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

[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)

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.

[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.

[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

[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)

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

[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)

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)

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.

[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?

[Dannyx]

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

Check this out.

[vinceroger69]

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

this maybe the mainboard service manual

[HellasTechn1]

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

I can confirm the 12V and 24V going to the mainboard but other than that i dont know.

Mainboard is VESTEL 17MB95M

[Dannyx]

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

It's possible the main board just uses 12v as standby and has no 5v output directly (the way mine did)...do you get any voltage going into the main board anywhere ? Could be a bad MB as well. Might want to search for a schematic for that board to see how power is routed around it (possibly a 17MB82s, though I may be wrong).

[HellasTechn1]

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

Great, q212 is not installed on my board. How can i locate the source of 5V ?

It may sound silly but is it possible that 5V come from the led driver circuitry ?

I also noticed that the connector diagram is not the same since pin 9 on the diagram is supposed to supply the 5v_stby but in fact it is not connected anywhere since q212 is not installed and so the jumper to it is also not installed.

[HellasTechn1]

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

Hmm. I now have 26v on d208, 12V on d209 d210 and d211, I get 12 and 24V on the mainboard. Still the TV will not turn on. No stby light nothing in general.
I do not see the 5V anywhere... Im going to check q212 but so far i have been unable to locate it on the PCB.
Does anyone know where is it located ?

Any ideas in general ?

[Dannyx]

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

The back of these Vestels is quite fat if I remember correctly, so it should fit no problem. Don't even bother soldering the "dead" IC back on the board - just try it out without it, see if you get startup and then install the missing IC for the backlight driver.

[HellasTechn1]

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

In first photo,top right,there is one mosfet.
Heatsink is too little,you can see almost burned PCB.
Encountered in few cases Q301 (if I remember right code) shorted G-S as result no backlight.
Also can see footprint for bigger heatsink.
I replaced original with another (big one) heatsink and Q301 from very hot now was little warm,so I reccomend to add a bigger heatsink to Q301.

Not a bad idea as long as the heatsinh is of low profile and will fit with the back cover installed.

[HellasTechn1]

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

I removed the old U202 and replaced it with U300 leaving U300 unpopulated and clean from solder residue.
Now i have the pulses on pin5 of u202 and also i have ac voltage from the transformers aux winding.
I am going to put the psu on the TV to see what happens. I expect it to power on but without backlight because from what i understand so far U300 is feding tr301 that provides 24V for the LED driver. Am i wrong ?

[gabiz_ro]

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

In first photo,top right,there is one mosfet.
Heatsink is too little,you can see almost burned PCB.
Encountered in few cases Q301 (if I remember right code) shorted G-S as result no backlight.
Also can see footprint for bigger heatsink.
I replaced original with another (big one) heatsink and Q301 from very hot now was little warm,so I reccomend to add a bigger heatsink to Q301.