Repair ZP120


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

Has anyone taken one apart?

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Got it to play music yesterday. Sounded great after such a journey.

One thing, it was not very consistent. On high volumes, it sounded great but down low there was some cracking. 

Booting it up today, I only get a slow flashing orange LED and sometime a very dim white light. I am getting 15V on the 36 pad and 36V when I play some music through the app. That all works fine.

I started digging deeper (on the secondary side only, assuming the primary works perfect) and found that on only one of the two shottky diodes, the middle pin is getting 15/36V. The most outer one (diode, not pin)  is getting voltage while the more inner one is not getting anything. What are these middle pins connected to? As I do not find an immediate link probing my DMM. The two outer pins are ground I assumed.

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Couldn’t agree more! Never suspected the riser and main board to be faulty as the power supply gave me most troubles. 

There were two small spiders/bugs stuck inside the shielded compartment of the main board. They must have caused a small short preventing the amp form booting as all the voltages were there. 

A very close visual inspection often saves many hours of troubleshooting.

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Bob’s my uncle! Got it working, you will never believe what the problem was.

There were two small spiders/bugs stuck inside the shielded compartment of the main board. They must have caused a small short preventing the amp form booting as all the voltages were there. Got it set up in the app right now. The amp is connected to WiFi and is now slowly blinking orange. I guess that is because I have not selected anything for it to play. Will test the sound soon. Now the challenge of putting everything back in the case. Very happy with my progress so far as I learned so much with this amp. I was a total newby before. Thanks for the help to whoever was involved in this forum.

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I replaced the mosfets and now I am having the bias voltages. The 3.3V and 5V is correct, but the normally 15V shows up as 13.5V on my board. Still no status light and there is a ticking sound on startup which repeats about 6 times with an interval of about a second. I am out of options at this moment. It seems like the voltages coming out of the transformer might be a bit lower than usual? The 3.3v and 5V might be correct due to the regulator, but the 15V is not there as I think it comes straight from the transformer. Also the 5V_sw pad shows about 0.2 volts.

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As I cannot find a retailer selling the K13A60D, I am looking for an equivalent n-channel mosfet. I came across this one ;NTP360N80S3Z. The only main difference is the avalanche current, which is 2A instead of the 13A of the K13A60D. Would this matter? My guess is yes, but I would like another opinion by more specialized people in this forum. Also the turn-on/off times differ a little. They all seem to be shorter on the equivalent mosfet.

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Allright, thanks for the clarification! Sorry for my lack of terminology, I have never gotten any electronics classes but I am quite up to speed through what I learned myself. I never got the device to play music. In the state it’s now, the dim light bulb goes out but no white light and no bias voltages nor any voltages on the secondary side, so I suppose the PWM is not switching. What do the transistors (K13A60D) do in the circuit? As these heat up quickly. 

The PWM is good for sure as I just replaced it again. Before, the light bulb would stay on full brightness, after replacing the PWM the light goes out after a second. I suppose i will take more measurements according to previous posts in this forum and lead my way back to the problem.

One more thing: I replaced the transistors with a part labeled MBRF 10L100CT, is this similar enough to the K13A60D? I ordered these a while back when I had even less of an idea of what I was doing with this amp 😉 -Edit: Wait, I think these are just two different components. I probably messed up while ordering back then.

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Hi! I found some time to work on this project again. I had a blown 10 ohm resistor and a bad PWM, switched both and blew again. I saw some black marks on one of the yellow caps between the two big caps and replaced those with a new PWM and now the light bulb goes out. Yay. Still no white light though. I did not measure anything on the measure points on the secondary side though. Also these 2 transistors were getting quite hot (but I suppose that’s due to the missing heat shield, case)

I think these are for the 36v which should not be on at that time? -Edit: I now noticed that the other diodes are for the 36v rail- I replaced these 4 diodes (2 pairs that are using case as heat shield). Rectifier is also good, amps don’t seem to be shorted. My only thought at this moment is the feedback unit. Do these even go bad? I would love to hear some thoughts. I will do further testing as I did not measure too much because noticed the diodes getting hot. 

I wonder if you’ve misidentified some components.

The two “yellow caps” located between the big capacitors are not actually capacitors.  They are varistors (or MOV for metal oxide varistor).  These have high resistance, but as voltage rises their resistance drops.  In the event of a voltage spike, these shunt excess voltage away from the circuit, acting as protection devices.  If they are dead then it is very possible your device suffered a voltage surge.  If so then this is recoverable, but there may be multiple component failures.

You said that you replaced 2 pairs of transistors.  The first pair are transistors and you need matching components (part number K13A60D).  The second pair are not transistors - they are dual diodes (part number SBR10100).

When you say it ‘blew again’, how fast was that?  Was it right away, or only after trying to play some music?

