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Optimised Power Supply


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Parts list? The few components needed are all there in the schematic. I'm a newcomer to these forums too so I know that it can all be a bit overwhelming at first but you should really take time to read up. If you plan on building a Midibox you really will have to be able to read a simple schematic.

1x cap 2200uF/25V

1x cap 2200uF/16V (+ two extra needed for the last pair of sids)

1x cap 100nF

1x cap 330nF

1x 7809 regulator

1x B40C80 diode bridge (hard to find so replace it with four 1N4001 diodes or any other "strong enough" diode bridge)

Powerplug connector (from a C64)

Powerswitch 2-pole (the one from the C64 works)

Sil headers to connect it with.

If you want a power-led:

1x 220 Ohm resistor

1x Led+socket (from a C64)

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Ok, so I have built my optimised power supply but I have one slightly unusual result. I have followed the scematic but rather than getting 5vdc and 14v DC I get 5v DC and 9v DC.

When I check the output of the bridge rectifier its putting 12v DC out. I have tried 2 different power supplies so I know its not the power supply at fault. Is someone able to tell me the voltage that should be comming directly out of the bridge rectifier before it hits the Caps?

Could the problem be the bridge rectifier dropping the voltage? What should the voltage be out of the bridge rectifier?

I wasnt able to get the B40C80 so I used a 1b4b42, which is 1amp 100v.

Then on to the next point, because Im using a 8580 SID the SID actually requires 9v and my supply is putting out 9.02v then coudlnt I actually just feed that to the SID module as long as I use a 7809 voltage regulator and replace the c1&2 caps with 6,8nF?

Be greatful if someone could help me understaqnd why Im getting 9v rather than 14 and then if I can use the 9v to power the SID module.


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The 5 and 9 volts should add to 14 when wired as per the schematic. How are you checking the voltage? don't be afraid to hook up your modules without the IC's stuffed, and check the power pins for the proper voltage. You could safely use a 7809 on the sid board instead of a 7812, to get the nine volts you need. You may need a heatsink on it (it will be dropping 5 volts as heat). If you are careful you may be able to just use the single 7809 on the optimized psu, but i think the wiring will need to be different, because of the way the 5 and 9 volts are added to get 14, and you wouldn't want to do that to only get 9. If you don't have a clue what I'm talking about, just put the 7809 on the sid module(s) and be done with it. That's what I did on my first sid. (I am using my own powersupply for my MB6582).

Hope I'm not confusing you further.

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Not sure if this helps you too much but I just built my optimized power supply. Everything is working quite nicely on mine! I ordered everything from Mouser in one order and this is my part list:

1 80-C322C334M5U7301 50volts 0.33uF 20% 08/27/08 2 0.670 1.34

2 140-50U5-104M-RC 50V .1uF Y5U 08/27/08 2 0.220 0.44

3 821-TS7809CZ 3-Terminal Fixed 08/27/08 1 0.370 0.37

4 647-UKT1E222MHD 25volt 2200uF 20% 08/27/08 1 1.130 1.13

// Note here you are gonna want to order the 16volt cap as well, I already had one

5 625-W08G-E4 1.5 Amp 800 Volt 08/27/08 1 0.520 0.52

6 625-KBP01M-E4 1.5 Amp 100 Volt 08/27/08 1 0.580 0.58

7 625-DF02MA-E3 1.0 Amp 200 Volt 08/27/08 1 0.380

Notice I ordered a three different bridge rectifiers. I ended up using the first one (number 5) but they should all work. 

I also needed:

- A prototype board to put all this on

- Reused commodore psu connector, switch, and led

- Some pin headers so you can easily connect your psu to you core and sid

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