The amp has no power. Is there an internal fuse for this unit?
Has anyone taken one apart?
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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?
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.
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.
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.
Has anyone taken one apart?
The first one:
Just the input bridge rectifier has a shorted diode that blew the fuse. Once the bridge was replaced it has worked fine.
SOmetimes it came up no led, totally dead, other times it came up and would get 1/2 way through setup before crashing my network.
Noticed a primary side 350V 33uF electrolytic cap was toast. Replaced It and nothing really changed.
This one was a real head scratcher. The blown cap belonged to what appeared to be power converter circuit that provides biases around the board. Noticed that the GND test point had no continuity to the outputs of the tapped winding. I probed a good working ZP120 and found that all of the outputs of the bias converter were grounded together. So I shorted the return of the tapped winding(8.5V and 15V outputs) to the return of the single winding (3.3V output). Was nervious to power it back up, so just in case i used the dim bulb and it worked great. Replaced the dimbulb with the fuse and I am in business.
I did a chart so my crappy memory will have some help next time i tange with a ZP100. See below.
For your Information:
Sonos products are not designed to be opened and repaired out in the world, and we do not provide any resources or replacement components for doing this. The warranty services for Sonos components also does not cover units that have been opened in any way.
Even if your player is outside the standard warranty time, we can probably still assist with a replacement as long as it hasn't been opened. There will likely be a fee for the replacement if it's out of warranty.
Anytime a unit fails, we want them to come back to us when possible so that we can review what happened and make adjustments if there's need.
I tested the rectifier on the input side (the one clamped to the chassis) and it looks good. I tested the diodes and those look fine. All caps are looking good too. The fuse is fine... it never blew.
I am guessing the problem lies downstream from the components listed above. A couple of questions...
1 - That TO-220 you mentioned... is that the one that has a heatsink screwed into it and standing up? Do you know the code on it or type as I cannot tell.
2 - What is the secondary rectifier your are referring to? I would like to test mine to see if its checking out (or not).
If you have any recommendations, I would love to know how to any techniques are parts I should be checking on the PS board... I am thinking this is simple... but I am having a tough time narrowing it down.
So I decided to fire it up under the dim bulb tester after replacing the 10 ohm resistor and putting back the thermistor... and the light bulb shined brightly so I still have a short somewhere....
I cut the power and decided to test for heat. Again, that resistor was getting hot (and was saved due to the dim bulb tester).
Here is the resistor and it is hot (notice the circle labeled hot):
Anyone have ideas on how to hunt down the short?