Polaroid P40LCD12

[Daveatfernie]

Re: Polaroid P40LCD12

Tried forcing the psu in with the mainboard removed using a 470 ohm resistor but this was unable to start it either. (Connecting between 5v and power on input).
Still nothing other than 3.3 and 5v. The mainboard seems to be not trying to power the psu up.
The sw-switch input varies (sits at 5 when the mainboard is unplugged but raises to 7 with it connected). I'm unsure what this does and haven't traced it through the schematic yet.

I was thinking of trying to bastardise one of my other tv psus to power the board to see if it will fire it up. It's a shame there isn't a standard cable arrangement between psus. Until I can rule out the psu I'm at a loss to be honest as to where to have at.

I'll try the short between st_by and 5v tomorrow instead of the 470 ohm to see if there's any difference.

It also seems strange that if the mainboard is at fault(a psu on board the mainboard for example) that the indicator led isn't flashing (as the service manual indicates it should) there is no illumination at all on the power led.

[vinceroger69]

Re: Polaroid P40LCD12

ive had bad mainboards cause no power led dont rule it out. maybe budm or tom when there on maybe able to advise which pins to jump on the psu to check the other voltages etc.

[Daveatfernie]

Re: Polaroid P40LCD12

That's what I was thinking with the LED not being illuminated.
Ill try the psu shorting again, if there's no joy I'll start by getting a new psu.
If I can get the psu to fire up I'll get a mainboard.

Thanks again for all your help.

[CapLeaker]

Re: Polaroid P40LCD12

Here is the schematic on the power supply.
On PL816 (a 28pin plug) measure the voltages of each pin and report back.

[nomoresonys]

Re: Polaroid P40LCD12

so many unsolved mysteries, I'm guessing the power supply swap fixed it?

[AFajitas]

Re: Polaroid P40LCD12

[sweeney1987]

Re: Polaroid P40LCD12

Did you ever find out if it was bad power board or main board, have same tv with exact same symptoms
would help greatly if you told me.

Searching there is a repair kit for these vestal psus, would that be fault?

[ReeceyBurger123]

Re: Polaroid P40LCD12

Checked D893 ?

[sweeney1987]

Re: Polaroid P40LCD12

Checked D893 ?

Yes and gettin .47 of a drop from both it and D901

On further inspection there is a slight burn mark arond leg of D882 (anode side)
It and D883 are giving me readings both directions indicating theyre shorted
will try swapping them out first, thanks

[ReeceyBurger123]

Re: Polaroid P40LCD12

I have seen D882 or the one next to it go leaky in the past, they don't fully short but go leaky. The part on them in Mur460ax. Remove them off the board and check for leakage current sounds like the failure if the Pcb around them is burning also.