PI-190DTLB 5v earthing out

[sabre504]

Re: PI-190DTLB 5v earthing out

Have you checked Q201

[SuperDuty]

Re: PI-190DTLB 5v earthing out

Just checked, no problem there either.

Once again, did some soldering, powered up the thing, it worked (no panel on), unplugged it several times and now it worked each time. Checked the voltages, I got 4.98V at the +5V and around 15V at the +14V.
But I put it aside to plug the VGA cord to see if it was detected by my computer and the power wouldn't come back...again.

[selldoor]

Re: PI-190DTLB 5v earthing out

Hi - in an earlier post R 233 and R234 were mentioned and yo said you had replaced the
resistors. Whilst you may gave soldered the new resistors to the pads I am wondering if the pads should be soldered together - as your picture is posted in line I cannot easily enlarge it enough to tell) It could be that as you move / heat the board the pads are touching then as it cools/moves it is not touching. Please check again and if they should be connected re solder them and if they shouldnt then make sure there is a gap.
I am assuming the loose screw shown at the side of the board has been removed

[SuperDuty]

Re: PI-190DTLB 5v earthing out

I've just removed the two resistors and they're joined, so they're supposed to be soldered together. Resoldered them and no go.

And yes, the loose screw is back where it's supposed to be

Could it be a bad transformer ? AFAIK, those are pretty simple and there's not much that can go wrong with these parts.

[selldoor]

Re: PI-190DTLB 5v earthing out

I have read today a thread where the pson pin had become unsoldered from the
board but connected from time to time. - Long shot (very) but worth a look?

[SuperDuty]

Re: PI-190DTLB 5v earthing out

Well I reapplied a bit of tin on the PS on pins and transformer pins, and it worked. I plugged it to my computer and could see that the backlighting is not working, but I could see the windows on the panel.
Then I let it sit off and unplugged while I looked for another panel, and it wouldn't turn on...

So I melted the solders at the transformers pins and it came back. And it seems to have done the trick, so far I've let it sit much longer than before and it turns on as it should.

Now the other problem is the backlighting that doesn't work : i've tried with another 19" panel and several spare CCFLs I have and none would light up.
Maybe it's the same problem as with the main transformer. I will melt the solder around the two smaller transformers.

EDIT : didn't work again after letting it sit, melted the solder, and it's back on. WTH is that ! Did the same to the solder point where the transformer for the CCFL are...and it works fine now.
So I'm guessing either the original solder was of extremely poor quality, or I don't know really. It's flickering pretty bad after about 30seconds, capacitors ?

[selldoor]

Re: PI-190DTLB 5v earthing out

Does the screen flash at all?

EDIT ok see your edit. - Great
1. Try and turn the brightness down see if that helps.

2. test it with your other bulbs /panel to see if it is bulb/wiring related

[sabre504]

Re: PI-190DTLB 5v earthing out

Have you tested the two components ringed in yellow as you have some bad scorching on the upper face of the board

[SuperDuty]

Re: PI-190DTLB 5v earthing out

Yeah it seems to be working fine now, no dead pixels, no flickering, there's a gentle hissing sound on start up but it's slowly vanishing.
The brightness of the screen is a bit dull though, not sure if it's the screen itself or the power board. I'll try with another panel to see if it changes anything. And I'll let it sit too, hopefully the problems are gone for good now.

EDIT : I have tested them on the board (I haven't removed them) and the results were fine and identical for both. But I guess since the screen works now, all the components should be fine.
EDIT : doesn't work with the other panel at all, I guess they're not compatible. Put back the original one an it started just fine. It has some trouble starting up though, it takes about 30sec before the hissing and flickerings go...

[SuperDuty]

Re: PI-190DTLB 5v earthing out

To all the ones with the same power supply in their screen, if replacing the dead components doesn't work, just resolder all the transformers with new tin. It has done the trick for me. These seem to heat up a LOT (seeing how the PCB turned black in some spots), the original solder must have become porous or at least not fully conductive. Kinda weird.

EDIT : AHHH, spoke too fast, I let it sit for about 20minutes, and no power Heated the solder on the transfomer, and it's back alive. I'll remove it, clean the solder and put it back with brand new tin.