Samsung 242MP 5v standby but not turning on

[topgamer7]

I have 5v at the main board, but the monitor won't turn on. This is with only the main board and supply connected.

I tried connecting the power_on pin to 3.3v, which I can then test the other pins coming from the power supply, and they all read within a volt of expected.

From reading the service manual, I have tested for voltage at C614, FT670 and FT671.

If I test without the connection to power_on, I only get voltage at FT670 and FT671, which are both 5V.

If I test with the connection to power_on I get a reading of 12V at C614.

From my understanding I should only get the 5V readings because the tv is in standby.

And then the 12V reading is correct when it should be powered on.

I tried reconnecting the other boards to see if when I have power_on connected if the tv would be on, however I still get nothing on the screen or audio. Throughout all of this neither the green nor the red led have turned on (unless I supplied them directly with power).

I've inspected the caps on both the power supply and the main board and neither seem to bulge or leak. I don't currently have access to an esr meter to test them otherwise.

Anybody have any ideas? I've searched around the forums to see if there is anyone with a similar problem, but nothing seems to apply.

I would like to try to diagnose what is causing the power button or remote to not turn activate the other pins and turn on the tv, however I can't trace the main board very well, and I don't really know where to start.

[topgamer7]

Re: Samsung 242MP 5v standby but not turning on

From reading the user manual, it doesn't appear that the power light should be on during standby.

[Andrew F. Ali]

Re: Samsung 242MP 5v standby but not turning on

So.......you jumped the StdBy pin and the Pwr-on pins and all the voltages came up on the PSU? I hope you did this with the Main Board disconnected......then it would seem that you PSU is good.....If upon initial start-up the set powers and shutdown soon after in 2sec or so then you may have either an Inverter or CCFL failure......

[budm]

Re: Samsung 242MP 5v standby but not turning on

The question is do you have >2VDC on the POWER-ON pin when the power switch is activated, if not then the main board is not sending the Power-on signal to turn on the rest of the power supply, also as said by other, you have to disconnect the POWER-ON wire going back to the main board BEFORE forcing on the power supply with jumper or yo can damage the switched transistor on the main board, and never do the force on without using the resistor to limit the current.
You also need the BL-ON to get the backlights circuit to come on, some time it may also need the DIM control for the backlights too.

[Andrew F. Ali]

Re: Samsung 242MP 5v standby but not turning on

the question is do you have >2vdc on the power-on pin when the power switch is activated, if not then the main board is not sending the power-on signal to turn on the rest of the power supply, also as said by other, you have to disconnect the power-on wire going back to the main board before forcing on the power supply with jumper or yo can damage the switched transistor on the main board, and never do the force on without using the resistor to limit the current.
You also need the bl-on to get the backlights circuit to come on, some time it may also need the dim control for the backlights too.

+1

[topgamer7]

Re: Samsung 242MP 5v standby but not turning on

Alright, I will keep in mind I shouldn't leave the main board connected when testing the power on pin. And that I should use a resistor.

To answer your question no I do not get any voltage spikes on the power on pin when pressing the power button.

I figured that the power supply wasn't being activated after I checked that it could give the required voltages. I am having trouble tracing what components I need to test to see what would be preventing the on signal. I've tested the few components that show up near the function board from the service manual and they seem fine.

I've also taken a look at the function board and it seems fine as well.

[budm]

Re: Samsung 242MP 5v standby but not turning on

The command Voltage is static Voltage, <1VDC = OFF, >2VDC typ. = ON.

[topgamer7]

Re: Samsung 242MP 5v standby but not turning on

You are correct, there is an incredibly small voltage of 0.02 or so on ps_on

I read some of the information about the larger chips in the service manual. And found the connection from the function keys to the gm1601h-CF board. I found that if I probe that at the resistor listed for that circuit near the chip and press the power button I can see a drop from 3.3v to 2.5v.

This chip also has a connection to ps_on. If I probe that I get that same ~0.01v. However if I press the button I don't get a change. This would mean I need a new chip? Which probably means I would need an entirely new main board?