This was my restoration project over the Christmas break. I was hesitant to even attempt this one, considering the state of the capstans and evidence of battery leakage - but it didn't look as bad on the inside, so decided it was worth a try. First problem - it was dead on arrival. Eventually traced the no-power fault to a shorted burnt-out coil in a tiny surface-mount transformer, hidden inside the DC-DC Converter module. I've posted another thread on this. With power now restored I tackled the cassette mechanism. The rusty capstans cleaned up surprisingly well with steel wool, and I borrowed a pair of pinch rollers from a sister model. Strangely, one of the pinch roller arms was tight on its axle and would not retract when reversing playback direction. I've had to file down the shaft (which also forms part of the head bridge) to give it some clearance. The motor was noisy so I've dismantled it and lubricated the bearing. One of the reel spindles was also stiff, which I traced to dried-up grease on a tiny idler gear. Accessing this requires the entire mechanism to be removed from the chassis, which is a tricky job with all the various PCBs still attached together with flex ribbons. In the process of doing this I'd also discovered that the head flex was split (looks like it's been pinched between the case and the back cover in a previous botched repair attempt), and also that the keypad PCB was corroded by battery leakage, with several traces open-circuit. I've repaired both of these by bridging gaps with tiny wires, in some of the most delicate soldering I've ever attempted! After a thorough clean, straightening the shell to get the lid catch to lock, and the unit reassembled and working, frustratingly the cassette sounded terrible! Obvious that the azimuth is way off. So I took out the head assembly again, and fully dismantled it to investigate. Bizarrely, I found that someone has stuck a tiny plastic washer under one side of the head mount, which tilts it at an angle and ruins the factory azimuth setting. With this removed and the whole thing reassembled, finally I have respectable sound quality! For a final touch I've 3D-printed it a new battery cover. This was by far the most difficult Walkman restoration I've attempted and the most complex model I've ever worked on. It contains at least four PCBs with active components, a couple more if you count the keypad and motor, and about 6 flex ribbons connecting everything together including the head and solenoid. Very satisfying to have brought it this far back to life, and I think worth it considering its rarity. It's still not perfect - my keypad repair is temperamental, the azimuth is slightly off in one direction, and the capstans have some pitting after cleaning off the rust. If I ever find a suitable donor unit I'll try to replace these. Interested to hear if anyone else has owned or restored one of these? Some photos...
Thanks, @autoreverser ! There is more to this story because I still wasn't completely satisfied with the sound quality. Browsing the web I came across some photos of other (F)701C's which also appear to have this odd plastic washer under the head assembly. It's visible in this link for example: https://img.canuckaudiomart.com/uploads/large/2353228-0ab64a76-sony-wm-701c-walkman-rare.jpg So it appears that this washer was fitted from the factory, and not some botched DIY repair attempt as I'd assumed. Either way it's a bit of a hack! The design of the tape guides on this model seems flawed... The black plastic tape guides seem to be completely redundant, since the spacing between the lugs is a good deal wider than the tape, so the tape never touches the edges unless it's severely misaligned. The grey plastic guide block glued to the head is much narrower, and seems to try to force the tape into alignment with the head. But on my unit the tape path forced by the guides was visible off-centre from the pole pieces in the head. I ended up shaving off a sliver of plastic from the inside of both the top guide lugs, circled in the pic below, to get the tape to cross the head centrally. With that done I then had to bend the metal head armature, by trial and error, to get good azimuth alignment. I tried with and without the plastic spacer washer, and ended up leaving it out. Now, finally, it sounds great! I've been enjoying my Dolby C encoded tapes on it. In the meantime I also restored a WM-F707, which also had severe azimuth issues despite being in almost mint condition (apart from an electrical fault). This model seems to have a later revision of the 701C mechanism, and does not have the spacer washer under the head. Again I had to bend / twist the head armature quite substantially to get everything back into alignment (but didn't need to trim the tape guides on this one). Curious to know if anyone else has come across head alignment problems with these or similar models?
