Repair ZP120



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The amp has no power. Is there an internal fuse for this unit?

Has anyone taken one apart?
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I repaired the one I am using. It was a no power failure as well. It appeared to have some sort of liquid damage on the logic board that shorted an output of the power supply. I fixed that damage on the logic board, then started looking through the power supply. What I found was a TO-220 (or similar) package dual schottky rectifier was now shorted, also the main bridge rectifier on the front end of the power supply was also a short. Once replacing those 2, the dim-bulb went bright then dim and the indicator started flashing. And I friends was in business!
I liked the ZP120 described above so much that I just bought another ZP120 with the same fail description. I crack it open tonight. Will update this forum when I get it working.
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No updates. Keep us posted on your repair efforts.
Any new updates? I just bought a dead ZP120 on eBay and will be diving into it next week.
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I don't have any updates. I put my repair on hold until I can find someone who has had more time than me and who has created a schematic of at least the power supply section. Alternatively I'm keeping my eyes open for an inexpensive used ZP120 so that I can use it as a reference for the correct voltages and therefore to trouble shoot my nonworking unit..
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Piperdog, Any chance you've got any updates? I'm in the same situation.
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I decided to skip the dim bulb tester although I'll keep it in mind for the future. I replaced the 2 thermistors, 2 varistors and 5A fuse in the power supply section and applied power. The good news is nothing shorted out. The bad news is that some component must be open downstream because I'm not getting voltages where I should. I wish I had a schematic. It would be so easy now to trouble shoot with it. Or another good unit to compare voltages.
Google Dim Bulb Tester for a simple, low cost way to protect devices that may still have issues...
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I didn't realize that it would be that inexpensive for Sonos to repair an out of warranty unit. Thanks for the info. Unfortunately they may not touch my unit now that I've opened it up. At any rate, I received replacement fuses, varistors and thermistors today from Digikey. If things work out I'll post the Digikey part numbers. Now I have to find time to install them. Hopefully they are all that is required but of course there is a reasonable chance that something else is wrong with the power supply causing these parts to fail. I'll know soon.
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You could have sent it in for replacement for a modest cost. I sent back a ZP100 for around $150. SONOS sent me back a brand new ZP120.
piperdog,

Be sure to purchase at least two of these thermistors because the first will likely blow again as soon a you apply power. I suggest that you track down the root cause before applying power again. This is not a hard as it seems, just follow the current that blew up the original thermistor. This will lead you to a really sick component. Be sure to replace everything in that current path.

Also, I am leery about running up the power voltage as a strategy to troubleshoot switch mode power supplies. When the voltage is much lower than expected, the switch mode stuff will really try hard to maintain the specified output. This could imply much more current than average use cases.

If you have lab power supplies available, separate the ZP120 into modules, power them up and test them separately. The lab supply will have current limit capabilities to protect itself and the device under test from unreasonable current levels.
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Upon closer examination I see that a current limiting in-rush thermistor has over heated and cracked. Its a SCk054 (schematic TH16001) which I'll have to replace to progress further.
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Lacking a schematic to do proper trouble shooting I slowly applied power to force evidence of a fault without hopefully doing damage. One of the varisters eventually exploded. I desoldered its remains. Although I had measured it as open it was evidently damaged and shorted out under power. I reassembled the unit but still don't have power so I'll look for another faulty component on the power board. At least now I can apply full power without any shorting occurring.
piperdog,

A flash of light usually indicates something has died -- in a hurry -- usually letting out its smoke. Of course, everyone knows that smoke is required for proper operation and after the smoke leaks out, operation ceases. Further, the flash of light (former) device is usually the victim of another issue.

Some units will blow fuses for no good reason other than the fuse was probably poorly specified and fatigues over time, eventually failing. I don't have enough data to know if ZP120 is one of these units or not.

I can't recommend the strategy of inserting a fuse eliminator as an expedient. Unless I know that a given (dead) unit is subject to nuisance fuse failures, I'll track down the root cause of the failure before applying power to a unit. Powering a (dead) unit prior to repairing the root cause typically expands the failure, fuse or not. Also, even if they appear to be OK, replace any components in the current path of the root failure because these components were probably stressed during the original failure and you will likely be faced with another similar failure as these stressed components fail in the future.

Inspect the board using a magnifying glass. There is almost always some sort of visual physical clue indicating which component gave out its smoke. Of course, with our modern, ever shrinking components, these physical clues can be small too. Sometimes the only clue is a small black dot on the non visible side of a surface mount component.
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I bought a used Z120 with an unidentified power issue. It was dead.

The 5A fuse is open. No other components show visible damage. When I shorted out the fuse to see if the amp would power up there was a momentary flash of light near the centre of the power board. I say momentary because I quickly opened up the fuse again.

It appears to me as if something arced or there is a short somewhere downstream of the fuse. Everything I measure with an ohm meter seems to react ok. The varistors near the large filtering caps are not shorted. Before I try to replicate the action of shorting the fuse again to see what is arcing I thought I'd see if anyone had any ideas as to the fault.

Also, has anyone created a schematic of the power supply?
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This guide might help although it is for the ZP100.

http://www.mediafire.com/download/0duavcuf1zyuc8u/sonos_dismantle.pdf
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I too am keen to work out where the fuse is. I tried here and here but not much joy. Anyone got better info? B.

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