(thread copied from this one posted by mistake in the TV forum - please reply here)
OK I know this probably ain't the best quality monitor in the world, but I got it non-working for almost nothing, and getting it going has turned into a bit of a personal challenge. It came totally dead, but after changing the power mosfet, a couple of resistors and the PWM I/C it now lights up (I guessed that the blown SM resistor in the first pic below read 471, and soldering a 470 ohm 1/4 watt resistor over the top seems to work), but I just get a white screen.
Now looking at this thread on the Samsung Synchmaster and the earlier HP thread it refers to, it seems likely that there is a problem with the T-Con board. I've been through and tested all the caps I can recognise and none seem to be shorted (damn those oh so similar looking SM inductors for the hopes they gave and took away), and measuring the likely test points gives me the following readings:
VDDD 30KOhm 3.3v
VDDG 100KOhm 24.2V
VEEG 146KOhm -6.6V
VDDA 8KOhm 13V
There are a bunch of test points in the top right labelled POL, LP, VCOM, STH_F, VDDG_FLK, XDON, OE, STV, CLKV which all read open wrt ground, but I'm not sure if they are relevant.
Or have I got a problem on the video board itself? I'm not quite sure where to go now.
New in this thread:
FU101 tests fine for continuity. I've since found a service manual for download, and it looks like the boards inside this monitor were also used for the Viewsonic JT229ZP6MR, but here they've put in a 20" panel with the same resolution and sold it under a different name.
Service procedures for no picture are however a bit limited. First check I105, the big PQFP-128 chip in the middle. No mention of how, and that's a bit beyond me anyway. Then check the socket, then the cable. If those check out fine then look at the crystal oscillator. The cable I've pulled and given a good clean with an eraser, the socket, well what can one do? slide a cleaned cable in and out a few times?
Now I think both the big chip and the oscillator are OK, because of the way the screen behaves when I switch it on. Plugging it in with no VGA cable attached gives me a white screen for a couple of seconds before it goes to standby. Attaching a VGA cable means that the backlights stay on, so presumably that main chip is controlling that backlight and not dead. Leaving the monitor on for a couple of minutes gives me a greyish white (i.e. not 100% bright) all over the screen apart from a thin stripe of white 1-2 mm wide about 50 mm in from the right hand side of the screen. Now wouldn't the crystal be needed to get the timing for a "feature" like that.
So now I really have run out of ideas. And there's not much on the main board to test. All the big inductors and caps on the left are part of the audio circuitry for the built in speakers.
OK I know this probably ain't the best quality monitor in the world, but I got it non-working for almost nothing, and getting it going has turned into a bit of a personal challenge. It came totally dead, but after changing the power mosfet, a couple of resistors and the PWM I/C it now lights up (I guessed that the blown SM resistor in the first pic below read 471, and soldering a 470 ohm 1/4 watt resistor over the top seems to work), but I just get a white screen.
Now looking at this thread on the Samsung Synchmaster and the earlier HP thread it refers to, it seems likely that there is a problem with the T-Con board. I've been through and tested all the caps I can recognise and none seem to be shorted (damn those oh so similar looking SM inductors for the hopes they gave and took away), and measuring the likely test points gives me the following readings:
VDDD 30KOhm 3.3v
VDDG 100KOhm 24.2V
VEEG 146KOhm -6.6V
VDDA 8KOhm 13V
There are a bunch of test points in the top right labelled POL, LP, VCOM, STH_F, VDDG_FLK, XDON, OE, STV, CLKV which all read open wrt ground, but I'm not sure if they are relevant.
Or have I got a problem on the video board itself? I'm not quite sure where to go now.
New in this thread:
FU101 tests fine for continuity. I've since found a service manual for download, and it looks like the boards inside this monitor were also used for the Viewsonic JT229ZP6MR, but here they've put in a 20" panel with the same resolution and sold it under a different name.
Service procedures for no picture are however a bit limited. First check I105, the big PQFP-128 chip in the middle. No mention of how, and that's a bit beyond me anyway. Then check the socket, then the cable. If those check out fine then look at the crystal oscillator. The cable I've pulled and given a good clean with an eraser, the socket, well what can one do? slide a cleaned cable in and out a few times?
Now I think both the big chip and the oscillator are OK, because of the way the screen behaves when I switch it on. Plugging it in with no VGA cable attached gives me a white screen for a couple of seconds before it goes to standby. Attaching a VGA cable means that the backlights stay on, so presumably that main chip is controlling that backlight and not dead. Leaving the monitor on for a couple of minutes gives me a greyish white (i.e. not 100% bright) all over the screen apart from a thin stripe of white 1-2 mm wide about 50 mm in from the right hand side of the screen. Now wouldn't the crystal be needed to get the timing for a "feature" like that.
So now I really have run out of ideas. And there's not much on the main board to test. All the big inductors and caps on the left are part of the audio circuitry for the built in speakers.
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