• Please review our updated Terms and Rules here

Small 3D-printed C64 PSU

JNZ

Experienced Member
Joined
Sep 4, 2015
Messages
165
Location
Utah
I made this a while ago but only now tested it. I got tired of the large size of my C64 PSU and looked around for off-the-shelf solutions. I didn't find anything you could buy, but I learned that you could provide +5VDC and +9VDC and run the machine and many peripherals, sacrificing only the ability to power the Time of Day logic that depends on the usual 9VAC input.

I saw that someone did this by supplying a +5VDC @2A to a charge-pump voltage inverter, delivering +5VDC and +10VDC to a C64C: http://www.lemon64.com/forum/viewtopic.php?t=61160&postdays=0&postorder=asc&start=0

I decided to go a different route to ensure there was enough headroom for heavy power draw. I took two commercial buck regulator modules and wired them up inside a 3D printed case I made, and connected it up.





The boards glow a fairly bright blue that I may diffuse, though it's more intense in the photo than to the eye. I also made a black PSU case in which it'd probably be less intense. The DC input is from a 12VDC wall wart. A 3A one should do the job. The machine seems to work fine, including my SD2IEC.

Here are the modules ($2 each if you buy a pack of 6): https://www.amazon.com/RioRand-3-01-0076-Converter-Module-1-23V-30V/dp/B008BHAOQO

A AC/DC converter like this would work to power the modules: https://www.amazon.com/Selectec-12-Volt-Power-Supply/dp/B009ZZNHYC
 

gertk

Experienced Member
Joined
Jan 26, 2016
Messages
403
Location
Netherlands
Just my $0.02:

Unfortunately the 9Volts required for the C64 has to be AC and not DC.

Feeding it DC will stop the TOD clock function(s) of the 6526 chips, rendering the Basic TI variable silent (and some games/demos might not work anymore) and several devices connected to the user port change the AC 9V into other voltages (eprom programmers, RS232 adapters, etc). The 9V needs also be electrically isolated form the 5 Volt circuit (no common ground).

Depending on the type of SID chips used it could also be starving for proper supply (the 8580 type SID needs only 9 Volts, the older 6581 needs 12 Volt which is generated from the 9V AC by voltage doubling and stabilizing to 12 Volt which onl works with AC).

One other tip: put a TVS diode rated for 5V (6.3V max) over the +5 Volt inside the C64, these Chines modules have a tendency to wander in voltage or suddenly go haywire and emit the input voltage on the output resulting in instant death of most of the precious chips in the C64. A suitable fuse has to be put in series with the output of the 5V converter (2Amp).
 

JNZ

Experienced Member
Joined
Sep 4, 2015
Messages
165
Location
Utah
Just my $0.02:

Unfortunately the 9Volts required for the C64 has to be AC and not DC.

Feeding it DC will stop the TOD clock function(s) of the 6526 chips, rendering the Basic TI variable silent (and some games/demos might not work anymore) and several devices connected to the user port change the AC 9V into other voltages (eprom programmers, RS232 adapters, etc). The 9V needs also be electrically isolated form the 5 Volt circuit (no common ground).

Depending on the type of SID chips used it could also be starving for proper supply (the 8580 type SID needs only 9 Volts, the older 6581 needs 12 Volt which is generated from the 9V AC by voltage doubling and stabilizing to 12 Volt which onl works with AC).

One other tip: put a TVS diode rated for 5V (6.3V max) over the +5 Volt inside the C64, these Chines modules have a tendency to wander in voltage or suddenly go haywire and emit the input voltage on the output resulting in instant death of most of the precious chips in the C64. A suitable fuse has to be put in series with the output of the 5V converter (2Amp).

These are good notes, thanks. I did know that it'd make it incompatible with some (many?) peripherals, but I only intended to use it with my SD2IEC and C64 serial WiFi card. I had seen someone do something similar and he had reported about the TOD sensor not working as well, but it doesn't seem to be used all that often.

However, what's the downside of having a common ground between the 9V and 5V? I asked this on Lemon64 but no one could explain other than saying that that's how it was originally designed. There's a good reason, I'm sure.

Good tips about the protection diode and fuse too.
 

KC9UDX

Space Commander
Joined
Jan 27, 2014
Messages
7,468
Location
Lutenblag
In my opinion, you mainly don't want to connect them together because you cannot predict what kind of connection will be made on the other end. Hardware designers and hobbyists are likely aware that there is no connection on the power supply end, and are apt to make connections that are acceptable when they are isolated, and not when they are not.

A lot of my software makes use of the TOD clock. I expect a lot of other software, especially games, does too. But I could be wrong.
 
Top