Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

[Dannyx]

Re: Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

Check this out.

[R_J]

Re: Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

Have you check the voltage on CN4 pin 3 ST_BY (this should be the power suuply on command from the main board) Check it and push the power button, see if it changes?

[HellasTechn1]

Re: Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

THANK YOU ALL so much.

I took a glance and got lost there in the diagram

Ill check for 3.3 but not tonight or tomorrow because i will be working all day.

I can tell that the mainboard is getting a little warm when connected and psu has mains. Not hot just a bit warm.

[Dannyx]

Re: Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

The first step is to determine where power comes in then work from there. See how the power rails are generated and check for shorts...sadly I suspect a dead CPU...

[HellasTechn1]

Re: Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

The first step is to determine where power comes in then work from there.

Do you mean the pins ?

See how the power rails are generated and check for shorts...sadly I suspect a dead CPU...

I am not sure what you mean here.

[Dannyx]

Re: Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

Yes, start from the pins where the power comes in and work your way inward from there. A main board doesn't run on the same voltage all throughout: the voltage coming in from the PSU is stepped down a couple of times to 3.3v and even 1v for stuff like the CPU and RAM - this is done either by linear regulators or by switching regulators. The part where a higher voltage is stepped down into a lower one should have a distinct area in the schematic: say 12v comes into Uxxx(where Uxxx could be a linear regulator or a buck converter IC) and 5v/3v comes out. Sometimes they may be "cascaded": it would be wasteful to convert 12v straight into 1v, so it's first stepped down to 5v or 3.3v and then stepped down again to 1v. All these rails need to be identified and checked with the schematic to see if they actually output anything. A schematic for a mainboard looks intimidating, yes, but half of that you don't even need to check because it's beyond what you can repair and what you care about: you don't care about the RAM, the EEPROM the HDMI all of that - you just care about having all the power rails "up" at this point. Since you have a scope, it should be a breeze, at least to call it definitively dead if not to fix it

[budm]

Re: Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

We still do not get the result of the post #62 request to know if the main board is sending the control signal or not.

[Dannyx]

Re: Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

I believe that is not possible due to no standby (no LED coming on), but only the OP (well I'm the OP actually but NVM) can confirm

[HellasTechn1]

Re: Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

We still do not get the result of the post #62 request to know if the main board is sending the control signal or not.

I believe that is not possible due to no standby (no LED coming on), but only the OP (well I'm the OP actually but NVM) can confirm

Im sorry i was away. Ill check and report back.

[HellasTechn1]

Re: Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

I confirm that 12V and 24V go to the mainboard while nothing goes from mainboard to the PSU.
Why is the PSU on without on/stby signal from the mainboard and how are 5V generated on the mainboard is not shown clearly on the Mainboard diagram attached in earlyer post.

Also i soldered the bad fan6300 that i removed from the psu on position U300 and despite the fat that is for feeding the LED driver it shorted out U202 and psu gave out no voltages. I guess thats because U202 is feeding u300 ?

At this point i just want to make sure that the mainboard is dead before i buy a new one and somehow veryfy that the psu is now ok for the same reason. I have already ordered a new fan6300 to restore PSU to full operational state.

[Dannyx]

Re: Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

Ok, so what's the state of this project thus far ? I see you've edited your original reply.

You can use the trick I mentioned earlier with feeding 12v from an external supply, although you should've at least got the standby LED to come on if its PSU is functional and outputs something like you said.

Page 5 of the schematic is what you're interested in. Follow the power from the connector on the left (either CN2 or CN3 depending on your model) and see where it "stops". Does your connector correspond with CN2 or CN 3 ? Do you get 12v and 24v where it's supposed to according to that pinout ? If not, check to make sure those lines are actually populated, since often with Vestels the pin is there but the components are missing, therefore you'll have no voltage present there either. For instance this particular board also shows the option for a DC adapter at the bottom of the page, which I'm betting is not what you have, so you have to identify what you're working with first. Vestel service manuals are generic and apply to all the different variants of that board instead of having dedicated individual schematics for each model....most confusing...

