On Tue, Nov 9, 2021 at 8:19 AM tokafondo_at_gmail.com <tokafondo@gmail.com> wrote: > > > So, speaking, a transformer that with a 4A AC 11,5V secondary will be just too much. you have to measure the AC voltage under load, let's say around 1A load will give you the right idea about the loaded voltage. The older C64 boards, the ones we usually found in the breadbin cases, use this AC input (among other things) to obtain the 12V and 5V DC rails used by the SID and VIC-II chips. The regulators are standard LM78xx 1A TO-220 ones. The 12V regulator is not heatsinked, the 5V regulator has a quite underrated heatsink. Feeding more than 9V AC is not only unnecessary, but it would increase the power wasted (turned into heat) into the two regulators. The DC input to the regulators will be close to the AC voltage times 1.41 (square root of 2 approximated). I've always been able to find the 9VAC (loaded) transformers easily. You need 18-22VA ones, anything bigger is not necessary.h The newer C64C boards usually can tolerate a higher AC voltage without problems, but it's still better to remain in the right ballpark. HTH Frank IZ8DWF > > ------ Mensaje original------ > De: tokafondo_at_gmail.com > Fecha: lun., 8 nov. 2021 22:23 > Para: cbm-hackers_at_musoftware.de; > CC: > Asunto:Max AC input in C64 > > I'm finding difficult to get a proper 9v transformer for my c64. > > They say that there is a tolerance in that input, because the internal circuitry will compensate higher and lower voltage. > > Anyone knows about this tolerance? > > Thanks. >Received on 2021-11-09 11:00:03
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