Sabre LCT321BKA Help

[ivtec]

Hi guys; i found this tv out in the curve and it probably stayed out in the rain a few hours or even days,i got it home and used a Fan and a heat blower to dry it,i did power it up and first thing i had a blue screen with menu which was good news,screen was good,then plugged video sources and on all video sources had synchronize issues,see video pic;
then i blew hot air with heat gun towards the BGA and synchronize issue got worse,then i blew cold air with the fan and video got stable and now i have good video on all sources,i don't know how long before it goes bad again,!
what you guys think i should do?,i'm thinking of doing the same i did to my Vizio M42Vt that had scrambled pic by doing this see utube link:and installed a computer cooling fan blowing air to the BGA.

https://www.youtube.com/watch?v=hL9-eKZv_2s

this is the sync issues before i used blowing cooling air to the BGA

https://youtu.be/3KWKMW0mbbs

[vinceroger69]

Re: Sabre LCT321BKA Help

Maybe worth re flowing the bga ic with some added flux then add a cooling fan it may be a longer lasting repair then.

[ivtec]

Re: Sabre LCT321BKA Help

Maybe worth re flowing the bga ic with some added flux then add a cooling fan it may be a longer lasting repair then.

Thanks vinceroger; yes i did that and so far so good,i did not use flux though,
now it would be nice if i could find in the power supply 5v or 12v switched power,i can get the 5vdc but it's on all the time,i want to be able to turn off fan when turning off tv.

http://www.shopjimmy.com/megmeet-mlt...upply-unit.htm

[ivtec]

Re: Sabre LCT321BKA Help

Thanks vinceroger; yes i did that and so far so good,i did not use flux though,
now it would be nice if i could find in the power supply 5v or 12v switched power,i can get the 5vdc but it's on all the time,i want to be able to turn off fan when turning off tv.

http://www.shopjimmy.com/megmeet-mlt...upply-unit.htm

Here some pic of my Power Sup board MLT666

where could i connect the 12v fan to turn on and off with power button?

[budm]

Re: Sabre LCT321BKA Help

It looks like some of the caps under the heatsink of the power supply board have bulging tops, but I am not sure if it is due to the light reflection or not.

[ivtec]

Re: Sabre LCT321BKA Help

It looks like some of the caps under the heatsink of the power supply board have bulging tops, but I am not sure if it is due to the light reflection or not.

Thanks budm; the Tv is working now fine,can you please help me pointing to a voltage point where i can connect a 12v or 5v pc cooling fan behind the BGA chip so i can turn on and off with power button?

[ivtec]

Re: Sabre LCT321BKA Help

Budm here the Tv boards and connections

[vinceroger69]

Re: Sabre LCT321BKA Help

have you got a close up picture of the power supply wiring connectors and any printing by them so we can see what each pin is for.

[budm]

Re: Sabre LCT321BKA Help

Looking at the board, it looks like he 12V and the 24V are switched power source that only present when TV is turned on and PS-ON is present but you can easily verify by checking them when TV is OFF and when TV is turned ON. What ever fan you want to use, more likely will be 12VDC fan, get the one with the least amount of current requirement.

[vinceroger69]

Re: Sabre LCT321BKA Help

have you got a close up picture of the power supply wiring connectors and any printing by them so we can see what each pin is for.

Edit! forget the pictures ive just seen the shopjimmy link in post 3

[ivtec]

Re: Sabre LCT321BKA Help

Looking at the board, it looks like he 12V and the 24V are switched power source that only present when TV is turned on and PS-ON is present but you can easily verify by checking them when TV is OFF and when TV is turned ON. What ever fan you want to use, more likely will be 12VDC fan, get the one with the least amount of current requirement.

Thanks budm 12V and the 24V are present all times either with tv on standby or tv on,this is a different switch mode power supply,i tested all volts with tv in standby or on and voltages are present all times.
Well i've got a 12v adapter and built a manual switch that i have at hand to turn on and off fan.

