Originally posted by: BUB In the late 80s and early 90s, the Walkman 150 mechanism replaced the earlier WM10/40/100/501 mechanisms and propagated across the midrange of Sony's Auto Reverse line. Unfortunately, they don't seem to age very well as shrinking plastics cause some of the gears to crack and split. In the many examples of this mechanism I own, I've yet to see an intact clutch assembly. A broken clutch gear causes the unit to either eat tapes (as the takeup reels jam) or jam up altogether. There are other faults with this mechanism, as the FWD takeup reel gear has a tendency to split as well (and eat tapes), and on later series (WM-190 onwards) they get a new disc type motor that has reliability issues. Here I've got 2 WM-150s, an export and domestic model. The difference is that the domestic model has some lovely engrish nonsense written on the lid. (I bought a 2nd WM-150 for its battery box, so I have 2 of them now!) You can ID a WM-150 mechanism by the rectangular buttons and the EX Head Script sticker on the reel table. I've been looking for a way to reliably repair the clutch and I think while this method is crude, it seems to hold up well so far. I've tried this method a couple of times now and after using these two units regularly for over a year and 6 months respectively, I think this repair holds up quite well. Unlike the clutch of the Walkman DD, the clutch in this mechanism is tiny and under constant tension and pressure. For this reason epoxy alone won't really work. Here's the offending broken gear:
The clutch consists of 5 components: The broken clutch gear, The large driver gear, The friction pad, The grey clutch, and a pressure spring. The pressure from the spring presses the grey clutch, friction pad, and driver gear together to create a slipper clutch, allowing the take up reel to rotate at different speeds while providing constant torque. The Clutch Gear then drives the take-up reels. On the other side of the driver gear is the optical sticker that allows the photo sensor to detect reel rotation. Here's why the clutch gear breaks: it is press fit into the grey clutch, having a hole just slightly smaller than the grey clutch's spindle. They are meant to spin as one unit. Over time as the plastic shrinks the pressure builds and cracks the gear. The combined force from the pressure spring causes the whole clutch to pop open. The fix is to weld the broken gear back together, then remove all pressure from the press fitting so it won't split again. The gear is welded together with the tip of a soldering iron. It looks terrible, because it kind of is. Add glue, weld together both sides, avoiding the teeth. The next step is to increase the diameter of the hole in the clutch gear and reduce the diameter of the grey clutch so that they fit without any pressure. To accomplish this, I used 1000 grit sandpaper and a pin vise fitted to a rotatory tool. Still looks terrible. The two components now fit loosely together. Now is a good time to assemble the clutch together without the spring to make sure it spins freely in the mechanism without any kinks. Now we put the whole clutch back together int he correct order, but since the press fit is gone, the clutch won't stay together under the pressure from the spring. Since the Grey Clutch and the Clutch Gear moves as one solid unit, I weld them both together. Yes. First I glue them both together so that they stay together for the welding. Then very carefully, weld the spindle of the Grey Clutch out into the Clutch Gear. You kind of get 1 shot at this, but so far I've yet to screw up. At this point it looks absolutely abysmal, but the clutch works properly again! The next step is to clean up the hole on the Grey Clutch with a pin vise and sandpaper. It still looks terrible, but the function's more important here. I guess. That's it. As long as the welds hold, the gear should perform like new... as long as you didn't screw up any teeth. This particular WM-150 was missing a C-Clip on the Reel Table Flywheel, so I replaced it with a wire wrap. Provided there aren't any other broken gears, the mechanism should work! (Wow and Flutter shouldn't be adversely affected if the teeth are ok) I also replaced the capacitors in what is possibly the easiest Walkman to re-cap: only 2 through hole caps! When repaired, these are very nice Walkmans, very good sounding, EX Amorphous heads. The DBB circuit is actually quite pleasant to listen to on the Mid setting. The 550C adds Dolby C. Some other notes: The battery box design is rubbish, as the screw pin isn't fixed to the battery box and is difficult to put on. Azimuth adjustment is not possible, but as my 2 units have very few hours on them, the heads and pinch roller are still new and give good azimuth in both FWD and REV. My other examples (WM-2091, GX50) don't perform as well. If anybody has a better (and cleaner) method to fix these thing, please let me know!
