So I recently got out the old PSP (1003), it has a chip in it (diluted platinum, epsilon chip), but this is very old and outdated and as far as I know unsupported anymore, so I decided to try to install GEN D-3 instead to play newer games. To do this I updated to 5.03, used ChickHEN and then installed GEN D-3. This all worked fine, up until the point where I turned off the PSP, and now it won't turn on again. I think I know exactly what I did wrong. There was an UPDATE folder which I was meant to copy into PSP->GAME when installing GEN, but instead of doing that, I mistakenly copied the EBOOT.PBP from the UPDATE folder and replaced my old EBOOT.PBP with it. Yes I realise this was probably very dumb and I only have myself to blame.

Now that my PSP is seemingly bricked, with the chip, holding L or R when starting up the PSP will only bring up the epsilon recovery menu for the old chip, of which all of the files are missing and so none of the options work, apart from, however, the USB connection mode.

tl;dr I'm looking to see if there's a way to unbrick the PSP using USB connection alone since that's all I have access to right now.