Can not start the board again

[peterhu]

After I connected the computer to Vivado to burn the code, the circuit board was running. I used the dac module to generate a voltage, and tried to use the adc module to receive the voltage and process it. When I detected the vcc end of the JB pin, the circuit board made a 'click' sound. , then the circuit board automatically returns to the flashing state of LED0 and LED1 during restart, and goes out after a short time. At this time, the switch is still in the start state. Then I restart the computer and all the indicator lights will not light up, and the computer will not be able to detect the board. I detected that the power supply terminal has a 12v input, and the vcc at the LED0 and LED1 terminals has a 5v input. There is no voltage on the three ports of the fan, and the chip under the fan generates heat during startup.

[JColvin]

Hi @peterhu,

You mentioned that measured the Vcc end of the JB pin. Could you describe a bit more of what you mean by this?

Do you mean that you had an SMA cable connected to the Zmod Scope and then somehow measured a Vcc on the underside of the board with one of the clips? Or something different?

What gain setting were you using when you were testing the Eclypse Z7?

Thanks,
JColvin

[peterhu]

Hi @JColvin ，

After my test of the pin's voltage,I think the problem comes from the Power Regulation ciucuit.How could I know the correct type of the chip?I noticed from the board that it is TPS65400,but I couldn't figure out its specific type.

 

[JColvin]

Hi @peterhu,

Could you let know in better detail about how you were using your Eclypse Z7 when it got damaged? The design engineer suspects in this situation that the regulator might be fine and that it is different ICs that have been damaged, but we'll need some more information to help better troubleshoot this.

Could you also let me know what test points you measured to determine the regulator was damaged (this post, https://forum.digilent.com/topic/25689-rma-request/, has reference list of useful capacitors to measure).

Thanks,
JColvin

 

[peterhu]

Hi @JColvin ，

I afraid the problem may comes from the short circuit between JB's VCC and GND pin ,when I tested the JB's VCC pin,maybe I accidently contacted to GND pin as well. Now I have tested several pins.When the power is on,the PWRCTL3V3 is 3.3V, while all the VCC3V3 comes out as 0.43V.Also the VCC1V8 turns out as 0V,and the VIN is about 12V.Then I tested VCC5V0 and VCC1V0,they are correct. Then I tested JA and JB's pins,both the VCC3V3 is 0.43V,GND is 0V,while other pins are about 2.08V(JA1-10,JB1-10).Do I need to test other pins?

[JColvin]

Hi @peterhu,

After talking with the design engineer, they suspect that one of the ICs on the 3.3 V rail has been damaged as opposed to the power regulator, though finding the component in question will be tedious. If you wanted to pursue fixing this, I would personally try to see if I can identify one of the 3.3 V powered ICs that either have a short or greatly reduced impedance between their ground and Vcc pins.

Let me know if you have any questions regarding this.

Thanks,
JColvin

[peterhu]

Hi @JColvin ，

Do you mean that the power regulator (TPS65400) is fine? However,the VCC1V8 also turns out to be wrong as 0V,but VCC5V0 and VCC1V0 that connected to another power regulator are correct,how to explain that? I am quite confused.According to your opinion,what should I test next to fix the board? Because there are so many VCC3V3 pins in the board.

Thank you for your advice, hoping for your further advice.

[JColvin]

Hi @peterhu,

The VCC5V0 and VCC1V0 working are okay because they are enabled first by the power sequencer, but your question reminded me that the 1.8 V rail was at 0 V which didn't fully make sense to me as the 3.3 V rail is enabled by the power sequencer after the 1.8 V rail.

So I double checked with the design engineer on their assessment and learned that they had missed the 1.8 V detail the first time around which should, of course, be working if only the 3.3 V rail was damaged. As far as I can tell, the 1.8 V rail is only used to supply the USB OTG chip and one of the Zynq PS banks which handle the Ethernet and Micro SD card, but based on your description none of these items were directly involved with the work you were doing.

I'll send you a PM for some additional instructions to pursue an RMA.

Thanks,
JColvin