syncmaster p2770hd no power to touch panel

[sdinelli]

Hello. this device does not turn on for me. no lights on the front panel.
My power supply voltages are all there.
pwm>>0V
13V>>13.25V
grd
grd
grd
grd
5.2V>>5.25V
5.2V>>>5.25V
5.2V>>5.25V
pwr_on>>0
DCR>>0
on/off>>0

I'm not getting any power out of the connector leading to the touch panel/ ir sensor in the front.
i guess I'm missing the "+3.3V_live" that leads to that.
Does anyone have the schematics to this? I already checked toms service manuals.
Also i believe i traced it to a bad voltage regulator but not sure.
the part says 17-33 1127BG and in dpak form. i removed it and broke a leg. lol\

The reason I thought it was this was because there was the 5.25V going into pin1 but was getting nothing out of pin 2 or 3.
Is it save to assume this was the cause? I'm not the best at trouble shooting curcuits.

can anyone help me find a replacement? couldn't find much details on this.
thanks

was going to replace with this one
http://www.digikey.com/product-detai...7-1-ND/3505302

[CapLeaker]

Re: syncmaster p2770hd no power to touch panel

pwr_on>>0 (PSU)
on/off>>0 (back lights)

At this point the monitor is off and the back lights too. Upload some high quality pictures of your main board so we can see something.

[budm]

Re: syncmaster p2770hd no power to touch panel

"17-33 1127BG' What DCV do you have on the 3 pins of the regulator with ref to GND?

[dskall]

Re: syncmaster p2770hd no power to touch panel

The 33 in part number may be the voltage of it and the 5.25v in sounds like you are on right track. Will need pictures to go further.

[sdinelli]

Re: syncmaster p2770hd no power to touch panel

"17-33 1127BG' What DCV do you have on the 3 pins of the regulator with ref to GND?

far right pin was the 5.25V
I believe middle and left pins were nothing. Something less then 5 mV maybe. I cant remember and I already desoldered it. the right pin broke off easy when removing.

[CapLeaker]

Re: syncmaster p2770hd no power to touch panel

So either the voltage regulator was bad or something is shorted on the regulator output dragging it down?

[sdinelli]

Re: syncmaster p2770hd no power to touch panel

So either the voltage regulator was bad or something is shorted on the regulator output dragging it down?

i noticed something that i wasn't sure if it was the design of the board or not.
pad 1 and pad 2 of where the regulator sits(left and center) has zero resistance between them.
does that sound fishy to you?

[budm]

Re: syncmaster p2770hd no power to touch panel

i noticed something that i wasn't sure if it was the design of the board or not.
pad 1 and pad 2 of where the regulator sits(left and center) has zero resistance between them.
does that sound fishy to you?

If you look at the IC with the tab up, left pin is GND (for this fixed output), middle pin /big tab is output, right pin is input.
So you may have shorted load, output filter caps, so remove the IC and check the resistance of the middle pin and GND again.
You should also look up the spec sheet of this 3.3V REG.

[sdinelli]

Re: syncmaster p2770hd no power to touch panel

If you look at the IC with the tab up, left pin is GND (for this fixed output), middle pin /big tab is output, right pin is input.
So you may have shorted load, output filter caps, so remove the IC and check the resistance of the middle pin and GND again.
You should also look up the spec sheet of this 3.3V REG.

I Had trouble finding the spec sheet for this exact regulator. cant even tell what brand it is. it just looks like symbols lol

I checked the resistance of the middle pin to ground. it fluctuated not going higher then .4ohms( not kohms)
the regulator beside it middle tab had .455 kohms

I measured R118 right behind the regulator in question
labeled 1R0 - measured 1ohm

[sdinelli]

Re: syncmaster p2770hd no power to touch panel

Well I ordered that 3.3V regulator in my first post so we shall see what happens.

[dskall]

Re: syncmaster p2770hd no power to touch panel

So you have short you will have to work out before replacing regulator

[CapLeaker]

Re: syncmaster p2770hd no power to touch panel

i noticed something that i wasn't sure if it was the design of the board or not.
pad 1 and pad 2 of where the regulator sits(left and center) has zero resistance between them.
does that sound fishy to you?

smells fishy, looks fishy, is fishy! Yes, you'd have to remove that short first.

[sdinelli]

Re: syncmaster p2770hd no power to touch panel

smells fishy, looks fishy, is fishy! Yes, you'd have to remove that short first.

I'm not sure exactly what to check because I don't the schematics but I guess ill try to poke around.

[budm]

Re: syncmaster p2770hd no power to touch panel

Remove the regulator then check the resistance between the middle pad and GND to see if it shows <1 Ohm or not as suggested in my post #8 which you did so it is not the IC that is shorted.
Can I see the closed up pictures where that regulator is? you may have to remove some caps next.

[sdinelli]

Re: syncmaster p2770hd no power to touch panel

Remove the regulator then check the resistance between the middle pad and GND to see if it shows <1 Ohm or not as suggested in my post #8 which you did so it is not the IC that is shorted.
Can I see the closed up pictures where that regulator is? you may have to remove some caps next.

The picture of the removed regulator is posted above.
Heres a closeup of the board with out it.
and the back side right behind it

[sdinelli]

Re: syncmaster p2770hd no power to touch panel

Does anyone think it could be the schottky diode on the back side?
it measured .067V and .04 V reversed.
I should probably remove it and retest huh?

[dick_barton]

Re: syncmaster p2770hd no power to touch panel

Diodes are best tested with at least one end lifted from the board.

[sdinelli]

Re: syncmaster p2770hd no power to touch panel

removed the schottky diode D103 from the back side
It says 106 B340
I measured .166V and OL reversed
this is no Bueno correct?
If it is indeed bad would this be a good replacement?

http://www.digikey.com/product-detai...DICT-ND/768811

Thanks

[dick_barton]

Re: syncmaster p2770hd no power to touch panel

Those reading appear to be good.

[sdinelli]

Re: syncmaster p2770hd no power to touch panel

Those reading appear to be good.

Ugh. I thought the voltage was supposed to be between .3 and .7 normally.