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

[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)

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.

[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 ?

[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)

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)

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....

[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)

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 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)

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

[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 !

[R_J]

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

Your board is a 17IPS20 060913R6, so that should be the schematic. These are a real POS to follow.
The circuit that needs to be working is the one for U202/TR200, it supplies 12V_AC to get 12v_DC which supplies +12VCC_S which supplies Q212 and gives +5V_STBY
TR200 also supplies VCC_MAIN, Q216 is a switch that controls VCC that supplies U300 etc. Q216 is basically controled by ST_BY from the main baord.
So you need st_by ON signal from the main board to have VCC on U300

[Dannyx]

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

Good spot...I couldn't tell the difference between U202 and U300...I think U300 is for the LED driver and it's "switched" (just like U101 for PFC) whereas U202 runs all the time to generate standby...damn

So yeah, with that being said you STILL need to check if the AUX winding outputs anything to power U202, then if it does see if you get standby, then if you don't trace everything back from there....such a pain in the butt...I much prefer a supply that's completely blown apart, at least you know what to replace at a glance

[dick_barton]

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

Can you confirm that VCC_Main as shown in post #23 is steady at 13.5V

[R_J]

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

I missed that in the picture, should have looked closer. thanks dick_barton

If you do have 13.5v on VCC_MAIN (VCC_M) You should have the other voltages from the transformer (24v_AC) which feed diodes to give 24volts on C213/217 and (12V_AC) which feeds D210 to give 12V_DC which goes through L200 to give +12VCC which gives +5V_STBY through Q212 (transistor acting as +5v regulator)

[Dannyx]

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

If you do have 13.5v on VCC_MAIN (VCC_M) You should have the other voltages from the transformer (24v_AC)

....provided the IC itself is operational, which it most likely is in this case, since those rarely fail without some damage on the primary first.

Still, if you DO get VCC_MAIN and nothing out the output, perhaps the IC is dead and not switching...scope to the rescue: probe its output pin that drives the transistor. Man, wish I had a scope right now

[R_J]

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

No, If the ic is NOT working you will NOT get VCC_MAIN. although it is drawn on the primary side it is a scondary winding, so no primary switching, no secondary voltage.

[Dannyx]

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

Yeah, it's been a while since I've tinkered with a Vestel.....I need to brush up on my SMPSs

[HellasTechn1]

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

Allright. Now before i go ahead and use the Oscope shouldn't i first disconnect the GND wire on the mains power plug ? i dont want to short anything again like last time...

Also to read the 13.5V i use ground reference right ?

[Dannyx]

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

Given what RJ said, yes, you measure VCC MAIN with chassis ground reference, since it's secondary (after a diode that should be there to rectify it, of course). Yes, lift the scope from ground - simplest way that I can think of to do that is to use an outlet without the earth connected or with no earth entirely...just for testing purposes. Correct me if I'm wrong - I did this myself when I had ground loop issues with an external sound card and my laptop: I plugged the laptop's power brick into a splitter with no earth and it was solved