Commodore 64 Power Saver (Revision E)
Why do you need a Power Saver for the Commodore 64? Basically, Commodore intended the computer to live for a maximum of 5-6 years and so the components chosen reflected this view - no thought went into considering what happens past this point. Now that it's 30 years later we know that the 5v regulator has a tendency to short out input and output voltage, meaning that those sensitive 5v chips will intermittenly, or sometimes even permanently, end up getting something like two or three times that... enough to melt that precious silicon! Your options are either to get a brand new power supply or combine your old one with a C64 power saver for as long as that'll still be around, running unprotected is simply foolish these days!
How does it work? The design is based on the one developed by famed C64-tinkerer Ray Carlsen, what it does is monitor the 5v line coming from your power supply and when it starts outputting voltages above 5.6v a relay is slammed shut and the line is cut. You have the option of mounting a buzzer to the board so that you can get annoyed at it until you realize it's time to buy or build a new PSU, or when mounted externally you can look at the nice LEDs to figure out wether your supply is good or not. Once a PSU has started to go bad, put a "Bad PSU" sticker on it and never use it again!
Complete BOM and pictures of the completed boxed version of this can be found on my github, see link to documentation.
NB! Some Commodore 64 power supplies use a different pin for the 5v, earlier versions of this board needed to have wires added to it in order to account for these variants - revision E already has these on the board, so you do not need to add them. See the github page for details on how to modify the earlier revisions of the boards if you already have them.
Commodore 64 Power Saver (Revision E)
*PCBWay community is a sharing platform. We are not responsible for any design issues and parameter issues (board thickness, surface finish, etc.) you choose.
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It's shown in the schematic, more specifically here: https://github.com/tebl/C64-Power-Saver/blob/master/export/C64%20Power%20Saver.pdf
It is hard to tell just from your descript_ion, but I think you may have used wrong values for one or more components (in particular the zener diode is something many get wrong, either direction or value). I recommend hooking it up to an adjustable power supply module, that way you can start at a low voltage and turn it up gradually to see where it flips out.
I got the pcb's and parts from another guy who has built many of them. So I am almost certain that the components are right. The weird thing is that the relay only flips out when I apply a load to it like when I plug the computer in. But not when I apply a voltage to it.
found an answer to my own question , change the value of R2 In my case : 470R = 5.65 V 560R = 5.50 V 610R = 5.45 V 680R = 5.40 V This is in my situation , i tried als 1 M that dropped the treshold to 5.1 or so , that is not really useable. Please measure before and after replacing the R2 with a different value !!
I tried to change the R2 to 680Ohm. In this case, when i plug the saver into the C plus 4, there is no picture, but turns the machine on, and the voltage is dropping to 4.1V (this is less to operate the machine). If i use the original 470Ohm for R2, then, without any load (it is not plugged into the machine yet), the red led is on and the buzzer is loud :) So, i do not know, where is the issue...
I built it as a straight conversion of Ray Carlsens design, just adapting for the parts that I had on hand and what I deemed easy to install and cheap to obtain. For a FET-based design, I recommend that you look at the C64 Saver from bwack (https://github.com/bwack/C64-Saver-bwack).
Thank you for the answer. Both your project and the one you linked seem promising; this time i ordered this one here, i'm waiting for the PCB atm....
Revision E already have these fixes in place though I've not been very good at updating this page for some time, but I did it now so after the updated page is approved by PCBway (in a day or so) you should see the new version (it'll say revision E in the title). If you do not wish to wait you can also grab the gerber-files directly from my github at https://github.com/tebl/C64-Power-Saver.
Revision D was probably directly from the github repository, it has not been tested by me though the changes were mostly moving around some tracks in order to get everything just right. It has come to my attention that some C64 power supplies had 5v on a different pin, this needed a wire on the board - added a notice to the description and updated the repository.
Built a few of the revision D and they should be fine, just needs the extra 5v wire. Checked it out in details and it appears that what I did was reorder the boards to get more of them, but with rev. D on the silkscreen to separate them though no significant changes had been made to them other than cosmetics.
Thank you, as previously commented I've not tested the revision D design and therefore it is not as a shared project. As some wires were simply moved around, I assume the ground plane was disturbed on the second wire. The second one I added to the repository and added a note so that it can be made to work with all surviving power supplies.