Good afternoon everyone. I recently managed to snag a silver WM-EX7 with the original remote (lacking earbuds), AA battery attachment, and carry pouch (for under $60). Cosmetically it is very good, only some light scratches. I knew prior that this mechanism (along with my EX677) could fall victim to the tac-tac sound described by Valentin in his thread. So once the Walkman came in, I removed the old stretched belt, and ordered a new one + a new gear if I needed it. Today the belt and gear came in. I replaced the belt and it played near flawlessly, speed was good, wow/flutter was low as well (for a portable anyways). Unfortunately, I noticed this very rapid ticking noise. Its less so like a tac-tac noise as described in the linked thread, so I want to double check here before I solder off the board. Also, I saw that the replacement gear gets glued to the metal disk. What type of glue should I use if I need to replace it, suggestions? Here's a short video of the previously mentioned noise. Please ignore the fan in the background. And a final note: It works perfectly with the cover off, but when I put the cover back on, it refused to play correctly. Not sure what's going on there. More than likely I just assembled it wrong, but I figured I'd better not leave any details out.
Update: Went through and desoldered the board to get a closer look. Slight crack in the gear, but because the ticking noise was so low, I decided to keep the current gear for now. It almost sounds like normal operation. But, I screwed up. After I resoldered everything back together and then replaced the screws, it plays WAY too fast. The best way to describe it would be like someone was singing having breathed in helium, or how a mouse sounds (squeak wise). Looking over the board again, I rechecked my solder points, they were nice and shiny. Nothing flowing into each other either. However, I noticed I may have nicked this transistor chip (right side) when soldering some of the motor connections. (See attached diagram and photo). It is listed as motor switch. The operation of the motor works perfectly fine, goes into play/rev, FF/REW, but the speed is just way off. Would this be the culprit for the increased speed? Or is there something else that I may be missing which is causing the issue? Any help is appreciated very much so.
Liquid super glue is what I used. Don't know if I have updated the original thread or not, but there are 3 potential problems in regard to the tac tac sound: - the clutch gear itself (this is by far the most common), which creates a low frequency tac-tac, about once every 2 seconds; - the small gear on the flywheel that drives the geartrain (this is less common), which creates a high frequency tac-tac, many times/second; - the idler gear between the flywheel and clutch (very rare, seen it once), creates the same noise as the clutch when warped; In all situations replacing the defective gear is the only fix. The unfortunate part is for points 2 and 3, a donor unit will be needed. This is a transistor array that drives the motor, but in the last picture I see nothing wrong with the IC. The small chips on the right side don't seem a big deal at first glance. The symptom I would expect to see if one of the phases would be missing is lower speed and hiccups. Does the speed trimpot actually do anything or speed is fixed regardless of setting ? It's also best to double check everything you have done, including small SMD resistors and capacitors (those around IC601 motor servo) that may have been nicked accidentally.
I do have a donor unit, a FX675, which I was going to repair until I needed one of the pinch roller brackets for my EX677. Judging by the sound in the video I linked, it may be the small gear on the flywheel that you have described. I can open both units up later and check to see. The speed trimpot does actually adjust the speed, now it never adjusted it back down to a normal level, just super fast, or super super fast. Will do, more than likely I nicked something else and I haven't noticed. Going to get some liquid superglue today (misplaced the last bottle awhile ago).
Watched the video now and I agree the small gear on the flywheel seems to be the problem. Before commiting into removing, check that both units use the same flywheel as there are more versions: - some are brass, others are plastic; - some have the retaining split washer on top, others on the botton; Looking at the schematic, most of the components related to speed control are on the bottom side of the PCB (see pics attached). So I would double check soldering to the motor first, even if it looks good.
I will double check my soldering job tonight, it is very possible there's a cold solder joint. I appreciate the follow up Valentin. Update: Had a unfortunate family emergency yesterday afternoon. I wasn't able to check. I will update this post further when I get a chance.
Longhorn, Good luck and sounds like your on the right track ! I am currently working on a Zenith Royal 500 radio with a bad solder connection and using my microscope I found hairline crack ! Sincerely Richard
