Hey folks, I’m working on bringing a Sony WM-30 back to life. It’s a gorgeous red model with a clean faceplate, absolutely no corrosion and the traces are all good. I replaced the belt and was able to get everything to spin up just fine, however when I tried to run it under load it wouldn’t play a cassette. I’ve identified that both reel gears are also split, which my understanding is that it’s a pretty common issue. I’m not worried about the gears, I’m going to replace those in due time. The main concern I am working on at the moment is trying to locate an acceptable replacement for the electrolytic capacitors. Once I replaced the belt I ran all the functions to ensure they’d work, however it seems once the unit had some time to warm up, one of the electrolytic caps leaked a little bit. I quickly cleaned up the substance with some IPA so I’m not worried about it corroding the traces, but of course I’m gonna give it a full recap before I try to run it again. My question here, is: what the heck are we using to recap these compact models? I’ve been consulting the service manual and I’ve also taken the unit apart to get eyes on the caps, and they’re all identical: 220uf 4V 85C, 4mm diameter and ~13mm tall with a 2.5mm through-hole connection for 4 caps in total. I’ve read about using tantalums for this, but I’ve had people tell me that tants make the audio too bright with too much treble and little bass, as well as requiring a higher voltage rating than the standard 4V (I was told to aim for 10V). I’m hoping you folks can help steer me in the right direction, this is a beautiful piece of hardware I’m eager to bring back to life.
SMD tantalums is pretty much the only viable replacement, as those long thin electrolytics are no longer made. Have been using SMD tantalums in other models like AIWA PX30 without any degradation in sound quality. I know there is a debate about this and some people say the sound will be 10x worse with tantalums, but that's just not the case. In fact some of the best walkmans (DD9 comes to mind) only use tantalums in the audio path. Same with later slim models and MD units.
I was skeptical about being told that the sound quality is really THAT bad, I figured it had to be user error or someone chasing audiophile status, but it was enough to give me anxiety about this. Would you recommend staying within original specs or should I be looking to exceed specs where possible, in terms of voltage? Like I mentioned previously, I was also told that I should aim for 10V instead of the original 4V if I didn't want the caps to fry when using tants.
The rule of thumb is the voltage rating should ideally be 2x the operating voltage. In case of the WM-30, the output coupling ones (C401, C402) operate at 0.6V, so a 4V rating is more than enough. There's no reason to aim for 10V unless those caps are more readily available and also in same footprint (not bigger). Same thing with C805, C609 both operate at 1.5V, so a 4V rating is already more than double. No need to aim for higher. If you find 6.3V in the same footprint as 4V, you can also use those despite not needed. But in walkmans usually size is the main factor that has to be considered. While it is true that tantalums are more sensitive, in this particular scenario where there are no voltage spikes or unregulated power supplies, the margin original spec leave is enough.
I still use electolytic in areas when I can get one that will fit but the problem is everything is mostly SMD now and so a lot companies stopped making some values and sizes . Sincerely Richard
