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Electronics => Repair => Topic started by: karlis77 on March 08, 2018, 08:15:32 am

Title: Issue with wireless loudspeaker MALONE at high volume
Post by: karlis77 on March 08, 2018, 08:15:32 am
Hi. This is my first thread at this forums so please do not be harsh.
I am just a novice in electronics, all my experience is in power supply design and stm32 mcu programming. No audio electronics experience.

The problem: Unknown model MALONE wireless loudspeaker randomly drops it volume after few minutes of playing music with highest volume. The volume drop happens randomly, like half of second it plays with no issues and then half of second the volume drops dramatically. This random volume change happens continuously.

Loudspeaker was working with no problems until it was used at max volume for like 4 hours. Afterwards these problems started to occur even after some minutes of playing.

My thoughts:
Time needed for this issue to happen makes me think that it is related to temperature, as temperature rise needs time.
When I dissassambled the loudspeaker I noticed that crossover network has high power resistor, which probably dissipates a lot of energy.
Right next to it there is a capacitor.
I think that this capacitor migh have been permamently damaged from high temperature when loudspeaker was used at max volume for 4 hours.
Anyway it seems strange that the random volume drop happens very sharply.

(http://i65.tinypic.com/16b11yt.jpg)

So, what do you guys think?
Thanks in advance.
Title: Re: Issue with wireless loudspeaker MALONE at high volume
Post by: anachrocomputer on March 08, 2018, 10:14:35 am
That NP capacitor has come unglued, possibly due to vibration.

Could you please post a detailed photo of the other side of the board? I suspect a bad solder joint somewhere.
Title: Re: Issue with wireless loudspeaker MALONE at high volume
Post by: karlis77 on March 08, 2018, 01:44:29 pm
Quote from: anachrocomputer on March 08, 2018, 10:14:35 am
That NP capacitor has come unglued, possibly due to vibration.

Could you please post a detailed photo of the other side of the board? I suspect a bad solder joint somewhere.

Ohh, I cut the glue to see the parameters of capacitor. I wanted to check if there is something similar available on electronics components distributor websites.
Title: Re: Issue with wireless loudspeaker MALONE at high volume
Post by: drussell on March 08, 2018, 02:56:53 pm
That is just the crossover board.  You need to look at the amplifier.
Title: Re: Issue with wireless loudspeaker MALONE at high volume
Post by: karlis77 on March 09, 2018, 08:14:36 am
Below you can see images of board which has rectifier, AC/DC and amplifier on it.
This is the amplifier used https://4donline.ihs.com/images/VipMasterIC/IC/SGST/SGSTS29620/SGSTS29620-1.pdf (https://4donline.ihs.com/images/VipMasterIC/IC/SGST/SGSTS29620/SGSTS29620-1.pdf)
Maybe it is some of the amplifier protections that kicks in.
I will try to wire it up and do some measurements.

(http://i64.tinypic.com/2prsrhz.jpg)
(http://i64.tinypic.com/vpvpq9.jpg)
(http://i67.tinypic.com/w9vbie.jpg)
(http://i65.tinypic.com/k9xhlj.jpg)
(http://i67.tinypic.com/2itj58m.jpg)