5.1 relay voice, no sound

Thread Starter

prerakk

Joined May 21, 2015
23
Hi Friends,i hope you all doing good :)

Friends i am having a problem with thid 5.1 home theater. It started with continuous relay sound few days back then today morning it is not giving sound output (in full volume it gives low volume sound)

So while checking the components when i put the ground of multimeter to ground of board and the positive of the multimeter to one of the transistor near relay pin (pics attached) it starts to work fine. But when i turn it on again, it doesnt work

I am new to on board fault findin so i unable to find the fault. If anyone have experience like, please help


Thanks in advance! :)
 

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sghioto

Joined Dec 31, 2017
1,553
Hard to tell without a schematic. The transistor in question (photo #2) has a 10K resistor connected to what appears is the base. This connection continues down to the left of said resistor to a connector at the corner of the board. I would check the traces on the pcb first to verify continuity.
 

MisterBill2

Joined Jan 23, 2018
7,234
If touching it with a meter probe makes it work, it might be an intermittent connection that can be re-soldered. So next try touching in the same place with a toothpick or other non-conductive item to see if just a touch makes it work. If you are able to solder well, with all the power to the thing off and disconnected, and that may solve the problem. But if you are not quite good at soldering do not try this.
 

Thread Starter

prerakk

Joined May 21, 2015
23
Hard to tell without a schematic. The transistor in question (photo #2) has a 10K resistor connected to what appears is the base. This connection continues down to the left of said resistor to a connector at the corner of the board. I would check the traces on the pcb first to verify continuity.

If touching it with a meter probe makes it work, it might be an intermittent connection that can be re-soldered. So next try touching in the same place with a toothpick or other non-conductive item to see if just a touch makes it work. If you are able to solder well, with all the power to the thing off and disconnected, and that may solve the problem. But if you are not quite good at soldering do not try this.
I
Hi thanks for reply. I check the continuity and it the component are soldered well. I think its could be relay problem (maybe) cause when i touch with non conductive it does nothing. When i try turning it on-off multiple times it does turn off.

Could it some prob with relay. Attach is relay pic
 

Attachments

Thread Starter

prerakk

Joined May 21, 2015
23
When the unit is working correctly does the relay engage to connect the speakers after a short delay?
Or does the relay only engage to disconnect the speakers if there is some kind of short or overload condition?
Its connect to the speaker quickly but only once its properly activated (the clicking noise that comes from it can tell if its properly activated ). When its not working , either the relay make no noise or it does does partially.

And the relay dont disconnect the speaker as long as its been manually turned off.when its working its working fine.
 

MisterBill2

Joined Jan 23, 2018
7,234
It is also possible that the relay is protecting the speakers from some problem with the amplifier, which is what it is supposed to do. If the amplifier has an excessive DC offset then the relay is not supposed to connect the speakers. So the problem might be with the amplifier circuit, not the relay circuit.
That is, the relay might be working exactly like it should. The problem may be elsewhere in the amplifier. THAT will require some testing to verify.
 

sghioto

Joined Dec 31, 2017
1,553
What MisterBill2 said above is very true it might be a whole different problem but there are a few measurements who can take with a DC voltmeter that should be able to verify if the relay circuit is at fault. Further examination of the top and bottom of the pc board shows a darlington configuration of the two transistors that drive the relay. I believe that circuit is similar to the one I'm posting below.
EEE speaker protect circuit.png
 
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