rpi3 a+ will not boot

[a+user10]

i have had my raspberry pi 3 model a+ become a paperweight after NOOBS refused to boot.
when i plug in my pi (with a NOOBS sd card of course) only the red led is lit, and nothing is displayed to the connected monitor.
i suspect a eeprom corruption after the pi refused to blink green when powered without a inserted boot medium
but i can only find bootloaders for the pi4

[FTrevorGowen]

i have had my raspberry pi 3 model a+ become a paperweight after NOOBS refused to boot.
when i plug in my pi (with a NOOBS sd card of course) only the red led is lit, and nothing is displayed to the connected monitor.
i suspect a eeprom corruption after the pi refused to blink green when powered without a inserted boot medium
but i can only find bootloaders for the pi4

A P3A+ does not have an eeprom so all the firmware etc. resides on the uSD card apart from a smaller, simpler, OTP bootloader in the SOC. It's likely that either your NOOBS card has become severely corrupted or has failed completely. Unless you need to boot more than one O.S. from a uSD card, try writing a fresh RPiOS image via the new tool etc.** to a new card. (NB. NOOBS is not an O.S. but an O.S. installer)
Trev.
** https://www.raspberrypi.org/downloads/

[DougieLawson]

I'm assuming you're a Windows user, so use https://downloads.raspberrypi.org/imager/imager.exe to write a new SDCard and that should boot without any struggles.

If it doesn't boot then either your power supply is junk or your RPI3A+ is junk.