RE: Picking aluminum polymer electrolytic capacitors for the C64

bedfellow — Sat, 06 Sep 2025 16:04:44 GMT

If like me you replace the electrolytic capacitors on a 250407 C64 board with polymer electrolytic capacitors and you you use a modern switched mode power supply, you may notice a high pitched noise on the audio output. In my case I found it was due to replacing either C34, C62 or both (Vcc and Vdd supplies to SID chip). Swapping them back to traditional electrolytic capacitors eliminated this noise for me.

RE: Picking aluminum polymer electrolytic capacitors for the C64

clem57 — Sat, 10 Aug 2019 12:28:32 GMT

First time seeing this and feel you cannot get enough of this great blog!.

Keep it coming.

Clem

RE: Picking aluminum polymer electrolytic capacitors for the C64

COMPACT — Sat, 10 Aug 2019 08:17:53 GMT

Rules of Thumb? Just listen to Bil Herd himself on the matter.

[View:https://www.youtube.com/watch?v=PYDn9idlWb4:740:466]

RE: Picking aluminum polymer electrolytic capacitors for the C64

baldengineer — Sat, 27 Jul 2019 17:13:39 GMT

Question from Kevin on Twitter:

Did you use radial caps for C19, C88, & C90 on your Commodore 64? I wasn't sure if axial caps can always be used in place of radial as long as the capacitance and voltage matches

In this case, I wanted to use Polymer Aluminum capacitors. As I pointed out in the video, there are no axial polymers available on the market. So I ended up using radials and just cheating a bit with their leads. For improved performance, I should look to see where I can shorten the ground loops, but that'll come at a later time. (and does not matter as much in a linear regulator circuit.) Additionally not shown in the original video, I hot glued the leads to the PCB. Since there is no out-gassing from polymers, there is less concern about "potting" them.

For more information on Polymers check out The Learning Circuit 40: Learning About Polymer Capacitors video. If you'd like to see some measurements I made before and after using polymers, then watch The Learning Circuit 42: Replacing MLCCs with Polymer Capacitors video.

For THIS circuit, the most critical parameters are the voltage and capacitance. The ESR of the caps is less critical since these are linear regulators. You'll notice in this schematic that C88 and C90 are rated for 50 V, while C19's rating is 16 V. I have noticed some guides on the internet suggest you can use 16 V for all three of these capacitors. Please note, YOU CANNOT USE 16 VOLT FOR ALL THREE OF THESE CAPACITORS. On some C64s, C90 is rated for 25 V. So when possible use the same or higher voltage. C19 sees about 20 V while in operation.

In general, yes, you can use axial or radial if the cap and voltage matches.

I also came across axial polypropylene film capacitors.

Today, axial film capacitors are far more common than axial polymer aluminum capacitors. Since ESR is less critical, you could use a film capacitor. Although, I doubt an axial PP film capacitor would be smaller than an aluminum electrolytic.

Last, a point of confusion for everyone is the use of the word "Polymer." In an Aluminum capacitor, polymer is the cathode. In a film capacitor, polymer is the dielectric.