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Old 05-13-2021, 07:41 AM   #1
Storyteller12
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Default Samsung Soundbar No Power

Hi, need some help here.
I have this smps for a n850 Samsung Soundbar that gets no output voltage.

I have check everything and found that Iím getting 390v from the main caps on the hot side. However there is an IC that needs 300v to turn on. There are (2)513 smd resistors in parallel that are supposed to drop the voltage from 390v to 300v. However the resistors drop the voltage to 190v through the first resistor and to 25v through the second.

I took both resistors out of circuit and both measure good 50kohms.

I plan on replacing them anyways but not sure that will solve the problem since they tested good.

Any thoughts or suggestions would be greatly appreciated. In the last picture I highlight the path to the resistors and ic I was talking about

Thanks in advance

Last edited by Storyteller12; 05-13-2021 at 07:56 AM.. Reason: Added picture
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Old 05-13-2021, 06:19 PM   #2
R_J
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Default Re: Samsung Soundbar No Power

How are you getting 390 volts on the main caps? I don't see a pfc circuit and the caps seem to be straight off the bridge rectifier, so it should be around 160vdc
The ic needs a VCC voltage, this will be across the small electrolytic next to the mosfet heatsink, If this cap is bad, the circuit will not start up.

Last edited by R_J; 05-13-2021 at 07:41 PM..
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Old 05-14-2021, 01:24 AM   #3
sam_sam_sam
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Default Re: Samsung Soundbar No Power

I would first replace the [email protected] volt cap and go from there but really you should just replace all the caps good quality caps and go from there except the two main filtering caps unless they are leaking then replace all of them
__________________
9 PC LCD Monitor
6 LCD Flat Screen TV
30 Desk Top Switching Power Supply
10 Battery Charger Switching Power Supply for Power Tool
6 18v Lithium Battery Power Boards for Tool Battery Packs
1 XBox 360 Switching Power Supply and M Board
25 Servo Drives 220/460 3 Phase
6 De-soldering Station Switching Power Supply 1 Power Supply
1 Dell Mother Board
15 Computer Power Supply
1 HP Printer Supply & Control Board * lighting finished it *


These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
2 Hem Saw Computer Stack Board

All of these had CAPs POOF
All of the mosfet that are taken out by bad caps

Last edited by sam_sam_sam; 05-14-2021 at 01:25 AM..
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Old 05-15-2021, 07:05 AM   #4
Storyteller12
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Default Re: Samsung Soundbar No Power

Thanks for all the reply’s. R_J you were right about the voltage. My multimeter was acting up and had to replace it.
Turns out it was the ic that was bad and stuck open. I have a new one ordered and just waiting for it to arrive.

The soundbar is fairly new. Only 2 years old so I don’t think the Caps need replaced but since I have it open I might as well right? What brand caps do you recommend?

Thanks again for the help
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