The Image shows part of a Samsung 40" TV.
The 12.78VDC is the Mobo PSU.
The 145VDC is the LED PSU.
I am having an issue with the LED Drive chip.

The circuit looks like multiplier circuit !
My requirement is to decrease the 145VDC to around 70 to 80 VDC.
Is it possible ?
The SMSP does not have a stby supply but at "OFF" the 145VDC does decrease.
No way to adjust the primary is it would affect the 12.78VDC.

I can drive the LEDs but the MOSFET is getting hot at preferable brightness
I know it is PWM but the PWM chip is blown.
I cannot find a service diagram on the internet.
If you must know it is UA40J5000AK

 

What happenes if you put a capacitor on the Point B supply, and use that? Would it stay at 80V ish... Or use Point C and drop it down?

Otherwise your looking at altering the OVP feedback sensing circuit.

 

OVP is not an option.

I was wondering abt using point B, but I have no idea what would happen for the rest of the circuit.
By the way the feedback path is in the 12.78VDC area. No connection to the LED power area.

What happen if I joint B to D and separate the rest ( two diodes and a winding ) ?

 

if you join point B to D , as long as the transformer connection is not used, i would say it would work giving you approx 75V, just try it....

 

Hi,
Below is the link to find schematics of different models of television and amplfifier.

I Also took this link to this forum. During my readings in these forum anybody gives an idea on the link,
i copy the link address and save it. Please try
http://www.badcaps.net/forum/ REPAIRING TV ETC /CAPACITOR ISSUES

Http://KERESO-SERVICE MANUAL FINDER SEARCH

Http://MANUAL OWL.COM MANUAL SEACRH

These 3 sites would help you a lot in searching drawings.
It seems you are repairing an LED type televIsion, not CRT type

 

Hello,

@JUNELER , the links will not work as there are spaces in them.
Now the links are truncated and will lead to not found pages.

Bertus

 

Hi,
Below is the link to find schematics of different models of television and amplfifier.

I Also took this link to this forum. During my readings in these forum anybody gives an idea on the link,
i copy the link address and save it. Please try
http://www.badcaps.net/forum/ REPAIRING TV ETC /CAPACITOR ISSUES

Http://KERESO-SERVICE MANUAL FINDER SEARCH

Http://MANUAL OWL.COM MANUAL SEACRH

These 3 sites would help you a lot in searching drawings.
It seems you are repairing an LED type televIsion, not CRT type

LINKS DON'T WORK!!

 

Hi,
I just try the http://manual owl.com , yes not opening but google it it will open the site.

go to chrome and type manually http://manual owl.com if will lead to the site.

I just did it and works

 

Hello,

@JUNELER , You AGAIN have a space in the link.
It is now truncated and will NOT work.

Bertus

 

Hi,
I just try the http://manual owl.com , yes not opening but google it it will open the site.

go to chrome and type manually http://manual owl.com if will lead to the site.
I just did it and works

What part of YOUR LINKS DON'T WORK do you Not Understand!!!

 

@JUNELER Ur links does not work....as for the forum, I have no interest in registering.
If NET cannot gimme a hit on the service manual it is hard to find. If you cannot gimme a link don't waste time, as I have no interest in registering on forums beside AAC.

@Dodgydave I did what we both agreed and it is working.

Move the cap to the diode. Just removed the two diode and 1 winding is out.
LED Vcc is ~82VDC unloaded, drops to 72.4VDC loaded.
~2.83VDC per LED ( 24 LEDs )
~3.3VDC across Mosfet. Mosfet is cool.
Brightness is A-OK.

NICE...
One issue...Friggin Audio Chip is Blown.

 

Funny issue with PSU.

Primary PWM and Mosfet blew, took out a diode on the 12VDC rail, blew the fuse on the mobo, blew the LED PWM chip and now found the audio Chip is out.

Every thing in the 12V path blew.

By the way, there is one more TV with same issue.....!

 

@Riffa, whats the audio chip, maybe the voltage rail got a spike or mosfet shorted it out and then the transformer rebelled!!

 

Audio out is working, no sound from speakers.
It's Class D SMD, pretty difficult replace.

I believe it was a Surge