My First was Machine Code on an RCA 1802 microprocessor.
Same here, but I still have my old computer and have replaced all damaged parts and undone all (not always wise) 'improvements'. It's now in good shape again and that's how it's supposed to stay.
Sometimes I still write some code for it, but now I have become lazy. I use a cross-assembler on the PC and then transfer the binary. As a WAV file I simply connect the PC's audio output to the old computer's cassette input, play the WAV and load it. 10 years ago I wrote a program that can load WAV samples from the old cassette tapes and reconstruct the binary files on the PC. This way many old programs could be rescued and made available to other users over the internet. Creating a new WAV sample from a binary file to play to the old computers was not so hard after that.
Ooops, that reminds me again to keep my promise to finish a new version of that program, which supports the tape formats of the Netronics Elf II, Quest Super Elf and now also the RCA VIP.