By popular request, I am posting a repair tutorial for the aforementioned Sony walkman from 1989. If you have worked on a WM-701c before, you will immediately enjoy working on the F707. Although it's even more complex, the design and layout is much more straightforward. While the 701c truly feels cobbled together when open, the F707 has just one monolithic PCB (aside from some minor flex boards) and feels much more robustly designed. For instance, it has true copper screw thread inserts in the plastic chassis, avoiding the dreaded "broken threads"-syndrome that you encounter in so many other Walkmans. It is also much more neatly laid-out in general. For those interested in the tech fine print: The Walkman mostly contains just one PCB. This board is two-sided. Side A is the one facing you, side B is the inside facing the cassette. It makes use of 3 different voltages: 1,5V (from the battery), 2,4V and 3,6V coming from a converter that is housed in the little copper box the lower right corner. The miniaturisation level of the board is quite astounding for 1989: all traces are minuscule and you should avoid ripping any pads as reconstruction would be difficult. Also note that the vias (of which there are plenty) are sealed and not bored through the PCB, making the use of botch wires impossible without boring through the board first. 1. You begin by opening up the chassis. Refer to the service manual here for this procedure. It's quite straightforward. This is what you'll see (I am angling the view a bit so you can also see the arrangement of the input buttons): IMG_0448 by Fulltimehuman posted Jan 1, 2022 at 7:06 PM 2. The important pieces here are: the flex cable at the top left, the black, yellow and white cables that go from the front of the board to the back, 2 screws, and — important! — two plastic prongs at the top of the image that hold the board in place (marked below). Remove the two screws and remove the flex cable by opening the push-down-clamp with your fingernail in an upwards (!) movement and pulling out the flex cable (marked below). Do not use pliers or any sharp instrument. Then loosen the two prongs carefully. IMG_0449 by Fulltimehuman posted Jan 3, 2022 at 3:18 PM 3. Fold down the PCB towards you while fixing the upper part of the device using some sort of instrument against which you can lean it. You may also want to use a "third hand". Note that the + pole of the battery is just a lose piece of metal that will fall out when you remove the PCB. It's supposed to do that. You will now see 4 SMD (surface-mount) caps and a number of smaller THT (through-hole) caps. The former 4 need to be replaced. They are the four silver "buckets" that clearly stick out from the rest (marked on the second image below). Their values are: 2x 220uF at 4V, 2x 47uF at 4V. Both capacities are still readily available. When ordering, play close attention to diameter and height! You will want to order the smallest versions available (about 4-5mm in height). You may have to unsolder the aforementioned wires now to gain some more room to manoeuvre. Unsolder them from side A of the board to make it easier — possible, actually — to solder them on again later. I would advise against trying to replace the THT caps. Firstly, they are far less likely to fail and likely ok, if they're not visibly leaking. Secondly, they are partially of hard to obtain capacities. Thirdly, they are in part weirdly shaped (very long and thin), making them still harder to obtain. And, fourthly, some are mounted to fragile flex boards. IMG_0451 by Fulltimehuman posted Jan 1, 2022 at 7:06 PM 4. You will begin by removing the old SMD caps. Important: Resist the urge to grab the soldering iron, heat the visible tin legs and push the caps upwards. This will almost certainly rip their pads as their legs extend inwards and any heating of their visible outer parts does not heat the inner parts enough to remove them cleanly from the pads. I strongly advise to use the method of cutting the cap domes off with sharp cutters and then remove the remains carefully with a spudger, like so: IMG_5128 - 01 by Fulltimehuman posted Jan 3, 2022 at 3:18 PM 5. After removal, heat your iron to 270C, add some leaded solder to its tips and clean the pads of all old solder by tinning them in one go (using flux). You should cover nearby parts with Kapton tape as there are some plastic switches in the area. The result should look something like this: IMG_5131 - 01 by Fulltimehuman posted Jan 1, 2022 at 7:06 PM 6. Putting the new caps in should be a fairly straightforward process. You should tin the pads with some solder first: IMG_5132 - 01 by Fulltimehuman posted Jan 1, 2022 at 7:06 PM 7. After soldering the 4 caps in, everything should look pretty much like this: IMG_5134 - 01 by Fulltimehuman posted Jan 1, 2022 at 7:06 PM 8. Do not forget to clean off the remaining flux with isopropyl alcohol. You may now repeat the first steps in reverse order and should be finished. IMG_5130 - 01 by Fulltimehuman posted Jan 1, 2022 at 7:06 PM Let me know if you run into any trouble and I'll be happy to help. Should you also need a belt for the Walkman, you may find one here.
