i inc 28inch monitor no power

[gustav]

Re: i inc 28inch monitor no power

Yep. Pin 1....0
Pin 2...0
pin 3 through 12....o

Also, I read up on how to measure those schotkzy diodes. One was to put the black probe on the BIG cap negative side, and the red on the middle pin of the Schotkzy, Power on. And the other way is to measure with the diode test pwr on. All i'm interested in to see where the power stops at. The inverter board is dead. I guess i will try to get thenew caps soon, but really wanted to find out if that is the only problem. I'm rather new to these newer LCD's and my electronic knowledge is constrained. Please bear with me on the learning curve.

[Rtech]

Re: i inc 28inch monitor no power

You had the led on earlier ??...but without any voltages on those connectors now,what has changed ??

[gustav]

Re: i inc 28inch monitor no power

The led is still on. I must be doing something wrong when measuring the pole(s). The led on the control board seems to work fine. Measuring I used the Black goes to a cold ground, red to pin(s). Dmm: DCV. 12 Pin CN on the Power Supply Board. Obsessed is the operative term.
I will do again underneath as well as on the pins.

[gustav]

Re: i inc 28inch monitor no power

Pin 1=0 GND. Pin2=0 PS(ON)
Pin 3=0 GND Pin4=5.1 +5 USB
Pin 5=0 +5 Pin6=0 +5v
Pin 7=0 GND Pin 8=0 GND
Pin 9=0 +12V Pin 10=0 +12V
Pin 11=0 ADJ Pin 12=0 On/Off

I was using a bad meter and ground. Got a different dmm and found a good ground. These are accurate readings. It looks like the 12V is bad. My Bad....

[PlainBill]

Re: i inc 28inch monitor no power

Pin 1=0 GND. Pin2=0 PS(ON)
Pin 3=0 GND Pin4=5.1 +5 USB
Pin 5=0 +5 Pin6=0 +5v
Pin 7=0 GND Pin 8=0 GND
Pin 9=0 +12V Pin 10=0 +12V
Pin 11=0 ADJ Pin 12=0 On/Off

I was using a bad meter and ground. Got a different dmm and found a good ground. These are accurate readings. It looks like the 12V is bad. My Bad....

The key is pin 2 - PS(ON). This monitor uses a dual power supply. The standby (+5 USB) supply is on whenever the power cord is plugged in. This provides power to the signal board. When you press the power button the signal board should send PS(ON) high (typically 3.3 volts), which turns the main supply on. One way to verify this is to hook a 3.3K resistor between pins 2 & 4 (with the signal card disconnected). The 5V (pins 5 &6) and 12V (pins 9 & 10) supplies should then come up.

PlainBill

[gustav]

Re: i inc 28inch monitor no power

Interesting PlainBill. Ill try it. Meanwhile, I checked out the caps with an Ohm meter. Found out that C210 and C211, both are 1000uf 35v, will not run up the meter like the others do. I guess this is a good possibitily they are bad. Also, will the caps at badcaps store work replacing the tricon caps? Thanks for the help.

[Rtech]

Re: i inc 28inch monitor no power

Now we are looking better,since the meter was sorted.Do plain Bills test and see what happens,because as yet, the caps have not been shown to be the problem.

[PlainBill]

Re: i inc 28inch monitor no power

"Will not run up the meter" is ambiguous. If the meter is on a high resistance range and never reacts when you touch the probes to the cap leads, that is a problem. If it hovers around some resistance in the 100 - 1000 ohm range, that may not be a problem. If it stays at 1 ohm on the 200 ohm range, that is a problem.

PlainBill

[gustav]

Re: i inc 28inch monitor no power

Ran Bills test with the 3.3k resistor. Here are the results:
Pin 1= 0 Pin 2=5. Pin 3=0
Pin 4=5.1 Pin 5=5.0 Pin6=5.0
Pin 7= 0 Pin 8=0 Pin 9=1.1
Pin 10= 1.0 Pin 11=.1 Pin 12=0

Put the cable on and stuck the resistor wires to Pin 2 to 4. and measured. And measured on the ps connector side pins as well as the pins under the board.
Oh yea, the light changes from green to amber after a few seconds.

Thanks PlainBill.

[Rtech]

Re: i inc 28inch monitor no power

So now then the problem is no 12v on Pins 9 and 10,so looks like that is the area you have to concentrate on.Either working back from the pins,or from the Schottky that it comes from after the input transformer secondary.

