Samsung LE37M87BD 37" powersupply board overheating

Thread Starter

demoz

Joined Mar 6, 2020
1
Hello everyone,

This is my first post, and i am looking for advices/opinions or should i actually call it a bit of help.
I started messing with solder iron/hot air gun as hobby couple months ago, bought few broken devices and managed to repair some.

After little introduction,

Here is the problem:

Old LCD TV will turn on for about 15 to 20 minutes, after that it will overheat and loose image - fading until black while backlight is still on.
Parts which are hot to touch (after safely unplugging and discharging tv) are colored with red on the image. Mainly transformer and "cooling radiators" to which are connected mosfets.

As precaution i have replaced capacitors that i could manage to find correct values (colored in blue on the image)

lcdpowersupply.jpg


Does anyone have any pointers on what should i check and how to determine faulty part or cause of overheating.
Looking at one mosfet it have white stains where the part/number should be written, just found out i could test mosfets with multimeter and will do within couple hours. Could faulty mosfet be the cause of overheating radiators & transformer ?

This whole procedure is mainly to learn and practice using solder iron, so any reply is appreciated :).

Oh, by the way, i have (you guys might laugh) tried punching few holes on the back side of the cover to see if better air flow will help it run longer or without interruption, yet got no luck out of that.
 

Dodgydave

Joined Jun 22, 2012
9,169
It's a Switched mode psu, those are the output diodes and pulsing transistors , ( hot side is primary mains) ( cold side is low voltage) it could be the loads on the outputs causing heat excessive current drawing.

You need to get the circuit diagram,.
 
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