Hi all, I've got an WM-AF22 that is in really good cosmetic condition, overall very clean. I opened it up and replaced the belts (which I bought from Mihok), everything looks intact and in good condition. Initially sounded very very slow (like the reels weren't moving at the right speed), after playing around with the speed adjustment pot, even if the pitch sounds OK it is still warbly like there is very high W&F. I will put a speed test tape and measure W&F on my PC but wanted to start this post in case there are known issues. Thanks!
Did you lube the motor at all? Also, how’s the pinch roller? Clean and not hardened? Capstan cleaned?
The fact that it sounded very very slow initially is a sign that there is a lot of load on the motor and it can't maintain the correct speed. Tape speed should not need huge adjustment if everything is fine, only a minor fine tuning. The increased load can be caused by something rotating very hard from dried grease or a very tight belt (with much lower diameter than it should be). Increased load is also the cause of very high wow&flutter, so you need to diagnose and solve this first. Check by rotating everything by hand and see how the flywheels are rotating, how motor is rotating. In stop mode, everything should turn smoothly with almost no resistance apart from the tightness of the belt itself. When put in play, there will be some resistance due to the pinch roller pressing on the capstan, but it shouldn't be huge: you should still be able to rotate the mechanism with the tip of your finger, without much resistance. Check the belt first, as it's possible that the previous owner installed one of those cheap Chinese belts, sold in packs of 50 at 3$ (which typically have a wow&flutter around 1% WRMS).
I just repaired an AF23 this morning - similar mechanism, similar issue to yours. Turns out the pinch roller tire had been pushed up against the bracket that holds it, causing friction. They are a snug fit on their hub, but this one had slid on its hub enough to cause the issue. I replaced the pinch roller assembly with another I had on hand. Plays great now!
When reparing walkmans with this mechanism, I always check the yellowish drive gear on the front side. They're usually almost completely frozen to the axle. Though I think this may be somewhat of a climate affected issue?(It's rather hot humid here in the tropics) Since I don't ever see this issue reported in the forums. They use a different plastic there and I don't know why, but the metal axle will corrode and get stuck to the plastic. Kinda weird, since it's only happening on this Sony mechanism.
