3.3V Shorted to 5V

[K9EQ]

On a ZumSpot purchased from HRO with the Pi Zero W, I noticed that the 3V3 and 5V Power (pins 1 and 2) are shorted together! Huh? A DVM measurement shows that the ZumSpot board is getting 5V and the 3V3 line on the PiZW is 5V. Shorting pins 1&2 shorts the input of the 3V3 regulator to the output, so we'd expect 5V where ever one was suppose to have 3V3.

Obviously that can't be right!. The short was caused by, what appears to be, an intentional solder jump between pins 1 and 2 on the back side of the PiZW board. So naturally I removed it.

Now the PiZW won't boot!!!!! Nothing. Nada. The ZumSpot boots okay and is quite happy. I confirmed that the 3V3 is actually 3.3V and that 5V Power is actually 5V. But it won't boot.

I replace the short between 3V3 and 5V Power. Now the PiZW boots and the ZumSpot is back to running on 5V.

Any thoughts on this? Strange!

73,
Chris, K9EQ

[KE0FHS]

This is what I heard was changed on the ZUMspot v0.6 released Jan 2019:

• EMI (ElectroMagnetic Interference) improvements
• The I2C connector moved to make make it easier to mount 0.96″ and 1.3″ OLED displays
• The SDA/SCL pins for OLED now connected to the GPIO pins (previously to the STM32 pins)
• The voltage supplied to the Nextion port changed from 3.3V to 5V
• Two new LEDs added: NDXN and MODE (other)

This is my opinion only: I think probably the 3.3V was upgraded to 5V because some people were having trouble running larger Nextion displays on 3.3V. My smaller Nextion displays (3.2" and 3.5") ran fine on 3.3V, but they'll also run fine on 5V.