Logitech Z906 Power Supply oscillating

[katriik]

Hello everyone,

I'm having some issues with my Z906.
It started with the 3 input leds on a few years ago.
Left the system stored for many months until I decided to take a look and tried to follow a YT comment recommending to replace R79 and R80 with 5.6R 2W resistors.
The system came back to life and was working well until today.

I thought the resistors were at fault again, but this time, after replacing them, the system came back to life, but the sound amplitude is heavily oscillating at around 3 Hz.
It makes any sound being played to "FEel lIKE it IS beINg dISTorTED".

Whenever I place my ear close to the PSU, I can hear a clicking sound that also coincide with the 3 Hz oscillation, and when measuring the 5, 12 and 40 V outputs, none of them are stable and they keep oscillating. The clicking sound becomes more apparent when the system is turned on.

I have the feeling that something is not maintaining the PSU output constant, and I can't tell if it is from the controlling side, or from the output.

The clicking noise is definitively coming around the transformer in the middle, I just can't tell if it is from the 120 V being modulated or if it is from a relay (assuming that the RL components are relays).

Any assistance is appreciated.

[StraidTheRock]

Hi there. I had the three LEDs issue earlier this week, and have tried a few things to resolve it.

The resistors R79 and R80 seem fine, checking them with a multimeter reads 5.8 Ohms each.

I connected the speakers on a different wall socket, that seemed to make little difference.

If powering up the speakers while all 5 satellites are connected, the three LED issue comes back.

If powered up without any satellites, the system starts normally. Connecting the speakers after the system is switched on results in the oscillating behaviour you described.

My subwoofer doesn't make any discernible sound, and I can also hear the ticking noise from the electronics.

Have you had any luck?