Vintage 1970s Sony Tape Deck Repair Part 2!

This is part 2 of my quest to turn my Sony TC-K96R cassette deck, the most broken piece of audio equipment I've yet encountered, into something I can actually use and listen to. It has been a journey! Go watch part 1 if you have not already: https://youtu.be/pP7Df89-UM0 In part 1, I made the deck mechanically sound and fixed some power issues that had rendered the output completely kaput. Now, in part 2, it's time to tackle the sound quality, which was just plain bad in playback and a complete disaster when recording. I admit I talk a lot in this video. I originally had close to 4 hours of footage, of which about 3 hours was actual project work and 1 hour was me explaining stuff. It was a long process that took about 2 months and involved a heck of a lot more than you actually see in this video, with many red herrings along the way that added up to nothing (I left a few of those in, but not all). In the end, most of the work footage just looked exactly the same, so that's what I cut out more of. But I ended up with about 30 minutes of explanation and 30 minutes of project footage, which is not the ideal balance. C'est la vie. This repair took so long - and ultimately the goal was the repair, the video just documents it - that I just need to be finished and post this video as it is. There may or may not be a part 3 someday, but I'm not really planning on it. Here's another link to my Fnirsi 2C53T that I use throughout this video for measurement: https://amzn.to/4iIUxcY (That is an affiliate link and I will get a commission if you purchase. This video is not sponsored by them; I just like the product and this repair would not have been possible without it, or at least something like it.) Music credits: Sea Lemon - Vaporized She is great and you should check out her bandcamp page: https://sealemonmusic.bandcamp.com/ National Sweetheart - A Prairie Dog Windows of Ken - Glo-Fi Dan Henning - Eternal Garden All from the YouTube Audio Library. 00:00 Intro 02:07 Fixing playback 14:10 Status update 16:32 Start of recording repair 20:09 Closer look at the record circuit 26:54 Working on Dolby stuff 36:02 Tracing the waveform 41:26 Status update 2 - a Eureka moment 47:38 Disabling record muting 51:44 Calibration and bodge wires 55:31 Playing music! 57:04 Revisiting record muting