Transformer help

On Mon, Sep 16, 2013 at 01:21:23AM -0500, Jim Brain wrote: [...] Transformers do not work with DC sources. They're magnetic devices that rely on the primary forming and collapsing a magnetic field in the iron core to induce current in the secondary. However, you can generate AC from DC. In particular, you can just go and buy an inverter that takes 12V (e.g. from a car battery) to generate mains voltages. You can then plug your transformer PSU into that. It's not exactly energy-efficient, but it does the job. You can also skip one of the conversion steps there by using DC-DC converters. There are a number of common COTS parts for these too, although they're relatively simple to build out of discrete components if you want unusual values. Sadly, that doesn't help you generate the same low-voltage AC as the original C64 mains PSU does. Fortunately, you don't usually *need* that. Wikipedia[0] notes: The 9 volt AC is used to supply power via a charge pump to the SID sound generator chip, provide 6.8V via a rectifier to the cassette motor, a "0" pulse for every positive half wave to the time-of-day (TOD) input on the CIA chips, and 9 volts AC directly to the user-port. Thus, as a minimum, a 12 V square wave is required. But a 9 V sine wave is preferred. So you can get away with generating 12V DC and passing it through a transistor that turns it off periodically (e.g. by using a 555 timer to generate 50 or 60Hz) unless you have a user-port device that really does need a sine wave. [0] https://en.wikipedia.org/wiki/Commodore_C64