The first two transistors you mention are part of the 36V circuit.  When the device is idle (or even playing at very low volume), the amplifier is run off of a 14V supply that comes from the central transformer (which is driven by the PWM).  Once the volume is turned up, then the 36V circuit comes on.  That is where these two transistors come into play.  They are switched via signals that come from the mainboard, through the riser board, then out the small plug in connector on the end of the riser board.  Since this is part of the 36V circuit, you should be able to get the device working (albeit perhaps without any audio being produced), even if these are damaged.

You need to know if the PWM and transistors are actually working or not.  If you use a multimeter in diode test mode, you can look between each pair of pins (eg 1-2/1-3/2-3/2-1/3-1/3-2).  You need to test all pin combinations in both directions.  You want to see either an open circuit, or a small voltage like 0.6V.  If you get any shorts then the device is bad.

Ideally, if you can get it running with the dim bulb, then you can check the back side for the various bias voltages.  There are test points marked for GND, 5V, 3.3V, 14V, and GND36/36V (the 36V points may measure 15V and that’s ok).  You don’t need the riser board or main board connected to test these voltages.

 

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Hi! I found some time to work on this project again. I had a blown 10 ohm resistor and a bad PWM, switched both and blew again. I saw some black marks on one of the yellow caps between the two big caps and replaced those with a new PWM and now the light bulb goes out. Yay. Still no white light though. I did not measure anything on the measure points on the secondary side though. Also these 2 transistors were getting quite hot (but I suppose that’s due to the missing heat shield, case).

I think these are for the 36v which should not be on at that time? -Edit: I now noticed that the other diodes are for the 36v rail- I replaced these 4 diodes (2 pairs that are using case as heat shield). Rectifier is also good, amps don’t seem to be shorted. My only thought at this moment is the feedback unit. Do these even go bad? I would love to hear some thoughts. I will do further testing as I did not measure too much because noticed the diodes getting hot. 

Thank you! Yes, most likely it is really 2k.

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That looks like it is labelled “31B”.  EIA-96 says that’s a 2.05k resistor: https://www.hobby-hour.com/electronics/eia96-smd-resistors.php

I measured in circuit, and got 1k.  Perhaps it is in parallel with the one next to it.

Сould you please tell me the value and marking of the resistor R16021?

 

I replaced the fuse, replaced the TVR14241 (mov) and i noticed that the TH16001 also cracked. I could not source the Sck054 needed to replace this part in my local electronics store, so I hardwired it for now, and everything works perfectly.

 

If you cannot easily source a SCK054, there are similar devices available, eg:

  1.  SCK054 Specs:
    Zero power resistance at 25 deg C = 5 ohm
    Max steady current at 25 deg C = 4 Amp
    Approx resistance at 25 deg C = 0.18 ohm
    Thermal dissipation constant = 17
    Thermal time constant = 33 sec
     
  2. TDK B57235S0509M0 (RS Part number 467-614)
    ​​​​​​​Zero power resistance at 25 deg C = 5 Ohm
    Max steady current at 25 deg C = 4.2A
    Approx resistance at 25 deg C = 0.11 ohm
    Thermal dissipation constant = 9
    Thermal time constant = 60
     
  3. Yageo NTD04-005M (Element14 order code 3770791)
    ​​​​​​​Zero power resistance at 25 deg C = 5 ohm
    Max steady current at 25 deg C = 4 Amp
    Approx resistance at 25 deg C = 0.182 ohm
    Thermal dissipation constant = 9
    Thermal time constant = 48 sec
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Update: removed almost all diodes from underside op primary side. Theyre all Good. Something I noticed is that all the 5 points of this winding in the secondary side are shorted together, is this right? 

 

The secondary winding has two separate coils.  The first is across three pins with a centre tap.  Within each coil (the first 3, or the second two pins), you should measure a very tiny resistance (under 1 ohm) between the pins -- this is normal for a transformer.  The short between the two coils is not normal.  You may have a short between the two secondary coils, or it could be ‘downstream’ of that.

I’ve fixed dozens of these devices and haven’t seen this particular problem before.  You can try to remove the transformer and see if the dim bulb stays bright.  If it does then the transformer is probably not the problem.  Be warned though… Getting that transformer out and then re-installed is a pain to do.

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Hello, im from Germany and need your Help.

These two capacitors are defective. do you know the data for these?

TH16001 and TH16002.

 

Thank You

Max

Hi guys, I own a connect amp that was plugged (by previous owner) in to 220v when switch was on 110 v.

I replaced the fuse, replaced the TVR14241 (mov) and i noticed that the TH16001 also cracked. I could not source the Sck054 needed to replace this part in my local electronics store, so I hardwired it for now, and everything works perfectly. 

Questions are:

- with normal use (no power surge, no wrong voltage), will the unit get damaged if I keep it like that? 

- is th16001 used in 220v setup, or is it for 110v only, and th16002 for 220v?

 

If it will Increase the lifespan of the unit, i will order the SCk054 online.

