Re: C-64 PSU

From: Gerrit Heitsch <>
Date: Tue, 24 Apr 2012 16:35:39 +0200
Message-ID: <>
On 04/24/2012 01:01 PM, wrote:
> I recall measuring under (C64) load. Of course it might not have been enough to utilise full output rating of the PSU but it was still noticeably more than 9V. I also recall that problems when I was supplying 9V (also under the same load).

Judging from the circuit inside the C64 that handles the 9V AC, 
supplying exactly 9V should work fine. If it doesn't for you, maybe one 
of the 3 large capactors next to the joystick ports of your C64 is near 
its end.

The old powersupplies give you a bit more since they were designed for 
220V while in most of Europe the voltage is now 230V (+/-10%). I usually 
have 235V at the outlet.

What you could do though is open your old PSU, throw out the old 
rectifier, capacitor and disconnect the regulator (78S05, inside the goo 
around the transformer) and rebuild that part of the PSU:

1) If you can reach the 230V terminals of the transformer, put a small 
switching powersupply that will give you +5V 2A or so in the now free 
space. I used article 350 765 from, fits perfectly. The 
transformer will now only supply the 9V AC.

2) If you can't reach the 230V terminals due to too much goo, put in a 
new rectifier (if the old one was 4 x 1N4001) and capacitor and then use 
a switching regulator for the +5V.

Something like comes to mind. Needs 
to be adjusted to 5.2V so the C64 sees 5V.

Removing the bottom of the power supply is a bit of a pain, but can be 
done with the right tools. If done right, this renovation will leave you 
with a 'new' power supply that looks unchanged from the outside and 
gives you a bit more juice for all your expansion port needs.


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Received on 2012-04-24 15:00:14

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