OK may have got sidetracked with the opto but not ruled out as a problem
Try this
No power to the board Meter on Ohms 2000 test S1 to S2 and S3 to S4
as marked on pic
1093 ohms between S1 and S2
1087 ohms between S3 and S4
1093 ohms between S1 and S2
1087 ohms between S3 and S4
Ok so the transformer seems ok
Next thing to test would be the lamps - do you have any spare ones or an old monitor or laptop
screen? If not perhaps try budms test lamp - see the 3rd link in his signature just above
Also when you have a pc connected and working when the backlights switch off can you see
a very dark image of what the PC is displaying - use a bright known picture that you can look for.
Perhaps shine a flashlight on the screen at an angle sometimes helps
i did mention in my first post didnt i, that nothing can be seen onscreen with flashlight even when connected to pc. and that the power led will flash every minute or so, along with a slight flash and quick to dim (hardly noticeable with the flashlight)
i did mention in my first post didnt i, that nothing can be seen onscreen with flashlight even when connected to pc. And that the power led will flash every minute or so, along with a slight flash and quick to dim (hardly noticeable with the flashlight)
after about 30 seconds of the green light on, it will make a slight buzz sound and flash off. then it comes back on and the screen flashes ever so slightly.
Update on the monitor. i still cant find out what the problem could be. it seems to me it could be lack of continuous power, but i'm not sure. i've checked voltage after the primary? transformer and the voltage doesnt drop.
if i have evrything except the display cable in, the backlights come on after a few seconds of high pitch noise, then after the backlights come on the high-pitch noise goes away.
if i have the display cable plugged in the backlights never come on and the high pitched noise doesnt go away, except when the power led blinks out ~ every 30 seconds.
though i have tried plugging in the display cable after the backlights come on, and the backlights stay on and the screen gets dimmer (maybe outputting black pixels?) but no menus come up.
CN101 from image IMG_0476 ash shown left to right are (with power in, connector unconnected):
0V, 0V (giving 5vdc turns on backlight), Ground, Ground, 5V, 5V, 12V
The backlight does light up my test lights no issue when i put 5v to pin 2.
dont know what the first pin is for though.
does this mean my logic board is certainly the culprit or is it still possible to be the power board?
with connector in and plugged in, measurements are as follows, left to right:
1.69V peaks 2V when power led goes off.
.04V peaks at .5V when power led goes off.
Ground
Ground
4.65V drops below 1V when power led goes off.
16.82V peaks at 20.5V when power led goes off.
Have you missed a pin? looks like the other 5v so as they are on the same trace it will be 4.65v?
Pin 1 may be the dim pin
Looks like pin 2 could be blon ( as it has no voltage and when fed with 5v test lamps light)
Do they stay on or just flash?
Do the proper bulbs light when you jump 5v to pin2?
Does look main board not sending blon signal.
BUT on the back of the per board picture there is a "blob" left side about 1 inch up
which covers the traces to pin1 and 2. Maybe worth looking to see if it is bridging them.
yeah, the 2 5V pins are the same.
i did also plug in the original lamps and force blon and they stayed lit as long as i held it there.
iirc, without looking i think that blob your talking about it a foam pad. besides pin 1 and 2 are receiving different voltages.
ok if its foampad otherwise check it. Try and trace back from blon and test any components.
Test the voltage regulaors on the main board and the voltage on the caps
Update! so i decided that caps are more often than not bad even though they dont look it. desoldered all the caps, measured them. all of them were high, some over 4ohms. replaced all with the best i got and now the power led comes on green and the backlight lights up, but the screen is black. i can turn the monitor on and off with the power button but never displays anything. even hooked up to pc to be sure.
so i'm guessing (as i've measured voltages) which i can see 12v (11.6) and 5v steady that the logic board has died from those voltage spikes from the bad caps. other than that it seems it could only be bad solder joint or can tantalum caps go bad too?
Comment