 

Thanks for this super interesting group discussion, got me already quite far!

The thermistors here are NTC (negative temperature co-efficient).  These will have a higher resistance when cold than once they warm up.  I’m not an expert but I think that the purpose is to limit the inrush current when the device is first plugged in.  These are used in most sonos devices that drive speakers.  Each of these has large capacitors that charge up, and which will draw large amounts of current quickly without the thermistors.  You may notice your lights dim a bit when you plug in a device without them.  I notice this dimming with the ZP120 Connect:AMP devices, and that’s with the thermistors working!

The thermistors are active in both 110v and 220v devices.

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Update: removed almost all diodes from underside op primary side. Theyre all Good. Something I noticed is that all the 5 points of this winding in the secondary side are shorted together, is this right? 

 

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I have noticed that the 4 diodes (marked with black stripe) do not give any Reading on my multimeter.

 

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thanks! I found a short on the mosfet side, but to be sure, I also want to replace the schottky diodes on the other side… Do you have any idea on what replacement part to order for these? 

If you are referring to the pair of TO220 Schottkys mounted to the case, those are 10 Amp 100 Volt.  Part number SBR1010CT

 

the short I mentioned was not correctly diagnosed. So No short is detected on the mosfet side. Schottky diodes also seemed ok after removing them.
 

I build a dim light bulb tester, replaced the 10 ohm resistor, and removed the MOSFET’s and schottky diodes. When plugging the device in, the bulb goes full brightness. I am using a 53W bulb. Also plugged it in With the input/network card removed. Lamp still goes on… Owner told me the damage was probably caused by water as the amp was placed under a bathtub… Any thoughs? Not sure If the PWM is still ok But as I replaced it last month, it should be.

Hello, im from Germany and need your Help.

These two capacitors are defective. do you know the data for these?

TH16001 and TH16002.

 

Thank You

Max

Hi guys, I own a connect amp that was plugged (by previous owner) in to 220v when switch was on 110 v.

I replaced the fuse, replaced the TVR14241 (mov) and i noticed that the TH16001 also cracked. I could not source the Sck054 needed to replace this part in my local electronics store, so I hardwired it for now, and everything works perfectly. 

Questions are:

- with normal use (no power surge, no wrong voltage), will the unit get damaged if I keep it like that? 

- is th16001 used in 220v setup, or is it for 110v only, and th16002 for 220v?

 

If it will Increase the lifespan of the unit, i will order the SCk054 online.

 

Thanks for this super interesting group discussion, got me already quite far!

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thanks! I found a short on the mosfet side, but to be sure, I also want to replace the schottky diodes on the other side… Do you have any idea on what replacement part to order for these? 

If you are referring to the pair of TO220 Schottkys mounted to the case, those are 10 Amp 100 Volt.  Part number SBR1010CT

 

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I'm sorry, but I'm going to be stupid trying to find a suitable spare part.Can someone give me a link to a suitable spare part, e.g. at mouser or digikey?Many Thanks

Either of these will work (both are in stock as of now)

Mouser #: 527-RL4504-3.2859S54

Mouser # 954-5D2-10LD

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readings at the pins. I thought I could not test this because when I power on the device it blows up. I 

I have an educated guess about what is wrong with your device.  If you replaced the PWM and it still doesn’t work, then I’d check the two mosfet devices identified in these images.  Look for a short between the various pairs of pins (you should not find any 0V drops if you test the 6 combinations with a diode tester).  If you don’t have a diode tester, you can just remove the 2 components and see if the device boots up. 

These devices are part of the circuit that is used to generate 36V power that is used to drive the amplifier.  It is only active when the device is actually playing music.  An otherwise working device will boot up without them, and will even play at very low volume.  After booting up without the 36V present, you won’t be able to turn up the volume, and the device will start flashing amber.  This isn’t permanent and it will go away once you replace the mosfets.

When the time comes, be aware that the silver clip on the top can be a pain to replace.  It can be bent open with two sets of pliers so that it is just a bit narrower than the diodes it covers.  That will let it do its job and it will be much easier to replace.

 

thanks! I found a short on the mosfet side, but to be sure, I also want to replace the schottky diodes on the other side… Do you have any idea on what replacement part to order for these? 

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I'm sorry, but I'm going to be stupid trying to find a suitable spare part.Can someone give me a link to a suitable spare part, e.g. at mouser or digikey?Many Thanks
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But sure… if you can find an SCK-053 (another manufacturer perhaps), then that would work.  I think you want the first two digits >=5 and the last digit 3 or higher.

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Do you mean a SCK-054 or a SCK-053 with 4A? Anwalt,here in germany, I don't find anyone,  who sells one of them. 

I meant SCK-083.  Here is a datasheet for the series… https://datasheetspdf.com/pdf-file/924750/Microtherm/SCK-054/1.  Looks like an SCK-103 will work too.

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