Repair ZP120

Be warned once again RE those terribly designed stubborn clips. I saw gruvs post about Bending the pins on the MOSFETs when putting the clips back on. When I reassembled, I didn't use the little condoms Sonos included and just had the clip on the metal of the shottkey diodes (D16005). guess that was shorting the 36V line again. back to fully operational. 

Third time’s a charm!

Well, no joy - but oh so close…

I ran 4 jumpers where those traces should be (there are four total connections from the small power supply area to the riser - all four jumpers were destroyed.  I replaced the dead resistor too.  I also had to bridge the two grounds on the secondary side.  This is all on top of having already replaced some capacitors, and the two mosfets.

It booted up ok, but when I hit play I still get the white/orange cycle.

The difference this time is that the 36V section of the secondary does ramp up to 36V momentarily after I hit play.  Once the yellow comes on it falls back to 15V.

The real surprise (to me) is that there is only 280V on the primary side of the supply instead of the usual 320V.  That tells me that there is either still something wrong there, or there is some kind of power draw on the secondary side that is preventing the primary from reaching 320V.  I disconnected the 15v/8v section of the secondary and tried again -- this time the primary gets to 306V.  I think that this means the primary isn’t generating enough power to drive the load properly… My logic is that if there was a short on the 3.3V rail, I should still get 280V, and if there was a short on the 15v/5v rails then I should get 320V.

I’ll keep looking but honestly I’ve been through this one pretty thoroughly so don’t know what to look for any more.

I have another ZP120 that is now showing similar symptoms (including 280V on the primary) but arrived to its condition via a different route.  That one had a bad transformer primary.  I removed the transformer and found that its winding connections had rusted away.  I was able to get them reconnected, but it was microsurgery and I must have damaged something.  When I reinstalled it, it now boots ok but also goes into the white/yellow cycle when I press play.  I think that the primary winding got shorted and it just isn’t generating enough voltages on the secondaries to make it work.

The other possibility for both of these is that the amp chips are fried.  I probably don’t have much to lose to try replacing those at this point.

Actually… I feel so dumb… I still had my dim bulb in the circuit.  Once I removed it everything worked beautifully!

I fixed all four zp120s that I described 10 days ago: https://en.community.sonos.com/advanced-setups-229000/repair-zp120-17442?postid=16419707 .

This included one with multiple rusted traces, another with a rusted transformer winding, one with two bad schottkys, and one with a bad PWM.  There was other collateral damage too (diodes, caps, etc) but those were the dominant issues on each.

I also tried fixing a wifi/logic card, but was unsuccessful.  I had one card that showed a dead short, and another that had a bad NAND chip.  I moved the NAND chip from the card with the short to the other card, but it wasn’t recognized.  It turned out that the good chip was ‘legacy’ and was a 64MB chip while the other NAND that it was replacing was ‘modern’ and was 128MB.  It gave a message of ‘no NAND found’ in the UART, so I’m pretty sure it just doesn’t recognize the chip.

I looked closer at the boards.  The two boards did have different DRAM and NVRAM (with the ‘modern’ device having twice the capacity of legacy for both DRAM and NVRAM).  However, they did have the same ROM chip (the 512k EN29LV040).  So in addition to moving the NAND chip from the legacy board to the modern one, I moved the ROM chip too.  After this, the logic card booted correctly!

U-Boot 1.1.1(1-16-3-0.9), Build: 0.9

MPC8272 Reset Status: External Soft, External Hard

MPC8272 Clock Configuration
 - Bus-to-Core Mult 3x, VCO Div 4, 60x Bus Freq  16-50 , Core Freq  50-150
 - dfbrg 1, corecnf 0x10, busdf 3, cpmdf 1, plldf 0, pllmf 3
 - vco_out  400000000, scc_clk  100000000, brg_clk   25000000
 - cpu_clk  300000000, cpm_clk  200000000, bus_clk  100000000
 - pci_clk   33333333

CPU:   MPC8272 (HiP7 Rev 14, Mask unknown [immr=0x0d10,k=0x00e1]) at 300 MHz
Board: Sonos Wembley
DRAM:  32 MB
DRAM test
Test complete - 0 errors, error pattern 00000000
Using default environment

In:    serial
Out:   serial
Err:   serial
Net:   FCC2 ETHERNET
Hit any key to stop autoboot:  0
NAND ID is 20:75
32M NAND flash (ST NAND256W3A)
S0 provisionally good, KP=1, G19
S1 provisionally good, KP=4, G18
Boot from partition 1
## Starting application at 0x00400000 ..▒TTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT...........................…
 

It is only recognizing 32MB of DRAM despite the card actually having 64MB, but that’s what I would expect given the ROM and NAND chips came from a legacy device that has only 32MB.

I’m definitely a happy camper, having salvaged a working logic card from two previously dead ones!  here’s a pic of the board after I swapped the NAND chip (but before I swapped the ROM)

Wow, really nice work!

Hi All,

  I wish all of you guys are doing OK. I am the one fixed the broken transformer about 1 year ago.

  I figured I will try more repairs during this lockdown just for fun. I got one SONOS AMP off eBay with power up failure. After opening the AMP, I am shocked to see there is a black burn around the input rectifier. The inducter after is completed blown!

  I managed to fix the inductor and now my Amp is back online in the SONOS AMP. Right after I start playing music, the LED turned from solid white to flashing white and amber! It indicates the AMP is bad.

   I check all my voltages and everything is OK except the 36V stuck at 15V even after play starts. I think something is wrong for the 36V regulator. Any tip to diagnose that part of the circuit? 

  Thanks,

Benbendog   

From the 36 volt test point, you can try to trace backwards.  There are two schottky diodes behind one of those nasty clips towards the back of the board from the 36v point.  The 36 volt and ground pass through an inductor before they reach those diodes. Each 3 pin schottky diode package has two diodes and all four of the diodes are in parallel. Check the diodes. Note that the 36 volts does not come on until you press play, so you can't expect 36 volts all the time.

I have found problems here, as well as these short connector on the riser board. The input to the 36 volt supply passes up on that riser connector are is processed on the riser. There are 8 henpins on the connector but only four signals (they are in pairs for amperage I think). When 36v is needed, that circuit that will pass it down through the riser board back to the main board. 

I am glad that I figured out after reading all the other posts in this thread, it is really helpful: 

   It turned out the burned PCB indeed destroyed one of the traces from the rise card to the 3 pin diode. I could not really visualize it but the meter told the truth. I removed two capacitors and solder a thin blue wire as you can see in the picture. 

  With this fix and as soon as I start playing music, I did get 36V and the white/orange flashing is gone. 

   It is amazing with such bad burn in the inductor that the PCB got a hole underneath it but no other components were damaged including the fuse!

   Thanks again for this informative thread. 

Fantastic - Nice job!