Logitech X-230 PC subwoofer powerless

[steves7839]

Hi all; I searched the Audio Forum for this model and found one thread from 2009. Apparently the OP was able to get the electronics out of the subwoofer cabinet to upgrade components. My question is; how?

The symptom is the power LED no longer lights. The DC power supply is inside the subwoofer, but I cannot see how to remove the PCB or open up the sub without destroying the cabinet.

The speaker set was designed for a PC. It worked fine until I left it unused for a year or so. One speaker contains the volume/on-off knob. The two speakers are powered by the subwoofer thru a DB-9 plug. I've flexed the cables and connections but got no sign of power or sound.

[mmartell]

Re: Logitech X-230 PC subwoofer powerless

Through the removed woofer maybe ?

[Andrew F. Ali]

Re: Logitech X-230 PC subwoofer powerless

Remove the screws on the metal plate at the back of the woofer and you may have to pry the plate-amp a bit to loosen and remove it. The PSU and amplifier is on the plate.

[steves7839]

Re: Logitech X-230 PC subwoofer powerless

... you may have to pry the plate-amp a bit to loosen and remove it. The PSU and amplifier is on the plate.

I can only get one corner of the circuit box out of the case. Some of its' wiring must be secured inside.

[Andrew F. Ali]

Re: Logitech X-230 PC subwoofer powerless

How easy is it to remove the speaker? Most likely it's the speaker wire not long enough. Don't tug on it too hard, though.

[R_J]

Re: Logitech X-230 PC subwoofer powerless

Here is the video, its a pain to remove the grill so try not to bend it out of shape https://www.youtube.com/watch?v=aLoh4jRSgfU

[steves7839]

Re: Logitech X-230 PC subwoofer powerless

Great, thanks for that video link. That should get me moving forward!

[steves7839]

Re: Logitech X-230 PC subwoofer powerless

The issue appears to be with the 110VAC-14.4VDC transformer. It has no electrical continuity through the AC side. To be continued.

[budm]

Re: Logitech X-230 PC subwoofer powerless

May be you can upload good clear pictures for us to look at.

[Andrew F. Ali]

Re: Logitech X-230 PC subwoofer powerless

You seemed to have found the issue with the Subwoofer. Replace the transformer and your system would work again. If you cant get a transformer with a 14.4 V output a a5V output would work. It would be a 2.5A to 3A transformer.

[steves7839]

Re: Logitech X-230 PC subwoofer powerless

I bought a 1A 120VAC-7.5+7.5VAC transformer. I only bought one NTE5801 diode for rectification. With this transformer it appears I will need 4 diodes to create a bridge. I also bought a ECG4926 15.3V zener for protection and a 100uf 100V non-polarized capacitor for filtering. The speaker pcb uses 14.4VDC at 1A.

[Andrew F. Ali]

Re: Logitech X-230 PC subwoofer powerless

I bought a 1A 120VAC-7.5+7.5VAC transformer. I only bought one NTE5801 diode for rectification. With this transformer it appears I will need 4 diodes to create a bridge. I also bought a ECG4926 15.3V zener for protection and a 100uf 100V non-polarized capacitor for filtering. The speaker pcb uses 14.4VDC at 1A.

I think you would need at least a 4700uF 50V Electrolytic capacitor as a filter as that 100uf 100V non-polarized capacitor CANNOT be used as a filter. Instead of 4-diodes to build a bridge why not simply get a bridge rectifier instead?

[budm]

Re: Logitech X-230 PC subwoofer powerless

I bought a 1A 120VAC-7.5+7.5VAC transformer. I only bought one NTE5801 diode for rectification. With this transformer it appears I will need 4 diodes to create a bridge. I also bought a ECG4926 15.3V zener for protection and a 100uf 100V non-polarized capacitor for filtering. The speaker pcb uses 14.4VDC at 1A.

How did you come up with 100uF 100V NP for filter Cap?
You need to show the pictures of the inside the unit.
BTW, something is not right about the label on top of that transformer, it shows O/P 14.4 VDC 1.0A, you better show us more pictures of what we are dealing with.
https://www.badcaps.net/forum/attach...8&d=1545332571

[steves7839]

Re: Logitech X-230 PC subwoofer powerless

something is not right about the label on top of that transformer, it shows O/P 14.4 VDC 1.0A]

True. The only way I can explain the transformer labelling is perhaps the transformer has an internal rectifier or two, which would convert AC to a pulsed "always positive" wave.
My power supply design is purely speculation; I will go with a larger nonpolarized cap as recommended above.

[steves7839]

Re: Logitech X-230 PC subwoofer powerless

After taking a closer look at the PCB, I see a diode bridge next to the fuse, and a 4700uF 25V cap nearby. Looks like the transformer provides AC (despite the stamped output legend) and the PCB takes care of rectification.
I plan to reassemble it on that assumption and see what happens.

[steves7839]

Re: Logitech X-230 PC subwoofer powerless

I supplied AC to the primary of my new 7.5+7.5V output transformer. The secondary was left open. Measured output on the secondary leads was <2VAC. The transformer also got quite hot.
The primary reads `70 ohms. The secondary reads nearly continuity between one tap (red wire) and center tap? (green wire). The two red taps read 6 MegOhms resistance between them. This makes me question the internal connection of the secondary.
Is an open-circuit test even valid or should I load the secondary?

[budm]

Re: Logitech X-230 PC subwoofer powerless

Looking at the picture, did you have the Green wire center tap connected to the red wire? Is that what you did?
"The two red taps read 6 MegOhms resistance between them." The winding has gone open circuit.

[steves7839]

Re: Logitech X-230 PC subwoofer powerless

"The two red taps read 6 MegOhms resistance between them." The winding has gone open circuit.

Correct and confirmed. I marked it defective and exchanged it for a new one. With the new xfmr, the primary taps measure 70 ohms, as I would expect. The secondary taps each measure 9 ohms to the center tap, and 18 ohms across. That's more like it. Unloaded, each tap delivers 10.5 VAC for 21 VAC total.

I connected one secondary winding and the center tap to the PCB and hooked up all the speakers. Voila!

Last decision: Should I run all 21 VAC to the PCB by connecting both secondary windings? I suspect the original transformer, labelled OV 14.4V, provided close to 20VAC as well when working. The power supply filter cap on the PCB is 4700uF 50V so I think it could take it.

[budm]

Re: Logitech X-230 PC subwoofer powerless

So the original transformer only has two wires for the secondary side?

[steves7839]

Re: Logitech X-230 PC subwoofer powerless

So the original transformer only has two wires for the secondary side?

Yes. I am upgrading from a nominal 14.4V AC output transformer to a nominal 15V if I connect the entire secondary. As I noted above, the measured OV under load is 10.5V AC between the center tap and either secondary, so 21V AC total.