Walkman 150 clutch repair

This is a repost of my old thread.

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!

 

hi. thanks for posting this!
it will save lots of machines - I hope.
(I just did the glue-version 2 days ago, and it does not work - the reel just stops after few turns,
which confirms your approach: making the hole bigger is a must!)
cheers!
M.

 

Which is why I also suggest welding- it should be stronger than most glues (they won't stick to the nylon)

 

I would like to try this repair process since i have 2 WM-150 and both dont work. motor run but something doesn't let the gears move

So where is this clutch exactly?? can you please mark it on this picture? Thanks

 

Be careful, the clutch Assy is already broken and may flt apart when you remove it!

The highlighted Takeup gear is also commonly broken.

 

thanks for sharing that guide with us again - super helpful

just repaired / recapped a wm-f550c - unlike with previous machines, I botched the welding on the clutch but found one I could use from another machine

sounds good but plays backwards when auto-reverse is activated - I can live with that, although suggestions appreciated

I love this series and have about 10 walkmen with this mechanism - really fond of my WM-GX50 which sounds really fantastic. But sadly that clutch is a PAIN. Hoping for a marian-style replacement part one day!

Don't suppose you have a service manual for the F550C bub? a bit unsure about some electronic adjustments - dolby level trim pots from memory...

 

Thanks bub
You are very helpful

 

Wow thanks for posting this Bub, I have one of these and, yes, you guessed it, it doesn't work. If the clutch is broken on mine I may just leave it but at least I'll have a photo of how the belt fits! I need to find a battery box too mind, but it does have its leather pouch.

 

hi,@bub ,@sickly_b ,@Boodokhan
I think you will love this photo.

 

The picture shows the central gear for DD series right?
Do you have the solution to clutch repair? or have you designed something to replace the cracked clutch?
Are those gears shown at the button new one made for WM-150?

 

The big gears are for DD, the small gears are for ‘green button’ Walkman such as WM-150, it’s newly made just for replace the cracked one. You don’t need to repair the cracked gear anymore!

 

When is it available for sale?

 

I'd love to try your replacement gear, David! Looks great. Is it resin cast?

68mm belt 0.8mm thickness or thinner will work, but mikholm's belts are excellent and are the lowest wow/flutter for this model I've tried, depending on sample.

 

Hi,

did already someone get the new small gears for ‘green button’ Walkman such as WM-150? If yes, where to buy?
I have a WM-550C and WM-F550C with cracked plastic gears and would like to try a repair.

 

Did this ever come to fruition?

 

member David-ease disappeared. He has not been active within last year

 

Ah, yes, I see that. Too bad. So our best option is Bub's repair tutorial (this thread), yes?

 

Thank you for your guide, I think I have the same problem, so I'll see. Anyway I have some questions)

What was the reason ?

And can you say size of belt for wm-150, please ?

 

Belt is 68mm