12vSTBY should go into U9 where it gets converted to 5v on pin 7 (after coil L3) - see if you get 5v. If you don't, see if that output (after L3) reads a short. If it does, something running off the 5vSTBY bus is shorted. To identify it, remove L3, connect a variable supply to where L3 used to be and gently increase the voltage (and current) being careful not to exceed the 5v rail and feel for where the board gets hot. Crank the current up as much as possible without exceeding 5v. The part that gets hot is your culprit. Repeat the process of tracing the power lines like this, from the input to the nearest DC-DC converter until you can provide more data. Everything you need of interest is on page 5 - don't bother with others just yet.

[HellasTechn1]

Re: Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

Ok, so what's the state of this project thus far ? I see you've edited your original reply.

You can use the trick I mentioned earlier with feeding 12v from an external supply, although you should've at least got the standby LED to come on if its PSU is functional and outputs something like you said.

Page 5 of the schematic is what you're interested in. Follow the power from the connector on the left (either CN2 or CN3 depending on your model) and see where it "stops". Does your connector correspond with CN2 or CN 3 ? Do you get 12v and 24v where it's supposed to according to that pinout ? If not, check to make sure those lines are actually populated, since often with Vestels the pin is there but the components are missing, therefore you'll have no voltage present there either. For instance this particular board also shows the option for a DC adapter at the bottom of the page, which I'm betting is not what you have, so you have to identify what you're working with first. Vestel service manuals are generic and apply to all the different variants of that board instead of having dedicated individual schematics for each model....most confusing...

12vSTBY should go into U9 where it gets converted to 5v on pin 7 (after coil L3) - see if you get 5v. If you don't, see if that output (after L3) reads a short. If it does, something running off the 5vSTBY bus is shorted. To identify it, remove L3, connect a variable supply to where L3 used to be and gently increase the voltage (and current) being careful not to exceed the 5v rail and feel for where the board gets hot. Crank the current up as much as possible without exceeding 5v. The part that gets hot is your culprit. Repeat the process of tracing the power lines like this, from the input to the nearest DC-DC converter until you can provide more data. Everything you need of interest is on page 5 - don't bother with others just yet.

Hello and thank you again. I had issues to attend these days so i have done nothing so far. Tomorrow i work all day so no time for troubleshooting the TV. On friday i will definetly give it a look and get back to you with more readings.

THANKYOU !

[HellasTechn1]

Re: Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

Good day to all !
I am now investigating the Mainboard voltage supply chips. Afer following your guidelines i have realized how important it it to be able to read a schematic and understand it ! Ill keep you posted.

[Dannyx]

Re: Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

Louis Rossmann got me into schematics and how to follow them. It helps in the realm of TVs as well - go check him out on Youtube if you haven't already.

[HellasTechn1]

Re: Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

I will short enough. As for the mainboard, there is a problem with the 3.3V. The 5V line is fine but the lm1117 reads short between the output and GND. The lm1117 is burned but it is not the only thing. after removing it the short was still there. ive checked all the chips i could and found nothing bad so the problem could be in many different places. So many circuits are powered from the 3.3_stby like audio, video etc. At this point i thought that i should order an other board.

[R_J]

Re: Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

You can apply 1-2 volts on that 3.3 volt line using a battery or current limited supply, and look for what gets hot, just apply voltage for a few seconds at a time. It might just be a small ceramic cap.

[petehall347]

Re: Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

i have a habit of poking around from original found short to other places . if both places shows short to next suspect you are very close .

[HellasTechn1]

Re: Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

You can apply 1-2 volts on that 3.3 volt line using a battery or current limited supply, and look for what gets hot, just apply voltage for a few seconds at a time. It might just be a small ceramic cap.

I did that before and came up empty. I just shorted the battery.

I doubt it is a ceramic because ive checked pretty much all of them on the board. I suspect the Audio chip or the main chip that gets warm when i plug the psu in. Most probably the 2nd like you suggested "getting hot".

[Dannyx]

Re: Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

A battery is not enough if something is shorted. You really need to pump that SOB full of amps to really get a feel for it - it's damaged anyway, so nothing to lose as long as you don't exceed that rail's nominal voltage, so if you're getting a short on the 3.3v line, you won't go higher than that.

[HellasTechn1]

Re: Dead Vestel 17IPS20 power supply repair (OK fuse, no shorts)

I did that also from my bench psu and the main chip got warm enough before it blew my psu 5Amp fuse.
I think its clear that the main chip is bad.