Logitech Z906 easy alternative power supply FIX/REPAIR

[joschyyyy]

Hello, my Logitech Z906 stopped working and now i wanna tell you how to fix it easily. I saw a lot of other alternative Power Supply Posts but i think, this method is the most simple way to do it. The Logitech Power Supply is not working anymore...

All you need:
- Audio Board (From the Z906 Audio-System)
- PC Power Supply (I'd say about 500W)
Shrinking Tubes and other Stuff arealso good..

On the Sound-Board you can see :
3,3V Keep Alive (small plug)
Ground (small plug)

+HV twice(bigger plug)
12V (bigger plug)
5V (bigger plug)
Ground twice (bigger plug)

I tried every other way to repair it(meassure Resistors and so on but it didn't work)

HOW TO DO:
On the main wires to the mainboard of the power supply you can short the green cable and a black cable(ground) to force the power supply to start.
Now you have to meassure which of the main cables provide 2x 12V / 1x 5V  / 1x 3,3V...
The 2x 12V are the ones you have to use for both +HV becouse it provides the most power...
The 5V you have to solder to the 5V and so on...
For the 12V+ you can/should use the Molex Plug. You also have to meassure which cables provide the 12V. Then you can solder them to the 12V Pin...
The next step is to solder the 3,3V Cable to the right Pin and don't forget the ground cable

You can remove the original Power Plug Cable then you can cut all not needed cables from the PC Power Supply and isolate them. After that you can lay the POWER SUPPLY cables inside. Last but not least you can seal the cable hole with hot glue. If you power it on now, it should work like in my case. Don't forget to power off the PSU after use!

Greetings!

I am not responsible if it comes to deamage or even a cable burn or other other deamages. Take care of yourself!

[Dinesh6252]

I don't have any idea on how were you able to supply that much volts from a PC power supply. The Z906 requires around 42V on the +HV pins which I think a PC PSU is incapable of supplying.

[TheMG]

It would work with 12V but the maximum output power of the audio amplifier before clipping will be greatly diminished. P=V^2/R, it doesn't matter that the PC power supply is capable of 500W, 12V peak-to-peak (assuming a single-supply full bridge audio amplifier) into whatever the speaker impedance is (probably around 4 ohms), is peanuts in terms of power.

To be quite honest, I wouldn't classify this as a repair. More of a hack to get the speakers working by someone who lacks the electronics knowledge and experience to either fix the original power supply, or at least find an appropriate substitute that actually matches the specifications of the original.

[RoGeorge]

I don't think it's a good idea to replace the power supply with an improvised one.  Repair the original one.

Have you check the thermal fuse?  That's what usually blows.

[Deeptarup]

HI

I have z906 speaker which is giving an usual problem -- whenever I turn on the speaker its getting off instantly. Its happening for last few days..what could be the problem?

[MathWizard]

I have an older but similar Logitech system, they use way less than 500W. Depending on the computer PSU used, it could cause issues if the load is too low. But for a quick short-term fix, I'm sure it beats no sound.


What problems did the Logitech PSU have ?


To Deeptarup, it could be something like the muting circuit. I know on my old logitech, the main output chips, have a little circuit that can mute the output, on startup, and when headphones were attached. And for thermal shutdown too, it did a thing like that.

Does is do anything at all ? Or just no sound?  If you crank the volume, is there hissing or anything ?

It could be a lot of things, from the PSU, to the op-amp's, to the output. Do you have a multimeter ?