Polaroid P40LCD12

[Daveatfernie]

Hi all,
I've inherited the above tv. It has vestel gubbins, specifically a 17pw82-3 psu board and 17mb65s-3 mainboard.

When I push the buttons on the front of the tv there is a beep so 5 volts is there somewhere.

Am I better off starting diagnosis with the mainboard?

I can't see any poorly caps with my esr meter and have checked the components found in the online repair kits for the psu board.

Has anyone had experience with these TVs or these vessel boards?

Thanks in advance.

Dave.

[Daveatfernie]

Re: Polaroid P40LCD12

Having trouble with pics I'm afraid.

[Daveatfernie]

Re: Polaroid P40LCD12

Other pic.

[Daveatfernie]

Re: Polaroid P40LCD12

Any ideas anyone?

[sordids999]

Re: Polaroid P40LCD12

Have you checked voltages on the psu 24v,12v,5v etc ?

[Daveatfernie]

Re: Polaroid P40LCD12

Hi thanks for the reply,
I've checked and found 5V present, What looks to be 3V3. There is no 24V but it doesn't seem to have tried to get that far. I'm thinking mainboard at the moment. There are a few voltages generated on board so I'll see if I can probe for these.

I was interested to see if these particular Vestel boards had any known faults.

I get a beep from the buttons on the front when pressed and there's 5V to that PCB.

As it stands I've found the datasheet for the Boards and will try the voltage fail test points to see if it's complaining about any one in particular and will have a go at reflowing the SoC and memory chip on the off chance that it's a bad ball on the BGA. I can only hope.

It seems that this TV may only have been £200 new so am a bit reluctant to throw 60 pounds at a new maonboard and PSU board.

Thanks again.

[Daveatfernie]

Re: Polaroid P40LCD12

Hi again,
I've had a look through the schematics and what not and am a bit lost I'm afraid.

What controls what? Do you usually get a standby voltage that tells the main voltages on the power board to come up or should 24V 12 and the rest be present all of the time?

Can I connect the SW connector to 3v3 or 5 to get it to fire up without the mainboard there and if so do I use a link or resistor?

Regards

Dave

[Daveatfernie]

Re: Polaroid P40LCD12

Ive only been able to find 5 and 3V3 present on the power board.

[CapLeaker]

Re: Polaroid P40LCD12

Basically you have to find the 5V STBY and check if that voltage is going to the main board (which I think it is). Then you have to figure out, if the STBY voltage is coming back from the main board to the power supply, which turns on all other power supply voltages, while you "turn on" the TV.
So in other words: The only voltage always present is 5V.

[nomoresonys]

Re: Polaroid P40LCD12

Basically you have to find the 5V STBY and check if that voltage is going to the main board (which I think it is). Then you have to figure out, if the STBY voltage is coming back from the main board to the power supply, which turns on all other power supply voltages, while you "turn on" the TV.
So in other words: The only voltage always present is 5V.

how to check if STBY voltage is coming back from main board, is next step?

[Daveatfernie]

Re: Polaroid P40LCD12

On the output connector I can see:
SW_Switch output 7.425V
5VSTBY 4.8V
3.3VSTBY 3.3V

and no other voltages on the board conector.
As far as inputs I've found the ST_BY which I assume is the power supply on connector.
Everything else is an output from the PSU rather than an input from what I can see.
(Other than BL_ON, DIM, and A/D DIM).

Do you think I can 470 Ohm link ST_BY to 3.3V or 5 without the mainboard connected to see if it powers the board on its own?

Thanks again for your reply.

[CapLeaker]

Re: Polaroid P40LCD12

Either next to the ribbon cable that goes from the power supply, or in the schematic diagram of the power supply... there should be a pinout indicating name and voltage.

here is an older thread you may want to read:
https://www.badcaps.net/forum/showthread.php?t=38728

schematic:

[CapLeaker]

Re: Polaroid P40LCD12

I have seen power supplies were there was no writings on top, but rather on the backside of the board.
Sure you can jumper the power supply on, to see if power supply puts out all voltages.
I would do some more checks on the mainboard first, before I powered up the main board like that.

[Daveatfernie]

Re: Polaroid P40LCD12

Thanks I've cross posted onto this one as the other post was not resolved. That TV had a different fault as far as I can see as the PSU was powering up on it's own whereas mine stays in the standby mode. These are the schematics I was able to find also.

[nomoresonys]

Re: Polaroid P40LCD12

did you try unplugging the bl-on connector from power supply to main board, to see if back lights go on?

[Daveatfernie]

Re: Polaroid P40LCD12

Yeah, Nothing at all. With the any of the cables removed or not the PSU Never tries to power anything other than 5V and 3.3V.

I'm looking to buy a PSU and a mainboard but at the moment don't know which I'll need. Without testing that the PSU comes u pon it's own I can't tell.

Thanks

David

[nomoresonys]

Re: Polaroid P40LCD12

someone correct me if I'm wrong, seems if no back light after disconnect ps-on cable from g board to the a board, it's more likely a g board problem?

[Daveatfernie]

Re: Polaroid P40LCD12

I've tried to force the Sower supply to come up without any other board plugged in by connecting the ST_BY to 5V with a 10K.
I'm going to recheck the PSU board to see if I can see anything.

[Daveatfernie]

Re: Polaroid P40LCD12

I've double checked all I can (electrolytics and such) but to no avail.

I'm surprised if it is the PSU board that the ST_BY would not be at 5V or similar though trying to get the power supply to fire up.

I'll buy a PSU board and then a logic board.

Hoping that the screen itself is in good nick after this

[CapLeaker]

Re: Polaroid P40LCD12

Try to force the power supply on with a 1k Ohm resistor, if that doesn't work try just a jumper from 5V. 10k seems a bit too high.