Repair ZP120



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A slight update... the choke filter in the upper left corner of that picture (the big one) has 4 wires. I think I have detected a short on it or something connected to it... between the primary and secondary, I get continuity with a resistance of 148 ohms. Could that be that the inductor has a short? Keep in mind it was DMM tested on board and I have not removed it.

The resistor that blows comes off the primary... so there seems to be a relation.
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I pulled the inductor and its good.... so thats not it...
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Great work documenting your troubleshooting and thought process. We will get good at this some day, maybe Sonos will hire us?? LOL JK
So the inductor in the upper left of your picture is the common mode inductor that is in series with the 28V supply.
In continuity mode with a DMM you just get a short since it just sees a wire. I once removed that inductor (it was a real pain getting all 4 wires back in) in an attempt to find out if my short was in the rectifier (2 diode packs clipped to the chassis) or the load. For me it was the load. One of my amp ICs was a short. That is the unit I am working currently. I will share a troubleshooting slide on the 28V supply when I get it working reliably.
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@gruv2ths thanks for jumping in! Yes... removal of that inductor was easy... putting it back wasn't. I had to get creative and solder wire patches to get it through the hole so I could solder the leads back... took quite a while.

The dim light is indeed bright. The TO-220 package (center of my photo on the heat sink) PWM gets warm for sure. I'm guessing the short is somewhere in that area. Just need to get that piece off but I dread it since it has a lot of solder points and the heath sink. I was dreading pulling that component.

Not sure how to test a PWM... I'm guessing that will take a breadboard.

Finding this short is not easy!
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The 2 RTN points on the transformer are showing 0L. I tried to short those too, but got nothing. Actually I am getting no power on the secondary winding (testing 1 and 2 for 3.3V and 3 and for for 8.4 volts, and 3 and 5 for 15v). They show nothing using a 60W bulb. Trying a150W bulb... more or less the same. I get some voltage on the primary (like 10v), but nothing on the secondary.

The PWM is warm so its the likeliest suspect at this stage. The PWM is HOT with the 150W bulb.
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Your assumption seems correct. The PWM is not switching therefore no secondary voltages will show up. I would unsolder that PWM and watch the bulb go out!
If it’s too hard to get the PWM out in one piece, cut the leads and unsolder them one by one.
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I removed the TO-220 PWM - and wouldn't you know... the bulb goes dim. 🙂 The part shows 30 ohms of continuity from pin 1 (GND) to pin 3 (Vcc) and 32 ohms from GND to pin 4 (FB). The continuity is in both directions. Based on the schematic, this part looks blown to me.

I think we may have found the culprit. Now I just need to find a replacement. It is a 5M0265R Fairchild. Looks like the replacement is a KA5M0265R.
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Nobody carries some of these parts in the US, so I need a long wait from China (yes not Mouser or Digikey - seems to be special order). In the mean time I decided to probe around and have a small concern. The datasheet on the KA5M0265R states that the max VCC on this is about 30V. My testing on pin 1 (GND) and pin 3 (VCC) on the Sonos board for where the KA5M0265R goes shows 44V. So I am wondering if that is what may be blowing that? @gruv2ths, when you have a chance, can you post what VCC you get at pins 1 and 3 so I have a comparison?
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I am reading 13V across pins 3 and 1. That is with the dim bulb installed so it is probably a little bit higher.
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Is that with or without the PWM attached? Im wondering with the PWM attached, it may pull some of that voltage down. I am currently waiting on that PWM from China.
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Yes that is with the PWM installed.
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Cool... yeah, mine is with it removed. I'm reading 44V at 1 and 3 with a dim bulb as well. I bought a pack of 10 of the PWMs from China, so I have room in case of failure. I'm really hoping this is the bad component since my bulb is full dim after the caps charges and this PWM is removed. I'll post when I get them and try it out.
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New PWMs and SCK 054 Thermistors finally came in from China. I replaced them and just as I thought, the PWM pulls down the voltage. Checked at 13.03V on pins 1 and 3 on the PWM 😉 Fired up the dim bulb and it went dark. Shut off the power and put the wifi cards back in. Moment of truth... fired it up again with the dim bulb... and the white LED flashed.

Waited a few minutes and opened the iPhone Sonos app. Bob is your Uncle! There it was in all its glory and works!

The Sonos lives and is revived. Total cost for replacement parts: $3.00. Total opportunity cost (I almost tossed it)... $500. Savings to fix it myself: $497.00. Priceless.

I want to personally thank @gruv2ths for the insight on this, and @chicks for the dim bulb ideas. That sent me on a Youtube and reading spree that gave me the tools and confidence to diagnose and fix the problems. Thanks for all the help!
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'Bob is your Uncle!" Greatness.
Happy for you! Congrats!
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Thanks. I would like to share a couple of items that may help others...

