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STB shutting off after a split second

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starLED

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I have a Set Top Box for TV (STB) that worked about two years fine, but now when I plug in adapter cable then power green light comes on for a split second then it shuts off, and no green on and red off light and LCD display is on.

I checked voltages randomly on board and there are 12 V, and adapter cable also measures 12 V.
STB model is NewGlee GL-c850AQ

What can be a problem?
IMG_20220430_153640.jpg
IMG_20220430_153651.jpg
IMG_20220430_153746.jpg
IMG_20220430_153731.jpg
 
STB box adapter is 12V 1A.
I tried two different adapters:
1) 12V 1.5A - same issue, green light power off after a split second
2) 12 0.85A - green light doesn't turn off, it flickers.
 
Last edited:
I was checking caps for short and I was wondering if this is normal.
Two caps near the main chip (CPU ?) have 072 ohms, and I was wondering can that be shorted to ground?
Other caps that I have tested are all higher then 500 ohms.
caps.jpg
 
I noticed there is a black discoloration on the bottom side of the PCB under the CPU (in red circle), it can't be seen good on the image.
Can that be the sign of a damaged CPU that overheated?
Also, caps in the circle also measure 072 ohms.
cpu.jpg
 
It's unlikely you can test the capacitors in-circuit, it's most probably reading through other parts of the circuit.

You could always remove one that you suspect?, and check it out of circuit - and also check across the PCB where it was.

Generally on STB's, it's either the power supply electrolytics, or it's scrap - there's generally no schematic, and no spares available. And quite often, if PSU electrolytics have failed, then the HT rail increases and causes further irreparable damage.
 
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