Also despite tv was working ok,but to be safe i took your advice and tested all caps in the output of the switch mode power supply under the heat sink very hard to replace these but i did replace them all with used good old caps that i had in my scrap from tv boards that i find in the curve with just broken screens and all 1000uf and 470uf, 330uf, 100uf,10uf,about ten of them were completely dry,i wonder how could this tv work this way,luckily i tested this otherwise soon i would have lots of issues, thanks.

[budm]

Re: Sabre LCT321BKA Help

Are you sure the PS-ON is not stuck high? I do not expect the 24V for the Inverter board to be present when TV is OFF.

[ivtec]

Re: Sabre LCT321BKA Help

Are you sure the PS-ON is not stuck high? I do not expect the 24V for the Inverter board to be present when TV is OFF.

Thanks budm;i did not check after i replaced the caps in the output,i just closed tv and put the fan and connected an external 12v ps and that's it,i talked to a good tech and showed him this type of power supply and he said this is a switch mode power and all outputs are present all times on standby,in fact this tv has a manual switch behind tv.
I think the main board is responsible to disconnect all the power supplies to the invert-er

[budm]

Re: Sabre LCT321BKA Help

Yes the power supply is SMPS, but not all the suplies should all be on in stadnby mode since it will waste power.
When the TV is in standby, the only power supply that should be running is the standby power supply to run the main board, all other should be tuned off until the TV is turned on, then the main board will send the PS-ON signal to turn on the 24V power supply and the 12V supply for the audio section, then the main board will send the BL-ON signal to turn on the inverter circuit. The board also has PFC booster circuit which is turned on by PS-ON signal also.
So if all the Voltages are present then it is not normal.
The TV has hard power switch and soft switch (remote or power button).

[ivtec]

Re: Sabre LCT321BKA Help

Yes the power supply is SMPS, but not all the suplies should all be on in stadnby mode since it will waste power.
When the TV is in standby, the only power supply that should be running is the standby power supply to run the main board, all other should be tuned off until the TV is turned on, then the main board will send the PS-ON signal to turn on the 24V power supply and the 12V supply for the audio section, then the main board will send the BL-ON signal to turn on the inverter circuit. The board also has PFC booster circuit which is turned on by PS-ON signal also.
So if all the Voltages are present then it is not normal.
The TV has hard power switch and soft switch (remote or power button).

Thanks budm; do you think because all the caps in the output were bad caused the voltages to be present either in standby or on?
well i don't feel like opening the TV again to check that out,besides i ordered a Smart search protector to be able to connect TV in active plug and connect fan on the other plug so when i turn on tv it will turn on the fan.

[budm]

Re: Sabre LCT321BKA Help

If the power supply is stuck on then it will be exposed to surges and spikes 24/7 and also shortened the life of the lytics caps. best to use the hard switch to turn the TV off when not used.

[ivtec]

Re: Sabre LCT321BKA Help

If the power supply is stuck on then it will be exposed to surges and spikes 24/7 and also shortened the life of the lytics caps. best to use the hard switch to turn the TV off when not used.

Thanks budm;I've been using this type of Smart search strip on my Sony KV36HS500 with a fan on the back for more then 10 years and it never gave me issues,so i suppose this will not be any different!this one is a little bit different but it does same thing.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[ivtec]

Re: Sabre LCT321BKA Help

Hi guys Hi Guys;getting back to my repair my Sabre LCT321BKA as i said it's not that at the time it was not working OK but as i was trying to find the 12v to the external fan,i also did a check on some components in the power supply and luckily i did otherwise i would come up with issues,i'm sure this was the cause of the heating BGA issue !, story short i found out all these Caps see attach; were all completely dry,also did have to use my imagination how to put those caps in place without removing the heat sink and i came up with this tool from a pair of clippers,not bad for an amateur,hope this will be a help for anybody with this type of power supply.