Repair ZP120

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While I am trying to get the transformer out, I found it a bit loose from the frame so the disconnect could be due to mechnical damage. I will find out after it is removed.

I figured to grab my other broken Sonos amp from storage and I didn’t notice it when I bought it but it looks like the previous owner already opened id.

The fuse was open, and the solder points looks very shady, so either he replaced the fuse or only tried doing so.

I had a pair of fuses lying around so I quickly replaced it, reassembled everything and once I plugged in the power chord my lights went out and I could smell electronic burn 🙂 xD 

Is this a case where it’s appropriate to use a bulb? A friend of mine told me to hook up a bench power supply (with very low voltage) and trace the signal from there.

All other components looked good, from the look of it.

BTW How can I figure out that the 110v/230v switch is ok and not shorted?

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Hi Guys,
Wow this is timely for me as I just t-shoot a power board on a ZP-120 with water damage. Man that board was like a bad dream. I had for my first time ever, a transformer winding open sort of like you describe. What i found was he following:
- Check the 10 ohm resistor showing through the hole just to the left of VPRI. Yours is OK if you see 300ish Volts on pin 5 of the transformer primary. This resistor is in series with the transformer primary and blows a lot.
- I also had a trace blown open at the pin 5 through hole. No power to the primary at all.
- Most importantly I did not see any resistance between pin 5 and pin 3. Primary open. I removed the transformer and found under my microscope that pin 3 was blown open to its winding termination pin. There was just a 1/8th inch of wire peaking out of the windings. It is magnetic wire so what you do is put a blob of solder on your solder iron tip and let the wire sit in molten solder until the insulation melts off. Then just soldered a wire from the little piece of magnetic wire to the pin at the bobbin base.
-Same transformer secondary side, if you wee 3.3v but not 8.5 nor 13 you likely have an open where the 2 secondaries short in the PWB, take a small piece of wire and short them back together. I see this fail on 90% of the Amps i fix.
Lots if simultaneous fails on my board, worst onion ever.. Felt good to see all 3 voltages on the secondary.

If your winding is blown open in the windings, then fixing that transformer is way beyond my help.
I can however sell you a used but guaranteed working transformer.

Let em know what you want to do.

I have had a few repairs lately where I have fixed the power board but can't resurrect the logic board. I intend to put a few working power boards with or with out the chassis on sale on eBay.
Please let me know if there is any interest in tis as well.

I really like this forum thread!
Userlevel 1
Hi gruv2ths,

Thanks a lot for the reply and I feel so good someone speak the same language and understand my frustrations. :)

The ZP120 I got had pretty bad mechanical damaged (may have been dropped multiple times, one of the wireless antenna wires was missing), but it has no sign of electrical damage upon close inspection which is a good sign. I trace through the circuit and the 10ohm big resistor is fine and I AM getting ~340V DC voltage on primary pin5. I got very low and stable ~1.5V on both pin3 and pin4 which should be oscillating to generate the current flow for the secondary coils. Then I confirmed I have open from 4 to 5, but ~1.4ohm from 3 to 4. My conclusion is the coil is broken between 4 to 5 more than likely due to shocks that the transformer moved which stretch the coil connections inside. All my secondary coil resistors values are good but without primary...

I am in the middle of removing the transformer, it is not an easy job 😞. My company has state of art rework equipment and technicians but not at my home. 🙂 Please share your tricks on de-soldering. I didn't want to use a hot gun yet.

I am certainly interested in getting your used transformer since I am not sure if mine is repairable. Please send me an e-mail to: for the price info.

I recently just repaired a ZP90 and I was lucky that it was just a blown rectifier diode. Now it is singling in my home office with a dedicated Amp. I want this ZP120 to replace it so I can have the ZP90 for my hifi system. I will have Ethernet connection so wifi is not a must for me.
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Hey man,
Yes your frustration is defiant understood by myself and M0untainman.
So to unsolder the transformer leads takes patients. Lol
I do it in 3 steps.
1) wick out as much Sonos solder as you possibly can.
2) Now flow in as much of your solder back into each hole. This will help transfer heat to the stubborn Sonos solder that is left.
3) wick it all out.
4) on the still stuck pins I get with the iron and wiggle with a tweezer as you remove the heat. This will hopefully keep the solder from cooling back on the pins.
Userlevel 1
Hi gruv2ths,

I managed to get the transformer out but I did a horrible job that I broke off a few PCB pads (should not be a bit deal since worst case I can use wires to connect them back). On the primary side, there are total 8 wires coming out of the transformer that I lost the ordering after taking them out. I took a few pictures to show what I have. Can you take the same from your working one?

I probably will need to get a working one from you anyway.

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Dude! One word comes to mind.... Butcher!! Lol jk
We all had to learn sometime.
I will say that I am concerned about the damage to the pcb. The reason is the high voltage on the primary side. They can midigate creapage and arching in the pcb, but with jumpers all bets are off. So let’s hope we can clean that up, without any fireworks. Dim bulb will be helpful I terms of delivering current to a short. But then again with those huge storage caps across the 300 volts, definitely tread lightly.
I think I know of the unit you are working on. Was it recently on eBay? $100ish no bottom. (Well the bottom mounting chunks were still there) yes if you look closely in the eBay pic you can see the ripped off WiFi connector. I thought long and hard about talking a risk in that one.
I have a bottom and the WiFi antenna for you if you need it. I can give you a package price with the transformer if you like?

Will send the transformer pic later this afternoon.