last edited by gypsy; 01-14-2010, 09:06 AM. -
Re: Samsung 930b LCD cold start problem (inverter?)
That fixed it! Bright as daylight and stable too. I reclaimed a $250 piece of hardware, thank you so much for the detailed advice and taking the time to look at my board =)Leave a comment:
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Re: Samsung 930b LCD cold start problem (inverter?)
I've checked the resistance on T301 and 302, it's identical. In terms of U202 and 203, they seem to be two ICs; Google search got me: Low-Voltage, SPST, CMOS Analog Switches. I've looked at the datasheet and tested continuity between all pins that are connected (save for ground), nothing - if I understand this correctly, they should be fine.
I'll hit up the parts store first thing tomorrow morning and let you know what happens. Thanks for all the help so far =)Leave a comment:
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Re: Samsung 930b LCD cold start problem (inverter?)
Correct, I get absolutely no backlight whatsoever. I found an F301 at the location you specified; it's shot. I attached a picture of it, looks to be 3A, not sure what the symbol beside it is. What should I ask for when I hit up the parts store tomorrow?...Leave a comment:
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Re: Samsung 930b LCD cold start problem (inverter?)
I wasn't using flash; however, my workbench light was pretty close. I've removed it and taken a [URL=http://varu.ca/top.jpg]top[/URL] and [URL=http://varu.ca/bottom.jpg]bottom[/URL] picture. The only place on the board where 13V is indicated is at the connector linking this board and the LCD's logic board. Tested it against ground (with everything hooked up).. 18.2V. Unfortunately, this is where my debugging knowledge stops (I know how to work a multimeter and soldering iron, but that's about it). I can't seem to locate a fuse,...Leave a comment:
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Re: Samsung 930b LCD cold start problem (inverter?)
I have the same issue with my 930b; I opened it up and found the three 820uF 25V Samxons bulged. Everything else looked fine. I recapped all electrolytic caps I could find on the board save for the large 450V 100uF just to be sure (put 35V 1000uF instead of the 25V 820uF Samxons... is this OK?). The screen portion works (no-signal box moves around if I hold a flashlight to it) and the green light is on and solid. However, still no backlight. I've looked on the back of the PS board, and there appears to be this white powder around...Leave a comment:
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