jammincomedy wrote: ↑
Mon Oct 15, 2018 7:04 pm
Hello. I have four Raspberry Pi 3's that I am using. They are all connected to a VGA monitor with an HDMI to VGA adapter. The first day, all four of the PI's turned on the monitor displays. However, the second day, two of the displays would not turn on when plugged in to the Pi's. The monitors are fine as a Windows computer will turn them on. I also tried the Pi's that weren't turning on the two monitors on the other two monitors where the Pi's were working, and the two non-working Pi's would also turn on those monitors.
Is there anything I might check in the monitor settings that could affect its ability to pick up the Pi's? The Pi's have their resolution set to default monitor preference. Thanks.
The first thing to try is to make sure you have the monitor connected and powered on *before* you power up the Pi. This is because the Pi only looks for a monitor when it starts up. If it can't see a monitor at startup, the HDMI output get disabled. There is no auto-detection once the Pi has started up, so plugging one in after boot won't do anything - the HDMI output will stay disabled.
(Also, if the HDMI to VGA adaptor uses its own separate power supply, that obviously needs to be connected and powered on before your power up the Pi).
Also make sure that your Pi has an adequate power supply - the official power supply with the Raspberry Pi logo on it is recommended.
Failing that, you may just be unlucky and have 2 monitors that cannot be reliably detected at boot time by the Pi. There are various settings that can be used in /boot/config.txt to get around this (including hdmi_force_hotplug=1), and also to get around the fact that auto-detection only works at boot time, which is annoying. Try the simple fixes first though, as most monitors do work correctly.