Sorry, forgot about this thread
Would the wiring you did change for a type B PS section? (Mine will use 5V and 12V)
Nothing. Just use a 7812 in place of the 7809, same wiring
Or would you just split the juice coming in from a 15V DC supply, and use both a PT78ST105 and a PT78ST112? Probably not, as that would split the current too, and 500mA (assuming a 1A supply) prob wouldn't be enough, right? Plus, I'm not sure there would be room for two of those big regulators on the board...
You could, but it would be a bit of a waste of $$ since all you really need is a DC adapter that has enough juice to power the +12V regulator. You can use a linear one (7812)
Ok. Now I'm probably pushing it, but I'll push it.
In my collection of power supplies, I found one from an old Jaz drive. It has DC outputs on 5V/1A and 12V/.75A rails. It's not a grounded plug. Would it be a workable solution to use this? Is that enough ampage? I wouldn't even need regulators on the board, would I? Would that me a safer solution than the C64 brick?
Maybe. If its pretty small its probably a SMPS which may or may not be fine. Test it with load on another circuit and see how it behaves
Yo alti, where did u buy the vreg? And does it really use the same caps as the 78xx vreg? And what kinda heat sink do u use. Please forgive me for not looking too close on the picture, as I am watching from my phone.
If this works and doesn't make switching noise, that's a very nice find! And I want it hehe.
I got it from Mouser. Its a drop in replacement for a 7805 and no heatsink is necessary (it does not really get hot at all). The existing caps for the 5V rail are probably overkill but I left them in anyway. It makes no noise that I can hear at all, it switches at 600 kHz so that is well outside of anything of concern. Here is the doc: http://www.ti.com/li...9a/slts059a.pdf
I have now used this thing in my MBsid, MB808 (which was REALLY bad thermally, 18V input to the 7805 BIG heatsink needed) and my 9090 (which was almost as bad as the MB808, 15V input) and it has worked perfectly in all 3 cases.
I mentioned this in another thread but I'll repeat it here also: These are 85-90% efficient regulators vs 78xx which are about 55% efficient. I did a test to compare the performance of these vs a 78xx by generating a 1.5A load (bank of LEDs) driven by the PT78 and a 78S05 (the 2A one) at varying input voltages. I had no heat sink on the 78S05 and that thing got too hot to touch in seconds at a low input voltage (7.5V) and went into thermal shut down at anything above 12V (and was scary hot). The PT78 was barely warm to the touch at 18V at the input at its maximum load (1.5A). I was sold on these after that
Edited by Altitude, 18 April 2012 - 04:06.