Work in Progress
You might have the capacitor connected to the board. You need to remove it when you want to flash. Remove it and re-add it when you're done flashing.
If you still have an old firmware (< 1.10) you need to set up the LCD pins as defined on the page of your board.
Also, you probably need to set the contrast potentiometer correctly.
Note that brightness control in the firmware may not work. You need an extra wire that is not included in the kit or re-purpose the RST wire.
Normally the OAT doesn't show any debug messages, as it might mess up communication with the controlling application. You can try setting:
#define DEBUG_LEVEL (DEBUG_ANY)
and re-flash, then see if you get some messages. The last one should be Boot completed. If that went fine, you need to comment this again and re-flash, as the messages will break client applications.
See the Troubleshooting page for a description of how to do this.
In order for the firmware to work, the configuration and the hardware MUST match. If you disconnect something (LCD, drivers, GPS, etc) you MUST update the firmware configuration to match.
(the reason is that some peripherals need blocking reads/writes, so if nothing is there it simply can't continue)
The hissing is normal, it just means that the steppers are powered and holding position. If you're using TMC2209 drivers you can enable stealth mode in your local config:
#define RA_UART_STEALTH_MODE 1
#define DEC_UART_STEALTH_MODE 1
but it is recomended to leave it off because stealth mode degrades motor performance.
Depends on the type, only A4893's and TMC2209/08 drivers are supported. Note that the A4983 drivers are 1/16th the performance compared to TMC2209s.
The steppers are half the performance if the recommended 0.9° stepper. It'll work fine, but your guiding/tracking performance will be proportional compared to what others achieve. If you're doing <50mm FL lenses with a typical DSLR sensor, it'll be good enough. But if your pixels are tiny with a longer focal length, you'll notice it.
You may need to play with the timezone in the INDI settings, INDI doesn't strictly follow the Meade serial protocol. Increase/decrease the timezone until the OATs reported HA and the real HA match.
The designed latitudes are from 20°-50° (North/South) in increments of 10°. You should select the designed latitude closest to where you will be using the OAT. Any major latitude discrepancy can also be resolved with the OAB (Open Astro Brick 🧱) Simply prop up the back/front until you can adjust with the front/back screws.
The consensus seems to be PLA, not PETG as it's stiffer. Some folks also used Carbon Fiber Nylon.