Repair ZP120



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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. 🙂
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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.
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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.
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.
Gruv2ths, thanks for the quick reply.
The CPU GND test point is 0 ohms (shorted) to the RTN36V test point but i notised that i dont have power after the transformer on secondary side See picture attachedthe

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Good idea. I'll try removing the Wi-Fi card tomorrow and see what happens.
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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.
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sotisg69
Hmmm, well that's not good. The 36V is what biases the output section.
So we need the 36V.
Can you check to make sure the CPU GND test point is 0 ohms to the RTN36V test point. If not they need to be shorted together.
The controller for the 36V and the 36V gate drive circuit is on the riser card between the power and logic boards. Near the transformer on the riser board. (the transformer is part of the gate drive for he 36V supply)
That is as good a place as any to start.
Let me look at one I have and will see if I can make a test aid.
Another thought, since the bridge was sitting near the amp maybe that wasn't a "fair" set-up. Even with the amp's antennas disconnected, maybe the amps logic board was picking up enough wi-fi signal from the bridge to start processing the Wi-fi signal and triggering the noise issue. I've packed everything up now. Maybe tomorrow I'll try again with the amp much further away from the bridge. However, even if the logic baord stops processing a Wi-Fi signal and the noise disappears (just a theory), it still leaves me needing a new logic board.

It's all fun though!
Hi Gruv2ths,

I had some fun trying to bridge a 0.1ufd cap across some of the caps on the logic board. It's not a practical thing to do on the small package caps but the principal of the problem-solving action is sound give the noise I'm hearing. Unfortunately my efforts had no impact. I don't think it is cap filtering issue. What I did discover, however, was when I disconnected the three amp antennas from the logic board, and therefore shut down the Sonos net, the noise almost entirely disappeared. The amp was hardwired by Ethernet cable to my music server and the amp had been broadcasting to the other Sonos units. I could still hear the noise faintly but not enough to make the amp unusable which was the case before. Unfortunately I don't want to use the amp as a stand alone amplifier unconnected to a net. I then tried connecting the amp by another Ethernet cable to a Sonos bridge. The Sonos net went into action, but the noise returned which I didn't expect. I thought the Ethernet would just be an in and out connection through the amp with no impact on the noise. In any case, it appears that the issue is in the logic board and not as simple as a damaged cap.

I'm not sure whether I want to sink any more money into the amp at this point.
Hi Gruv2ths.
After i´m push play its still 15V at 36V testpoint?
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Hi Sotisg69,
Well if you’re original problem is gone but now you have a new problem, I would definitely resolder the pins of the new IC. Maybe take a magnifying glass and see if you have good solder flow on each pin, and more importantly make sure you have not bridged and pins with solder.
After that when you push play, make sure your 36V test point on the bottom of the power board goes from 15V to 36V.
If all that is ok, there is a pre-amp chip between the logic board and the power amp ICs. It has a mute pin that you can see if it is stuck. But it’s unlikely. More likely your already on the right track.
Hello gruve2ths excellent jobb back there.
I have a zp120 it goes flashing orange and white when play is pressed. I have changed the driver IC 14pin on the logic card and that broblem was solved internet connection and volume ok but still not get any sound from the speakers!! I'm not sure that i soldered all the pins from the new 14 pin IC on the logic board .... is there any chematic or can i measure it some way.
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Pdog,
You can take a radial leaded ceramic cap and touch its leads to the various ceramic cap leads while the noise is obvious and see if any of them seem to like the parallel capacitance and the noise is damped. Just a thought.
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Pdog,
What I meant was, look for cracked ceramic caps.
I have a spare logic board.
Will message you.
Gruv2ths,

I couldn't detect visually any cracks in the solder joints of caps on the logic board. I don't have the oscilloscope or skill to troubleshoot the noise I'm hearing. I'm an old analog guy and digital control circuits are new to me. I'll wait until I can locate another logic board to try as a replacement. If you or anyone else on the forum has a logic board they want to sell then please let me know.
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I am still puzzled as to why your shorted diodes don't blow the fuse. Wonder if the common core inductor just before the diodes has been blown open?
Good news on your Play5, never tried to fix one. I have a Play3 that shuts down after a few minutes. That I will save for another day.
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Gruv2ths thanks. I get the same so transformer should be fine then. Need to peel back the onion a bit more. Parts have arrived so will start replacing the diodes and capacitors. Also managed to fix one of the Play5 (1st) gen which I bought recently. Just had to replacw the 10 Ohm resistor in the power supply on the primary side.
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Pietje, here is what I measured.
Let me know if it’s confusing
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Pietje Puk - Let me make some measurements on a 36V converter transformer that have here. The continuity should be the same on mine as yours, different turns ratio though I think? (given the lower mains voltage here). If it's the transformer, all is not lost. With the bias converter transformer, when they go open usually once removed you can see where the winding burnt off the termination pin. Fingers crossed that if your transformer has blown open that it can be repaired the same way.

Piperdog - Thanks for the youtube, that helps. Very weird! Wondering if you had a power surge, if maybe some of that over voltage made it through the bias power converter and up to your logic card. If you have a microscope, can you look for cracked ceramic capacitors? I suspect noise that should have been damped is getting in and causing that weirdness.
Pietje, he is using a known good power board so hopefully the Class D stuff is ok.
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Piperdog,

Have you ruled out a problem with the low pass filter (LPF) of the class D amplifier? The noise you hear may be "switching" noise leaking through the LPF...the electrolytic capacitors may need replacing.
Hi Gruv2ths,

I tried both your riser card and mine with no change in the noise level issue. The noise exists whether the analog inputs are used or the source is digital streaming. I posted a video in YouTube. Hopefully you can access it at:

https://www.youtube.com/watch?v=l2rIuxriv_s

I'd like to get my hands on another logic board (i.e. the top board) to see if that would eliminate the noise.
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Gruv2ths, sorry one more question. Do you have the winding diagram for the transformer PQ3230 in the 36V section? I think mine is dead (would explain the broken Schottky diodes). On the primary side I only find one good winding whereas there are 3 pins with wires attached. On the secondary side no connectivity between the thick wires which run into the pcb. Will be tough to find a replacement...maybe need to take it apart and wind a new transformer myself. Thanks!
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Gruv2ths, I measured the 1000uF and have ordered SLPX102M200C4P3 CORNELL DUBILIER - diameter 25mm, height 45mm. Not really high quality but you are right, space is tight on the pcb.
By the way I'm in the city Leiden in the Netherlands. Also have 2x broken Play-5's lying here (1x PSU ticking and 1x amp stages blown up) . Ever done some work on those?
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OK cool, the bulb is worth the work to get running, will be helpful for anything off line you test.
I have had a hell of a time getting those 1000uf caps in the right case sive. A little wider and they are too wide, same goes for the height.
Looking forward to hearing how the parts change works out.
If you don't mind me asking, where are you? I am in Texas.

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