Need help to repair Logitech z506 5.1 surround sound system

[maggi373]

I'm writing a little bad here because i'm in a hurry but i hope it's good enough

So i got this system in 2011/2012 and i think that this malfunction has been there always. I never noticed it last year when my powersupply blew. just been using the 5.1 not 2.1 sound stuff before it blew. But the thing is that after the repair i noticed this, and i was in school and my teacher hadnt much time to look into it, and i had other things to do so some classmates got the task to fix it and they broke those pads for those amps you see in the pictures, anyway but it wasent them (amps), they have been switched with new ones.

The malfunction is that the Rear left speaker (blue output) doesn't get amplified, it emits low sound. The other rear speaker does get amplified, or have a much higher noise, you can barerly hear the rear left speaker. I need help to localise what parts on the pcb can affect this, i'm new to electronics, i know the basic stuff, but not the higher end.

One pictore has some drawings, so i recomend to check that first, also i'm going to do some measurments of the voltage for the output

Link to pictures
https://goo.gl/photos/ECRt3WvENWWHmZJd8
These are central components
LM358
STA540
4558

[rg58]

Check the STA540 with an oscilloscope when all 5 channels are playing. Identify from which STA540 the failing output is coming. Then check the input of the respective channel (use datasheet for STA540). Inputs are on pins 4,5,11,12. If you compare the input level of the failing channel with the input level of a working channel, is the lower as well or is it the same? If the input is the same level but output lower, then either STA540 failed on this channel or there is a problem between the STA540 and the output socket (short? interruption?).

[maggi373]

I have replaced the ST540 myself not long ago, they are cheap and I thought it was worth a try but no, it seems that the problem is more weird than that, but few days ago the front left speaker shut off and does not anylonger emit sound, right before it sounded like it had a bad connection, like lifting the subwoofer upside down it got on again but now, nothing work. Just finished school so i no longer have direct access to an oscolliscope anylonger but i have friends that have, and in mid august i begin in school again, but I have UT61D (german verision) multimeter and a bench powersupply. The IC chip on the PSU blew again ca. a month ago. currently using a laptop charger at 19V to power it, know a good way to bring it 2 volts down?

If i have time i change the ST540 again just for fun, bought like 20 of them so why not

[keymaster]

I have replaced the ST540 myself not long ago, they are cheap

If i have time i change the ST540 again just for fun, bought like 20 of them so why not

20?? cheap?? i smell ebay . most likely you have 20 fake or rejected sta540. Buy only from reputable distributors ,so you don't chase your own tail .

[Rasz]

Z506 are pretty crap anyway
how about 3x $5 TPA3116 amps from china and call it done?

[maggi373]

re: keymaster: i used 30nok for each one, but got a discount if i bought 20 of them, but i had my doubt about the seller, but the problem were the same after i changed them with several other too but i'm going for a another solution maybe

[maggi373]

re: rasz: you mean those amp boards at ebay?
i'm thinking to buy something like this: http://www.audiophonics.fr/en/amplifier-boards/amplifier-board-tpa3116-class-d-6-voies-51-1x100w-2-ohm-5x50w-4-ohm-p-10090.html but i dont like it, it looks too cheap but it will do the work.

[Rasz]

or 3x http://www.ebay.com/itm/TPA3116D2-2X50W-DC-5-24V-Digital-Amplifier-Board-Class-D-Dual-Channel-Stereo-AMP-/282355075496

the less critical analog parts influencing quality the better. It still needs some fixing to remove the hum, chinese dudes cant read reference design apparently.

oh and dont think the one you found is designed/made in France just because its on nice "audiophonics" website, its chinese made by same company that makes this one:

http://www.ebay.com/itm/Full-remote-control-6-channel-5-1-channel-amplifier-board-TPA3116-M62446-50WX-/152571348334

[maggi373]

RE rasz i know that the board is from china, i found it on ebay first, but they had better pictures of the board. But your idea is a good way to go just need a to adjust the bass levels seperated from the center and a way to adjust the overall sound from one potentiometer

[Xero]

Have you fixed it?

I'm having same problem with my logitech z506, but with my front right speaker.
How do you fixed it?
What should I check?

[maggi373]

i never fixed it unfortunately however, i still have it and i'm now working with electronics as my job, so i can look into it, when i have time.

[magic]

If there is sound but it's just too quiet, I would start with checking all solder joints, resistors and capacitors around the opamps and power amp chips.
(This brute force method assumes you don't have a scope and can't find quickly where the signal gets lost).

When power amp chips fail, I would expect no sound at all or maybe distorted sound and possibly smoke from the chips or the speakers or both.

[Xero]

My problem start after I replace power supply with 12V 5A power supply.
It worked normal for 3 days.

After that I need to install that speaker on different computer, and I installed audio driver on that computer and plug the speaker in. And the problem started. Front right speaker emitting no sound . I turn knob to ~75%, it emit low sound. Turn knob to max, no sound again. And when I turn volume knob, it emitting zipping & crackling sound.
I have change the power supply with spec I find on youtube, power supply with laptop power supply that have output rating 19V & 4,7A, still having same problem. I already tried with other Logitech z506 front speaker that functioning normal, same problem.

Now, I still checking continuity around front speaker route on the soundboard. No blown caps.

[Bandi]

I think I found the issue on my z506 why there is not sound output at all to the RearLeft Speaker.
The elecrolytic capacitor seems to be defect. On the picture attached is a hole visible in the top area. I can not imagine the reason for such a capacitor. Strong pressure inside the capacitor would not lead to such a perfect hole.
I have also measured the capacitor, - no capacaty at all.


I have also compared to the pictures from "maggi373". He seems to have another issue.

I will write about my results after I have exchanged the capacitor

Update 2024.01.03
I have changed the capacitor and have now sound to the previously failed Audio Channel. PARTY
What a wonderful start for a new year