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

[HellasTechn1]

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

Even better, start a new thread entirely since this is going to take some time to troubleshoot and not many people may be watching this thread since it's old....just a suggestion.

If the Mod's allow us ?

Yes i use your scheatic Dannyx.

Tommorow i will be away all day for work so ill be back with you on tuesday

Thank you all so much for your help i really appreciate it !

[Dannyx]

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

I think he's using mine, which was also generic, since there's a relay in there which wasn't on my board either....

[R_J]

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

I agree Dan, and maybe he could post the schematic he is using so we are on the same page, I have about 6 different versions of this PS schematic

[Dannyx]

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

Yeah some pics would definitely be welcome. Even better, start a new thread entirely since this is going to take some time to troubleshoot and not many people may be watching this thread since it's old....just a suggestion. Link it here so I can help you there too...really interested to get it going.

[R_J]

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

I wonder how can i identify the version of my board and find a correct diagram ? It says 17IPS20 but what version exactly ? how can i find out ?

If there was only a way we could see the board you are working on....
Is there a number printed in the corner near CN4 the black plug?

[Dannyx]

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

U300 is the main switching controller, generating 12/5v on the secondary, so it should definitely have VCC even with the TV off (board disconnected), since it's needed for stand-by. Vestel schematic are indeed extremely annoying to follow since they differ from the actual thing. Another way to figure out if U300 should be permanently "on" is to put your meter in diode/continuity/beep mode, whatever, and check for continuity between the VCC pin of U300 and that diode on the AUX winding - there should be continuity. There should not be continuity to HOT GND however - another thing you can check while you're at it. Since you have a scope and your life is MUCH easier than mine with this stuff, check for pulses on the gate of Q301 IF VCC is present but you're still not getting any output - it could be U300 needs replacing for some reason. I haven't seen a controller IC fail like that though, unless something went BANG rather violently or suffered a spike on the primary....

[HellasTechn1]

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

You are right.

Anyway is U300 supposed to be getting voltage while mainboard is not connected ?

[Dannyx]

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

AFAIK these Vestel diagrams show all possible components installed on them and you won't find one exactly for your version, so I'm afraid you'll have to work out yourself what is populated and what's not. Do you get those 13v at the VCC pins of the ICs ? That's what truly matters. Just because the capacitor I found shorted was near IC X, doesn't mean yours can't be some place else and you should only focus on what I tried.

[HellasTechn1]

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

Strange... Before i remove the jumper i meazured voltages again. take a look. very strange. All measurements arewith the DMM set to DC volts. U300 pin 6 reads 0v.
Also on my board S1 is open and a few capacitors are not installed. Ive noticed many differences between my board and the diagram. I wonder how can i identify the version of my board and find a correct diagram ? It says 17IPS20 but what version exactly ? how can i find out ?

[HellasTechn1]

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

Could be. Also looking back at the diagram i now realize why the voltage is not steady. The volage is semi rectified through the two diodes in serries. I will remove the jumpers and observe behaviour. then maybe i can locate the problem faster, like you did.

[Dannyx]

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

Not sure about the analog meter...those more tech-savvy with meters could probably provide the answer. Or it's simply not fast enough to register.

[HellasTechn1]

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

The anode of 214 is connected directly to the aux winding yes ? so from the anode to the ground i measure 1 Ohm (shorted) and from the cathode of the diode to the ground i measure 5 Mohm.

Again that is normal i think since the other end of the winding is connected to GND. i am only measureing the windings resistance...

[HellasTechn1]

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

Could be a short like I had, since what you describe is pretty similar...probe that same point in continuity mode and see if you get low resistance between it and hot ground. If you do, something's pulling that AUX output down...that would be my only explanation so far :|

I will. Also i assume the aux winding of the transformet is powered on all the time to provide stby voltage. Yes ? In other words it does ot require the mainboard to me presint.

Still why the analog meter reads nothing ? It is not dead that i can tell.

[Dannyx]

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

Could be a short like I had, since what you describe is pretty similar...probe that same point in continuity mode and see if you get low resistance between it and hot ground. If you do, something's pulling that AUX output down...that would be my only explanation so far :|

[HellasTechn1]

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

I am sorry to hear that brother. Everyone should have such tools.
I was lucky enough to have one from my father.

Okay i restored the diodes and fuse and now i am getting an unstable 5 to 5.3 volts from the D214...

Funny thing is that when i used my old analog multimeter it reads 0 volts at the cathode of d214... I am confused. Why would the DMM show reading while the AMM nothig ? (i have confirmed it can measure DC from an other psu.)

Ho and by the main filter cap reads 315 Vdc

I am calling it a "night"... See you tomorrow !

[Dannyx]

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

Well at least you have a scope as opposed to me ! Yes, the ground probe of the scope goes to earth, so you can't measure stuff on the live side without an isolation transformer or by simply lifting its ground pin from the outlet, otherwise something goes boom.

[HellasTechn1]

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

Awesome. Now how dumb can i be ?

I measured the cathode of d214 and got an unstable voltage from 2,5 to 3 volts. I wanted to use the Oscope to take a picture of it and i forgot that the negative probe of the Oscope is earthed...
Now i have a blown fuse and 2 shorted diodes Fixing it and reporting back.

[Dannyx]

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

Let's see if we can go over this, since it's been such a long time and can't remember it well. To make your life easier, when measuring "primary" "hot" components, you can grab your ground (negative probe) from the - leg of the bridge rectifier - it's nice and remote so you don't risk accidentally touching your probes and making a nice bang. So ground your probe on the bridge rectifier and now have a look at the schematic: attached to pin 13 of TR200 (use the search function to locate this) there's D214 which takes the VCC Auxiliary voltage and rectifies it, which is then used to power those three ICs I mentioned. Measure its cathode (output) and see if you get anything. If you don't, trace back even further: do you have voltage on the main capacitors ? Is this board getting any power at all ? Silly question: fuse ? Check the large gray resistors for the sources of the FETs - they should have low values and "conduct" (your meter should beep in continuity mode), though those seldom fail, unless the supply has experienced a particularly large spike on the mains and the FETs are toast....

[HellasTechn1]

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

when i measured the VCC voltage on U300 (6300A), U202 (6300A) and U101 (FAN 7529) the multimeter showed 0V.

I may have measured between the wrong pins. For U202 and U101 i measured between pins 4 and 6. Also the mainboard was disconnected...

Which are the aux windings pins ?

Please forgive me that i am really inexperienced and with little knowledge on electronics.

Thankyou.

[Dannyx]

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

Try to trace back the AUX winding where that VCC AUX is supposed to come from and measure from there.