[gustav]

Re: i inc 28inch monitor no power

Got some readings. Looks like there's some shorts. Talke a look and see which ones need to find a new home. Or How to take better measurements .. Some diodes are bad, and wondering whatever could be damaged. Thanks

[Rtech]

Re: i inc 28inch monitor no power

Well without a schematic, and not knowing where exactly in the cct your diodes etc are,it is not easy.HOWEVER if D210 is mounted on a heatsink then its probably faulty.Notmally measuring Schottky's using the diode test,gives readings below 0.5 one way eg 0.177 etc, and the other way by revesing the leads,you would normally see the Caps that usually follow the Diodes charging,and the readings gradually increasing.It may help if you can advise the part codes on the devices that are mounted on the Heatsinks.

[gustav]

Re: i inc 28inch monitor no power

Well, here's the info i hope it will suffice. I tried to copy the http://www.alldatasheet.com/datashee...TP10NK60Z.htmlurls from alldatasheet

http://html.alldatasheet.net/html-pd.../STU407DH.html

http://www.alldatasheet.com/view.jsp...rd=STP4NK60ZFP

http://www.alldatasheet.com/view.jsp...word=MBR2045CT

By the way, what is the best way to accurately measure these MOFSETS. and schottky diodes? I am interested in learning on how to do it, so my knowledge will help in this endeavor. Your experience and understanding of my situation is vastly aprreciated


http://www.alldatasheet.com/view.jsp...word=MBR2045CT

http://www.alldatasheet.com/datashee...0CT-E3/45.html. I hope this will help. If I knew what to look for, i would be glad to post the info for ya. Heres the board pic with labels.

[Rtech]

Re: i inc 28inch monitor no power

The Diodes ending in CT are the Schottky ones,and follow the directions in the previous post to test..if necessary take them out of the board to test.The remainder are mosfets,and this may help you....
http://www.4qdtec.com/mostest.html

[gustav]

Re: i inc 28inch monitor no power

Well, ordered replacement for all of the schottky that's on the board as well as the caps. Got the Panasonic fr series. I went to Mouser's and chose Fedex and will get the parts tommorrow. That's 2 days with normal ground which is very quick. I will try to replace the parts soon. And hope this will take care of it.

I been learning all about schottky and transitors and testing as well, thanks to RTECH for the link and PLAINBILL's post on testing on the 2 second blank screen. Both were very informative.

Thank you for your guidance and patience. Your wisdom and knowledge is highly regarded by all on this site.

Be back shortly after the replacement

Thanks again

[gustav]

Re: i inc 28inch monitor no power

Well, replaced the caps and i'm still not getting 12v on cn pin 9. The D210 schottky was replaced also. I have two more to replace but my gut feeling is they're not to do anything. The pulled schottky looked good on the meter. I guess the big diode sitting aside the large cap will have to be pulled and checked.

If you all have any suggestions, please chime in.
Thanks

[Rtech]

Re: i inc 28inch monitor no power

IF you are certain that D210 is the 12v Schottky ??Then you need to try and break the 12v line as near to the schottky caps as possible,and measure across the CAPS then to check for the 12v,at source,if you see what I mean ?? just in case something later on in the cct is pulling the 12v down.

[gustav]

Re: i inc 28inch monitor no power

Well, I put the other schottky's and same thing: no display. I now replaced all the caps on the power supply board and all of the schottky's on it. Nothing. I do not know how to check for the 12v line to see if anything is pulling it down. The other options I haven't throughly checked are the transformers and all of the resistors and diodes. I about to fold it for the year. Christmas is creeping on us soon. And my time is coming near the end: Family responsibility.

Thanks all

[gustav]

Re: i inc 28inch monitor no power

well, there's a zener diode near the connector to the logic board. I'm getting a reading in one direction, but "OL" on the other. The other zener diodes on the board have a reading on both ways. Is this what I need to focus on? I need to find out what is needed so to order once or attemp to order everything I need. On some sites, they are asking 150.00 for a new board. On e-bay a China Site is asking 30,00 plus 10.00 for S&H. But it will take close to a month to deliver. Any suggestions?
Rtech mentioned breaking the line as near to the schottky caps? I really don't know what he means to do. I did check however, on cap with a dmm while it was on, any got nothing, the cap was replaced already.

Anyway, thanks again

[Rtech]

Re: i inc 28inch monitor no power

If you get nothing across the 12,volt smoothing cap immediately after the 12v Schottky diode,then either there is NO input to the diode, or something after the cap is pulling the 12v down,You need to break the line from the 12v cap positive terminal to the rest of the cct,so basically all you would then have in circuit would be the input side of the diode, the diode itself,and the cap,IF you then get 12v across the cap then the input and diode,and cap are fine, but something when you connect the rest of the cct is faulty.I presume when you are measuring that all boards etc are connected ??