Samsung 215tw display cuts out

[almoodie]

Re: Samsung 215tw display cuts out

That seems to confirm it. The logic board is shutting down the backlights.

PlainBill

What can I do now.

[PlainBill]

Re: Samsung 215tw display cuts out

Blacklight comes on when monitor is first switched on but only for a second or so. This process can be repeated over and over.

Transformers
All values relative to ground
Primary resistances (to each of the three legs or the transformer primary)
1.6 ohm 9.0M ohm 9.0M ohm
1.5 ohm 9.0M ohm 9.0M ohm
1.0 ohm 8.13M ohm 8.6M ohm
19 ohm 9.0M ohm 9.0M ohm
7 ohm 7.2M ohm 7.5M ohm
1.4 ohm 7.5M ohm 7.7M ohm

All secondary resistances = 0.89k ohm

All return voltages R1 – R6 = 0.2 V AC

V1 = 0.012 V AC
V2 = 0.012 V AC
V3 = 0.012 V AC
V4 = 0.012 V AC
V5 = 0.012 V AC
V6 = 0.025 V AC


Connector to logic board voltages. Power on, all boards and display connected
ADJ = 0.9 V
GND
GND
GND
13 V = 13.35 V backlight on or not
13 V = 13.35 V backlight on or not
13 V = 13.35 V backlight on or not
Analog = 0.6V at switch on, rises to 3V when backlight dies
ON/OFF = 11V at switch on, drops to 3V when backlight dies

Al.

That seems to confirm it. The logic board is shutting down the backlights.

PlainBill

[almoodie]

Re: Samsung 215tw display cuts out

Blacklight comes on when monitor is first switched on but only for a second or so. This process can be repeated over and over.

Transformers
All values relative to ground
Primary resistances (to each of the three legs or the transformer primary)
1.6 ohm 9.0M ohm 9.0M ohm
1.5 ohm 9.0M ohm 9.0M ohm
1.0 ohm 8.13M ohm 8.6M ohm
19 ohm 9.0M ohm 9.0M ohm
7 ohm 7.2M ohm 7.5M ohm
1.4 ohm 7.5M ohm 7.7M ohm

All secondary resistances = 0.89k ohm

All return voltages R1 – R6 = 0.2 V AC

V1 = 0.012 V AC
V2 = 0.012 V AC
V3 = 0.012 V AC
V4 = 0.012 V AC
V5 = 0.012 V AC
V6 = 0.025 V AC


Connector to logic board voltages. Power on, all boards and display connected
ADJ = 0.9 V
GND
GND
GND
13 V = 13.35 V backlight on or not
13 V = 13.35 V backlight on or not
13 V = 13.35 V backlight on or not
Analog = 0.6V at switch on, rises to 3V when backlight dies
ON/OFF = 11V at switch on, drops to 3V when backlight dies

Al.

[PlainBill]

Re: Samsung 215tw display cuts out

[QUOTE=almoodie]

Razzy is probably right, it's most likely an inverter / backlight issue. Try hooking it up to a working computer, then shining a bright light on the screen while viewing it from an angle. If you can see the desktop or whatever the computer is displaying, that confirms it.

Hooked it up to a working PC and turned it on. I cannot see any image on the screen when I illuminate it with a flashlight.

Should I perform the tests outlined above or do I go in another direction?

I would say you may have to go in a different direction. However, there are a few things to try first. On most LCD panels you can see if the backlights are on from the back of the panel. If they are off, look at the back of the power supply / inverter. Notice the label by the cable that goes to the logic board. One of those lines controls the brightness of the backlights, the other turns them on and off. It APPEARS the two lines are the ones on the extreme left in the picture. Check if either of those lines changes state when the backlights goes off. If they don't, it IS a backlight / inverter issue, and follow the asteps in the previous post.

PlainBill

[almoodie]

Re: Samsung 215tw display cuts out

[QUOTE=PlainBill]Razzy is probably right, it's most likely an inverter / backlight issue. Try hooking it up to a working computer, then shining a bright light on the screen while viewing it from an angle. If you can see the desktop or whatever the computer is displaying, that confirms it.

Hooked it up to a working PC and turned it on. I cannot see any image on the screen when I illuminate it with a flashlight.

Should I perform the tests outlined above or do I go in another direction?

[PlainBill]

Re: Samsung 215tw display cuts out

Samsung 215tw.
When I turn the monitor on the video displays for a couple of seconds, then the screen goes blank. Power light glows continuously.
I opened it up. There are no bulging caps, but I replaced them all with the exception of the large 180 microF 450V.
Reconnected everything and turned it on again but problem remains.
No burned or charred components, and I can't see any bad solder joints.
Images of the power/inverter board are attached.
What should I do now?

Razzy is probably right, it's most likely an inverter / backlight issue. Try hooking it up to a working computer, then shining a bright light on the screen while viewing it from an angle. If you can see the desktop or whatever the computer is displaying, that confirms it.

There are several approaches to troubleshooting this problem, all with varying degrees of risk and chances of success.

The safest is to measure the resistance of the primaries and secondaries of the transformers. I would GUESS that the primaries will be under 10 ohms, the secondaries about 1K, but there is a LOT of guessing involved in that. With luck you can work from the top of the board, the output pins (labeled O1-O6) are covered with insulation. Do this with power off, of course.

A second approach is to hook everything together in some manner that you can access the bottom of the board while it is hooked to the monitor. While the monitor is displaying an image and the backlights are on, measure the ACvoltage from the returns lines (labeled R1 - R6) to ground (labeled GND).

A third approach requires the same approach as the second, but measure the AC voltage at points V1 - V6 to ground while the backlights are on.

In all three cases we are looking for a reading that is different from the rest.

Good pictures, by the way.

PlainBill

[Razzy]

Re: Samsung 215tw display cuts out

Can you barely see the image on the monitor? Could be inverter issue.

[almoodie]

Samsung 215tw.
When I turn the monitor on the video displays for a couple of seconds, then the screen goes blank. Power light glows continuously.
I opened it up. There are no bulging caps, but I replaced them all with the exception of the large 180 microF 450V.
Reconnected everything and turned it on again but problem remains.
No burned or charred components, and I can't see any bad solder joints.
Images of the power/inverter board are attached.
What should I do now?