dell 172fpt 23v but no 5v

[PlainBill]

Re: dell 172fpt 23v but no 5v

I have done a bunch of resoldering.But I am unable to open any atatchments to see your suspect ones.May be tommrow?
Thank you Al.

I'm not having any problems opening the attachment to post #17. Are you?

PlainBill

[alexanna]

Re: dell 172fpt 23v but no 5v

Wow Its there now. There was also some one else that was having trouble opening attachments it must be fixed.
Al.

[kc8adu]

Re: dell 172fpt 23v but no 5v

i find it hard to believe that the 23v line is not only there but in regulation with the 5 gone.the +5 is where feedback comes from.and your lightbulbs cold resistance is likely to trip the ocp.are you sure you are testing at the correct point?

[alexanna]

Re: dell 172fpt 23v but no 5v

i find it hard to believe that the 23v line is not only there but in regulation with the 5 gone.the +5 is where feedback comes from.and your lightbulbs cold resistance is likely to trip the ocp.are you sure you are testing at the correct point?

Well I think so.
My ground lead is hooked up to the heat sink of the of the two schottky diodes ,D820 and D813
I measure continuity from the heat sink to the negative side of the capacitors for the 5v, and the 12v or 23v capacitors whatever it is suppose to be? The positive lead is hooked up to the center leg,O r # 2 leg. Of the diode.
I might be making a little bit of progress here .I have done some resoldering as PlainBill suggested. I have removed the thru hole components around the surge diode and resolderd them, Including the smps coil.
At this time my 5v has come back,The power Led is coming on,But after a very short time it starts to flash and I am noticing A squealing noise around the octocoupler.I haven't done it very long but the back lamps of my test panel will flash at the same rate as the power green led and the squealing noise.I still measure 23v on the center leg of D820 #yg902c2 diode.
I don't know if this got hit by lighting or there was a hell of a power surge,And its only a 17” monitor so how much time and money dose one invest? But I am not one to give up on things
I am unsure if any of the things I have mentioned will be of any help But at this moment this what's happing
Al.

[el3ctroded]

Re: dell 172fpt 23v but no 5v

The other diode next to d815... I'd replace it as well just cause it's cheap to do and in the same circuit.
And the transistor on the AL heatsink... test it carefully. I'd think it and/or the transformer T802 would be damaged. It may not be totally fried, just failing. Or it could be the pwm controller. If you have a scope, check the signal on the gate of the afore-mentioned transistor.

[alexanna]

Re: dell 172fpt 23v but no 5v

No to scope.But I should have enough spare good parts around here to try the other diode.I am just trying to keep the replacements to a minimum. the more i do the more of a chance I have of realy screwing some thing up.
Thanks Al.

[alexanna]

Re: dell 172fpt 23v but no 5v

Huston we no longer have a problem!!!!
I went ahead and replaced the thru hole diodes in the question area. no more blinking and or squealing and the test panel back lamps are working I have not hooked up lcd panel yet but at least I've got back lamps. I am reading a good steady 5v on one of the schottys. I am still reading around 23v on the other. I am going to let this run a little longer on the bench before I completely reassemble.
Thank you so much PlainBill and
kc8adu and el3ctroded.
Al.

[PlainBill]

Re: dell 172fpt 23v but no 5v

Huston we no longer have a problem!!!!
I went ahead and replaced the thru hole diodes in the question area. no more blinking and or squealing and the test panel back lamps are working I have not hooked up lcd panel yet but at least I've got back lamps. I am reading a good steady 5v on one of the schottys. I am still reading around 23v on the other. I am going to let this run a little longer on the bench before I completely reassemble.
Thank you so much PlainBill and
kc8adu and el3ctroded.
Al.

Thank me? I was spending the day in the pool!!! Glad to hear it's working.

PlainBill

[mips]

Re: dell 172fpt 23v but no 5v

I've been unable to locate a datasheet for the SMPS controller. Have you been able to find one?

Thanks to budm from https://www.badcaps.net/forum/showth...d=1#post213631

http://www.alldatasheet.com/view.jsp?Searchword=TEA1552
http://www.alldatasheet.com/datashee...S/TEA1552.html
http://www.alldatasheet.com/datashee.../TEA1552T.html