Repair | Logitech Z906 Burnt Component C86

[egolgeli]

Hi,
In an early morning, I went to my room and felt the known burnt circuit board smell. Seconds after, I found my Z906 dead. It never turns on since that moment. When plugged to AC, there is a clicking sound but nothing appears on the controller unit. Power button is totally unresponsive.

I checked the board and found a large burnt mark around the component C86. While cleaning, burnt component (C86) dropped. Also, components on the other side of the board, C49, R72 might be affected as well, but there is no visual damage there.

Anyone encountered such/same? Any known or suggested way to fix this? Is it possible to buy the power unit somewhere?
Thanks,

[MathWizard]

IDK the Z906 but it looks like the secondary side of a SwitchModePowerSupply-SMPS, those 2 big thing's would be 2, dual diodes. They don't really look burned, but they need testing.

Assuming the problem started and ended about there on the secondary side rectifier's, and no chips got damaged, then yeah it should be pretty fixable with common parts.

Like for instance, if one of the caps on the secondary side failed and shorts say the 5 or 12V to the local GND, there will be sensing circuits and chips that will see this problem of low voltage, and quickly tell the primary side chips to shut down. If the diodes failed as a short/low-resistance, then some over-current or over-voltage sensing should shut down the PSU.

If you have a DMM, and a soldering iron, and flux, I'd remove the brunt parts, and check those diodes, and see what the output resistance measured then. It still can be pretty low on some SMPS's, like on a computer PSU, it might measure 100ohms from 12V to GND, on the Z906 it's probably higher.

I haven't fixed that many SMPS, but usually the damage was pretty limited, and the protection circuits did their job and reset or shut down the PSU.


The clicking you keep hearing is probably the PSU resetting over and over as it senses the problem, and resets. With any luck the primary side was fine and still is fine, but you never know, read or ask about some safety questions if you're not sure.