Recently I read Valentin's excellent article about restoring the Sony DD9, and I think it's one of the best restoration guides available. https://stereo2go.com/forums/threads/wm-dd9-restoration-tutorial.11142/ I recently restored my own DD9, and these are the steps I took: Replaced the drive belt, rubber tires, and pinch rollers. Regarding the pinch rollers, I personally don't recommend replacing the original ones unless they are actually worn or damaged. The original pinch rollers in my DD9 had obvious grooves worn into them, so I replaced both of them. After removing both capstans and flywheels from the chassis, I cleaned the two capstan bearing holes (the holes that the capstans pass through) using small cotton swabs and isopropyl alcohol. English is not my native language, so I used ChatGPT to help translate this post. I hope it clearly conveys what I mean. Applied a small amount of watch oil to the base of both capstans before reinstalling them. Lubricated the front bearing of both motors with a tiny amount of watch oil. Used the lubricant very sparingly and made sure it didn't spread to other parts of the mechanism. I did not touch any of the plastic gears inside the DD9. I did not remove the head assembly for cleaning. Before inserting the first cassette after the restoration, I thoroughly cleaned the entire tape path, including the capstans and the playback head. Fortunately, this DD9 had no electronic faults, so I didn't need to solder anything onto any IC pins. That was a huge relief. After the restoration, the W&F in forward playback measures approximately 0.04–0.06% WRMS, and I am extremely happy with that result. However, the reverse playback W&F is around 0.10% WRMS. Although this is noticeably worse than forward playback, I currently don't know how to improve it any further. In my opinion, there are some factors affecting wow and flutter that we can address, such as replacing the belt, rubber tires, and pinch rollers. However, there are also factors that are beyond our control—for example, weakened motor magnets, tiny metal or plastic debris inside the motor, or even an imbalance in the flywheel that has existed since the day it left the factory. Problems like these are virtually impossible to fix unless you have specialized equipment, a microscope, and the skills of a surgeon performing microsurgery. In the case of my DD9, I suspect that the only way to further improve the reverse playback W&F would be to replace the reverse motor or its FG coil. Unfortunately, both the DD9 motors and FG coils are unique to this model and were not used in any other Sony Walkman, so inexpensive donor parts simply aren't available. Overall, I'm very happy with the results of the restoration. Unless I find a way to improve it further, I'll simply enjoy listening to this DD9 and appreciate the music it brings me. I'd love to hear from other members. Do you have any tips, tricks, or experience for improving W&F in Walkmans? I'd really appreciate it if you could share your knowledge here.
There are a couple of things that can be tried to improve the W&F on REV, although success highly depends on cause: 1. Can sand the motor spindle to remove any imperfections in the surface; 2. Check/adjust the motor position so it's perpendicular to the flyweel; 3. Check for any rust spots on the REV capstan; If identified capstan can be sanded (while rotating), but keep in mind reducing the diameter will also reduce the speed on that side. 1 and 2 is something I always do (on all DDs) and can tell these can improve the W&F although not by a lot (like don't expect it to drop in half from this alone). On DD9 specifically have seen rusty capstans to cause increased W&F. So if any pittings are visible, that's rust. When it comes to motors, FG coil, flywheel: 1. Motor can be a problem (weak magnet, rotor touching case/magnet) however unlikely. Also motor would cause flutter, which I don't see in your measurement. Rather I see a 7-8Hz peak (not visible in FWD measurement), which would rather suggest it's capstan related. 2. FG coil that either works or it doesn't, won't create high W&F. 3. Flywheel balance could cause a wow, although given the system operates in a servo loop, it can compensate for some minor imbalances unlike a belt driven unit.
