Symptom: Red LED turns on after power-up, no screen display and the system cannot boot. Causes sorted from highest to lowest probability:
1. Power Supply Issue (Check first)
Insufficient output current: Raspberry Pi Zero 2W + MMDVM RF module requires high inrush current at startup. High-resistance USB cables or low-quality power adapters cause voltage drop. Try replacing the USB cable.
2. Display Issue
If the Raspberry Pi boots normally (green LED blinks) but nothing shows on the screen, the fault lies with the display. If the green LED does not blink at all and the system never starts booting, the problem is not with the screen.
3. Corrupted SD Card / System Image
The MMDVM Pi‑Star system is stored on the SD card. Abnormal power cuts, frequent hot plugging or long-term storage may corrupt SD card files and the system image.
Observe the green LED on the Raspberry Pi: it should blink during normal boot. If the LED does not blink, check whether the TF card is damaged. Insert the card into a card reader on your computer. If it cannot be accessed, replace the card and reflash the image using the official Raspberry Pi Imager tool.
Download the Pi-Star RPi image from the link below:
[https://www.pistar.uk/downloads/]
Tutorial:
[https://acceptdefaults.com/2022/05/08/setting-up-an-mmdvm-hotspot-dmr-with-pi-star-on-a-raspberry-pi/]
The Raspberry Pi board's green light is not blinking, which means the system was not written successfully. Try a different card.
Check the contents of the TF card on your computer. If the card is empty, reflash it with the Pi-Star system. If files exist on the card but the device still fails to boot, the RPi Zero 2W board is damaged.
4. Faulty Raspberry Pi or MMDVM Hotspot Board
Check the SVC light on the hotspot board: if it slow-flashes, the Raspberry Pi is the issue; if the SVC light does not light up at all, the hotspot board itself is the issue.
After reflashing the Pi-Star system, the Pi-Star Wi-Fi access point should appear within 3–4 minutes after power-on. If the hotspot network does not show up, the Raspberry Pi Wi-Fi module may be defective.
MMDVM board does not connect or work? — Test Method
Please test whether the hotspot is working via this link:
[https://www.m7spi.co.uk/mmdvmcal/]
If the hotspot works after the test, the problem comes from incorrect settings.
If the test confirms the hotspot hardware is faulty, please contact us and we will arrange a replacement unit for you.