I have no idea what kind of solder that Sonos uses, but it is insane. In order to get it to melt, I had to get my Hakko iron up to 900 degrees. 700 (its default) would barely get it to melt. Getting it off components was a chore. That PWM and heat sink took a good 45 minutes to get off along with about 2 feet of desoldering braid. I am surprised I didn't destroy contacts as I really had to put that iron on for a while to get that solder to move. I tried a desoldering pen too, but to no avail. The best way to get it off was keep cracking at it with desoldering braid. I would love to hear if anyone has any hacks or ways to deal with such a problem.

Also, the dim bulb was brilliant. What a great tool to build. It is critical for testing any sort of power supply to keep you from blowing more components. Without this, I would have destroyed multiple resistors and thermistors that kept blowing. I built this for about $25 and you can get the parts at HomeDepot:

https://www.youtube.com/watch?v=rDe6oLKm-ao

This one was nice and clean to make - took about 10 minutes. This helped me trace the hot part. A 60 watt bulb seemed to do the trick for finding the failed component. I tried a 200 watt bulb and it let too much power through, so the bad components would get raging hot quickly. From my readings, the hot part is almost always the culprit for a failed component.

The best resource that I found for fixing and diagnosing power supplied is here:

http://www.electronicrepairguide.com/Smps-repair.html

The guy sells a PDF book that details everything from how to test different components to what tool to use. He has a nice chapter on a dim bulb tester. That site and doc really walks through the different sides of a power supply and what to look for. IMHO, that was invaluable.

Anyways, I really hope this helps others. This was a great learning experience and has given me the confidence to perhaps start hunting for bad Sonos products on eBay and fix em up. ;-)

Final words... I really want to encourage people to post in these forums for help. We CAN fix these things and with a great community like we have here, we can keep these things running. 🙂
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I put together a little procedure for removing the bias converter PWM.
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Awesome stuff! I was able to remove mine w/o removing the caps but it certainly would have been easier w/o them. One tip... the heat sink paste Sonos uses is really cheap stuff. If I didn’t know any better I would think it’s just white lithium grease. If you remove the PWM, clean it and use the arctic silver 5 thermal paste. It will distribute the heat much better.
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Hi All,

I just purchased a CONNECT: AMP from eBay. The auction description says it does not power on and I am hoping to use this thread to troubleshoot and fix it.

@m0untainman and @gruv2ths: Can you tell me where you purchased your part from?

Thanks,
Andy
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Tough question. There is no go-to source. Some of the choices that Sonos has made are exotic, like the integrated PWM they use for the bias converter. They use a non-integrated pwm for the amp power supply, also not available from Mouser and the like. You can always get stuff from China via eBay for example.
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Hi All,

I just purchased a CONNECT: AMP from eBay. The auction description says it does not power on and I am hoping to use this thread to troubleshoot and fix it.

@m0untainman and @gruv2ths: Can you tell me where you purchased your part from?

Thanks,
Andy


First bust it open and find what may be bad. Follow some of the diagnostics in this thread. It can be one or multiple parts. For me it was 3 parts. A dim bulb tester is your friend and without that, expect to blow even more. The fact that it will not turn on is a semi-good thing as its a pretty decent bet its the power supply.

As for parts, you can try Mouser or Digikey. But as gruv2ths said, some of them are exotic parts and difficult to obtain in the US. The 2 places I got mine from are Aliexpress and eBay. They will likely come from China/Hong Kong/Taiwan, and expect a solid 20-30 day wait. They are all obtainable.

Feel free to ask questions here and we can try to help you on your quest to fix this.
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@m0untainman and @gruv2ths: Thank you both. I will be opening the unit when it arrives and will update this thread once I do.

Andy
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Ando, did you get the ZP120 on eBay this weekend that went for $50 ish? If so smokin' deal!
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Ando, did you get the ZP120 on eBay this weekend that went for $50 ish? If so smokin' deal!

No but I saw that one after it ended. That was a good deal! I got a newer CONNECT AMP for $150. Hope it will be an easy fix!
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On your first one getting the chassis apart is an adventure.
If there is no blinking lights, then you prob have a blown fuse and no bias converter.
Listen to m0untainman, he knows what he is talking about. Replace the blown fuse with a 110V light bulb.
Then go looking for trouble.
Have fun!
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Thanks! I just got notice the unit shipped and will be here next week. This weekend I am going to build a dim bulb tester and am planning on following Daniel's blog on disassembling the AMP. I am pretty good with soldering and have already checked out some possible part replacements on eBay.

Edit: I just found a site with some pretty good directions on building the dim bulb tester: http://www.geek-tips.com/2015/11/22/dim-bulb-tester/

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