Help needed in repairing Sonos Connect - ZP90 (power board) after power surge

Thread Starter

hafren

Joined Mar 1, 2019
28
I am very much a novice in electronic repair but am keen to learn but I’ve drawn a blank in fixing my Sonos connect so looking for help. After removing the power board I could tell the fuse had blown and a NTC thermistor had failed. I also suspected capacitor C206 (1800uF, 6.3V) which appeared to have bulged top. I do not see any other signs of distress so I replaced all of these components and upon power up the fuse immediately blew.

So there is clearly something wrong/shorted downstream of the earlier failed parts thermistor & fuse and need some advice what I can check. I have searched unsuccessfully to find schematics but have read many other posters that have successfully repaired their Sonos connect after a power surge. Most others were successful in replacing the exact same components I’ve replaced so what I can check next? Pictures of my power board are attached.
 

Attachments

narkeleptk

Joined Mar 11, 2019
480
Hard to see much from photos and I do not know power supplys well but you could check that so-8 IC there for a short and check those diodes. If they are ok its probably the transformer. Maybe one of the guys who know power supplys will chime in and lead you a little better.
 
Last edited:

Dodgydave

Joined Jun 22, 2012
9,912
It's a switchmode psu, and it's probably blown the chip (pins 1, 2 shorted) fuse, thermistor, on the output is just a diode, capacitor and opto-coupler and TL431 zener for regulation.

This is the chip and a typical circuit diagram...2cx86zd.png
 
Last edited:

Thread Starter

hafren

Joined Mar 1, 2019
28
It's a switchmode psu, and it's probably blown the chip (pins 1, 2 shorted)
I checked the chip, Fairchild 5M0165R, for shorts across pins; 1/6/7/8 (drain) to 2 (GND) & is open circuit. I looks difficult but not impossible to desolder from board but if its open circuit does that indicate its not the problem source? I'm going to make a dim bulb tester to see if I can run the circuit without blowing the fuse and see if I can detect any components getting hot? Any other advise on what I can do/check?
 

Dodgydave

Joined Jun 22, 2012
9,912
All i can suggest is replace the mosfet, chip, and check any other silicon parts D2, looks like you have removed a few ...
 
Last edited:

LesJones

Joined Jan 8, 2017
2,972
The bridge rectifier is also another possible cause for blowing fuses. Check that none of the 4 diodes in the bridge rectifier are shorted.

Les.
 

Ylli

Joined Nov 13, 2015
1,020
Need to be careful using a DBT or other limiter or soft start when testing a SMPS. One of the features of a SMPS is that if the input voltage is low, it will just draw more current to supply the needed output. It is effectively a negative resistance. As such it can be made to oscillate quite easily if you try to moderate the input current/voltage.
 

WAHanley

Joined Dec 24, 2019
1
I appreciate all the prior posts as I was quite disappointed when my Sonos failed a few months ago.
When I cracked it open and measured the voltage it was clearly due to a failed power board.

Initially I was going to attempt to rework the power board but was finding it difficult identifying and locating the original board components. Fortunately, I was able to locate two small form-factor AC to DC power supplies for ~ $9 a piece. I carefully soldering them in and am happy to report that my Sonos lives again!

Along the way, I took a couple of photos to document the process and just added some rework instructions to the attached PDF file. If you are reasonable confident with a soldering iron and NOT ham-fisted it should be a breeze.
 

Attachments

Top