Repair ZP120

Pdog,
Wow this is a new one for me.
A few thoughts.
- I have noticed that when removing the antenna connectors from the wifi card it is exceedingly easy to mess up the termination given all the glue holding them in place.So you might want to try connecting the antennas one at a time and see if one of them makes the problem worse then the others. These things will work without all 3 antennas connected.
- Another thing you can try is to remove the wifi card all together and see what happens. Then just run it with the ethernet, for that test.

Good idea. I'll try removing the Wi-Fi card tomorrow and see what happens.

Gruv2ths,

Bingo! It's the Wi-Fi card. With it removed the "static-like" noise is gone - even with a Sonos bridge (radiating RF) sitting next to the amp.

The Wi-Fi card is tricky to remove from the logic board. There is a mechanical clip on each side of the card and glue has to be removed to free it. There is also a small square foam pad glued between the Wi-Fi board and the logic board to secure the Wi-Fi card even more securely. I mention that should anyone else try to remove the Wi-fi card from the logic board.

The amp is connected to my music server by Ethernet cable and there is a pass through Ethernet connection to my bridge which then creates a Sonos net with my other units. As long as my amp doesn't need W-fi, I'm ok. Everything sounds and works fine. BTW, without the Wi-Fi card in the amp, the front controls on the amp are disabled. Fortunately a remote controller will still perform those functions.

Pdog,
Glad you got down to root cause.
Didn't know about the wifi card disabling the front button panel.
Thanks for the heads up on that.

sotisg69,
FYI-You won't see a voltage on the transformer secondaries unless you are in AC mode with a tru-RMS meter.
And the DC measurements need to be made with the black lead of your meter to either RTN36 or CPU_GND (they are shorted together as you mentioned)
A few observations, if your AMP shows up on your phone then you must have 3.3V, 8V(5V after the liner reg) and 15V. You most likely have your meter referenced to the wrong point.
Another though is that the logic card probably turns on the 36V supply through the driver chip that you replaced. So if you're not sure the solder is correct on that chip, i would concentrate there. Can you take a high res pic of the chip on the board for us to take a look at? We may be able to inspect your solder if the pic is clear enough.

I misled you. I forgot to reconnect the ribbon cable from the front panel controls! It attaches to the logic board directly below the Wi-Fi card. The controls now work fine. Your reply made me rethink what I had done. 🙂

sotisg69
Oh my! Well that's not good.
What I would do is take some isopropyl alcohol with an acid brush and clean away the flux and see what is left. Also Tin the pads that are left once clean.
I will take a pick if a good board. Give me a little time.