Low volume, strange sound, hum in the audio output, missing bass, strong distortion – these are symptoms of aged or leaked  capacitors.

There are several types of capacitor used in cassette players – electrolytic capacitors, tantalum capacitors, ceramic capacitors, mylar, etc. Not all of them cause troubles, the most problematic ones are electrolytic capacitors and tantalum capacitors. Such faulty capacitors can cause severe damage, sometimes unrecoverable.

Electrolyte from leaked capacitor causes corrosion of copper traces. Result can be completely eaten traces on printed circuit board, released components, etc. In this case, repair is very difficult or almost impossible. I’ve seen several expensive players completely destroyed by capacitor electrolyte. Sometimes it also causes shortcircuit and damage of other components.
If there is a sign of faulty electrolyte capacitors, they must be replaced immediately!

Faulty tantalum capacitors cannot be distinguished optically from a good ones. Typical consequences are distortion, hum in the headphone output, uneven frequency characteristics, short circuit and burned components.

Do I always need to replace capacitors?

Some players are known to use capacitors that leak only very rarely (Sony DD models with center gear mechanics), while other are known to have always leaked capacitors (like cheaper Sony DD models with plastic mechanics – WM-DD10, WM-DD11, then most Aiwa players, early Panasonic models, etc.)
Those capacitors that survived 30 years, will probably work next several decades. But their specs are no longer as good as when they’were new. Usually it is drop of capacity and increase of ESR. Whether they will cause issues or affect sound quality, it depends on what is their function. Probability of failure of these old capacitors is high. Nobody wants to have their precious player damaged by capacitor leakage or short-circuit. That’s why it is highly recommended to replace all elcos.

Is it good to replace capacitors to improve sound quality?

Replacing capacitors because of sound improvement requires very high level of knowledge of electronics circuit design. In most cases, even using better quality audio grade capacitors does not automatically mean better sound quality. In some situations, it can make things even worse.

To minimize distortion, do I need to use capacitors with low distortion? Yes, but there are only a very few that will affect distortion. And capacitor type was given by producer, they knew very well which capacitor to use and where to use it. When you replace the capacitor, use the same type. Do not use ceramic capacitor instead of electrolyte if you are not familiar with electronics circuit design.

And basic question is: Do you really want your device sound perfect and sterile? If yes, connect headphones to your smartphone and that’s it. We do not live in sterile environment, there is lot of distortion everywhere around us. That’s why, for human being it is more pleasant to listen to analog music than perfectly clean digital sounds. Simply, when you like sound of your player, leave it as it is. If not, try to improve it, perhaps by changing capacitors, mechanical setup or getting better player.

However, in many cases, producers made some players to sound worse than the more expensive ones. And for that purpose they used wrong capacitor design. As an example, Sony WM DDII, WM-DDIII, WM-DD30 and WM-DD33 were designed in such a way that they are completely missing bass response. Get more expensive WM-DC2 or buy model with megabass circuit! Why should I switch player bass eq switch to “mid” or “high”? It should have flat response  with basic setup. End fix is so easy – just replace two capacitors and situation is solved. In some cases, it is good to use bipolar capacitors. Again, circuit design knowledge is needed.

What to use as replacement?

It depends on where the capacitors are located. I recommend to use Polymer Elcos wherever possible
– Polymer capacitors have very low ESR, lower than standard electrolyte capacitors. Also their aging porperties are very good.
– They are very small, usually produced for small voltage. It is not problem in walkmans
– They are easy to solder
– They do not leak
– They’re more expensive than standard capacitors, but it is no tragedy

If you replace tantalum capacitors, buy those marked as “high reliable, automotive standard”.

Where to get capacitors?

Buy capacitors only from trusted sources. Select only quality brands like Panasonic, Elna, Nichicon, Rubycon… You do not want your precious device to be damaged by fake capacitor. Even good capacitors are inexpensive.

For some models, you can get them here.

How to replace capacitors?
Answer is simple. Solder skills is required.

– I use hot-air soldering station to remove capacitors
– Then I clean PCB with IPA and cotton wool. It is very important to clean t well!
– Pads must be clean, apply new solder tin to their surface before you install new capacitor