Help Identifying a transistor / fault

Thread Starter

Dimis123

Joined Oct 3, 2017
11
Hi there, happy to be here, since this is my first post, so be gentle newbie here.
I have the following problem. I have a led controller with dimming functions that accept 7-16 volts and controls 10 high power leds in 2 parallel stripes (5 leds in series each). The problem arose by the appearance of smoke from the circuit.
I have identified the damaged transistors (which are 2 stp60n06-14) which after i replace them, one still reaches 100 degrees of Celsius in no time. Also i have notices similar temperatures on the diodes (60+)
The problem is that i do not have schematics and there are 3 transistors (q1, q2, q4) that i can not identify which i believe might be the reason for the problem. Or you might have a better idea on what could be the problem.


Regards20170901_081519.jpg 20170901_081501.jpg 20170901_081528.jpg 20170901_081557.jpg 20170901_081631.jpg 20170901_081714.jpg

Any ideas what these might be?
 

Dodgydave

Joined Jun 22, 2012
10,366
Looks like it's a pwm dimmer circuit or voltage control, using a TL494 chip, the Lm358 is an op amp comparator.

Ideally i would trace out the circuit around the mosfet and back to the chip to see what's happening...
 

Thread Starter

Dimis123

Joined Oct 3, 2017
11
Yes it is a pwm dimmer as far as i know, but i do not know know if this side of the pcb is responsible for the pwm dimming or the voltage control of the input.
Could the problem start from the input voltage control (it is capable of receiving 6 to 17 volts) and output 7,4v to feed the leds which does not make senses since there are 2 series in parallel each one consisting of 5 hi power leds (cree maybe) in series.
Forgive me if i am mistaken newbie :)
 
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