Logik L39FE12 39” Led backlit LCD TV

[dick_barton]

Fault:-
Noise originally coming from the bottom of the set after which set failed to switch on. No standby light.

Repair:-
Remove PSU from set disconnecting all cables leaving only ac power cord connected.
Mains ON/OFF switch found to be open circuit so shorted out for testing purposes.
AC voltage now present at bridge rectifier which now provides DC to UI via T2 ; but no 5Vsb.

Replace U1. 5vsb now up and running.

Short 5vsb to Pon and all supply voltages present. 5V, 12v, 24V

Re-Install power supply back into set and power up.
Front panel Led blinks very briefly as PSU voltages rise and fall every second. Pon, 5vsb, 5v, 12v & 24v all toggling high and low.

Removing the PSU once again and connecting Pon to 5vsb, I then loaded the +5v supply to draw 2 amps without any problems.

Has anyone further ideas or maybe access to the main AV board schematic. (MSDV3206-ZC01-01(B), 303C3206072)
Thanks

[CapLeaker]

Re: Logik L39FE12 39” Led backlit LCD TV

what is underneath that metal shield on the bottom of the main board?

[ReeceyBurger123]

Re: Logik L39FE12 39” Led backlit LCD TV

Common issue is the flash memory chip causing the psu to restart over and over. Try removing Ps on and turn the Psu on then plug into mainboard and see if it turns on.

[dick_barton]

Re: Logik L39FE12 39” Led backlit LCD TV

Hello CapLeaker,
Its the Tcon board according to images on the web.

Hello ReeceyBurger123,
Thanks for that. I'll let you know the result.

Regards

[dick_barton]

Re: Logik L39FE12 39” Led backlit LCD TV

Hello ReeceyBurger123,

The results of your suggestion have been positive and listed below:-

Removed CON4 as suggested.
Plug in TV and switch on.
Plug in CON4 -Blue light comes on and is steady.

Set works.

The set only works at the moment by plugging in CON4 after the set is switched on. If CON4 is already connected before being switched on, then the power supply cycles.

If you could offer any further advice I would appreciate it.
Thanks

[dick_barton]

Re: Logik L39FE12 39” Led backlit LCD TV

Prior to ReeceyBurger123 suggestion, I had removed the PON connection and powered up then reconnected PON to the 5vsb. The supply voltages would come up but the 12V supply would only reach 10.8V and not 12V and the set would still not work.

Taking this into account and my previous reply, would this point to still having a PSU problem?
Thanks

[dick_barton]

Re: Logik L39FE12 39” Led backlit LCD TV

Hello,
I'm completely puzzled as to why ReeceyBurger123's suggestion works i.e. powering up the set first with the DC connector from the PSU to the main board removed, swithcing on the set and then plugging the connector into the main board resulting in the set up and running.

But when the DC connector is in place and you power up the power led just flashes.

Could anyone offer me any further suggestions to help me move forward. Is this a power supply problem?
Regards

[ReeceyBurger123]

Re: Logik L39FE12 39” Led backlit LCD TV

I said that to see if the mainboard was not bring the Pson low with means it wont turn on, as when its connected seems like the mainboard is shot.

[dick_barton]

Re: Logik L39FE12 39” Led backlit LCD TV

Hi ReeceyBurger123
Sorry but I'm a little confused and hope you can bare with me.
Currently Pon is back in the connector and when switching on with CON4 disconnected and then reconnecting the set is working. So Pon does not appear to stop the set coming up.
Do you think it's still a mainboard fault?
Thanks for your assistance.

[dick_barton]

Re: Logik L39FE12 39” Led backlit LCD TV

An update.
Monitoring Pon the voltage is pulsing in line with all the other supply voltages. If I short Pin 9&10 (9= Pon, 10 = +5V) then the set goes into standby mode and can be switched on.
Thanks

[ReeceyBurger123]

Re: Logik L39FE12 39” Led backlit LCD TV

Thats what I meant, the flash Ic must have failed then.

[ReeceyBurger123]

Re: Logik L39FE12 39” Led backlit LCD TV

So looks like another one of these Umcs with failed flash Ic's. When it works does it give good image and sound ?

[dick_barton]

Re: Logik L39FE12 39” Led backlit LCD TV

Hello ReeceyBurger123
The picture is not too bad considering the price of the set when new and there is reasonable adjustment of colour, brightness, contrast, backlight.
The sound is what you would expect from small speakers but you can put it through your surround sound system if you wanted to.

You say "failed flash IC". What is the link between the Flash IC and powering up and can the IC be reprogrammed when the set is up and running via the USB?
Thanks

[CapLeaker]

Re: Logik L39FE12 39” Led backlit LCD TV

needs to be replaced and reprogrammed.

[dick_barton]

Re: Logik L39FE12 39” Led backlit LCD TV

Isolating the PSU from the TV I can apply 5vsb from a dc power supply while monitoring Pon.
When 5vsb is connected, Pon goes to 5V. Current drawn from power supply is 14mA.

In conclusion I now believe that I must still have a problem with the PSU so going to delve a bit deeper into it.

[ReeceyBurger123]

Re: Logik L39FE12 39” Led backlit LCD TV

You should replace the Ic then you will need to reprogram it pain in the ass to do though

[dick_barton]

Re: Logik L39FE12 39” Led backlit LCD TV

Hello CapLeaker,
How would one go about reprogramming the Flash IC, where could you locate the firmware. Please could you tell me how you came to that conclusion. I'm still learning and have just returned to TV servicing after many many years and firmware in TV's is all new to me .
Thanks in anticipation.

[ReeceyBurger123]

Re: Logik L39FE12 39” Led backlit LCD TV

The flash Ic is hidden under the main heatsink on this board pain to access as you have to desolder the whole heatsink.

[dick_barton]

Re: Logik L39FE12 39” Led backlit LCD TV

Thanks ReeceyBurger123,
Hopefully that will not be too difficult. However if I do remove it do you know how one goes about to reprogram it, where to obtain the firmware and how does this link in with the PSU.
Your advice is greatly appreciated.

[ReeceyBurger123]

Re: Logik L39FE12 39” Led backlit LCD TV

No worries mate glad to help, what is the full model of the mainboard buddy ?