Here are some ways to revive an RPi
Try the pin method
sometimes the SD-card reader on the pi gets deformed over time, so applying some pressure on the SD-card with a pin or folded paper could work, also cleaning it with a brush works sometimes. refer to this for further explanation
You could try booting from a USB
(assuming your USB ports are in a good shape)
Flash a USB disk or you can just insert your SD-card into a USB SD-card reader
Since you are using an RPi-3b+ you only need to write
In config.txt then try booting.
If it doesn't work (USB disk doesn't get powered) then measure the voltage between
PP-2 and PP-27 or
PP-7 and PP-27 ideally it should be around
5V if it isn't then you could connect PP-2 and PP-27 like this over here or you could replace
U13 like done over here.
if USB does get powered but you can't boot then either
the Device is not supported or
the Device takes longer than 2 seconds to power up or respond.
Here are some supported USB Drives
- Sandisk Cruzer Fit 16GB
- Sandisk Cruzer Blade 16Gb
- Samsung 32GB USB 3.0 drive
- MeCo 16GB USB 3.0
If you are not using one of these, there is still a good chance that your USB drive is supported.
If all fails
If Nothing works then probably your RPi is RIP, if it is really dead then it will not read any 'Mass Storage Device' give any HDMI output, and have a cold Soc, some 5V GPIO sources may work, like for a fan.
If your pi isn't cold then there is some CPU activity but no storage to read so in this case you should replace the SD-card slot or USB slots however it's risky and might damage your pi, though it is worth a try since a working pi is better than a dead one.
You must remember that an RPi is a small computer the size of a credit card for $35 not some super-expensive gaming rig if it is dead then toss into a bin or replace it. Don't waste your time tinkering with an expensive red LED.
Hope this helps!