C64 Optimized PSU Design Reasoning?

[m00dawg]

So, since I have busted my current C64 power-supply, I've been trying to weigh my options (some including using something other than the C64 PSU). But, while thinking about it, I was wondering - with the C64 Optimized PSU, why is 14VDC being generated and then being regulated down toe 12/9 for each SID board? Would it not be more efficient to step down to 12 and 9 on the optimized PSU board and then simply remove the voltage regulators on the SID boards? I was curious why this was done over the above suggestion. Does it result in a lower signal to noise or something?

In fact, if only newer 8580/6852A SIDs are being used, all that would need to be done when using the C64 PSU is to convert the 9VAC to 9VDC meaning no rectifiers are needed at all?

[Wilba]

You can regulate down to 12 V and/or 9 V with 1A regulators (7812, 7809) and then supply multiple SIDs with a common 12V and/or 9V supply.

And you are right, you can also just rectify and regulate the 9V AC to 9V DC and join it's ground to the 5V/ground, instead of adding the 9V DC to 5V DC to make 14V DC and then regulating that back down to 9V.

I implemented both these ideas on the MB-6582 base PCB and it works fine.

I think the main reason it was done this way is because the SID module has a regulator on it, and for people who want to build just one SID module and one Core, they can supply the SID module with a separate power supply to the one that is powering the Core. Thus the step up to a multi-SID solution is simply to chain the regulator inputs - bypassing the regulators on the SID module and placing them on a separate board might be considered difficult for newbies and more prone to stuffing up and frying SIDs. It happens - when I first started my MB-SID V1 a few years ago, I fried some 6581s by forgetting to put in the 12V regulator and supplying 14V to them :-[

[m00dawg]

Hey thanks Wilba! Glad to hear you've worked through some of these things :) I'm planning on getting some of your MB-6582 boards from Smash but haven't decided if I should keep trudging ahead with my own stuff (since it's fun :) - at least to finish up the small boards I've already been designing.

My other curiosity is if I should try to find an analog power supply that is, say 9V and figure out how to step down from to 5V for CORE. I read some threads on the forum about some people doing that with a series of regulators (but that such things could be noisy) but, after killing my C64 PSU, I realized it's a pain in the ass to find a replacement one of these things over an analog transformer *shrug*

Thanks again for the input!