technobreath Posted January 24, 2011 Report Share Posted January 24, 2011 Hi, Designing a powersupply for mb6582, and I was wondering if anyone had a good answer to how much current the 5 volt rails on an mb6582 draws. The design assumes red 3mm LEDs with 220ohm resistor, other than that - a full stuffed CS with a black background and red character 4x20 LCD. I'm trying to figure out what transformer to use for the 5v rail. If anyone of you have a good idea on how much it draws, or even better if you have a mb6582 and is able to measure it for me, I would appreciate it. Thanks. Quote Link to comment Share on other sites More sharing options...
Hawkeye Posted January 24, 2011 Report Share Posted January 24, 2011 (edited) Quoting Wilba: Based on datasheet calculations, the 5V supply usage is ~1000mA. PICs are 23mA each, 6582A SIDs 70/100mA each, LEDs 100mA max, LCD ~280mA. If the SIDs are at the max current, then it's ~1200mA. 9V supply usage is ~320mA 2A if you want to be safe - the 1.x amps from the original c64 psu work fine. Beware of switching PSUs, as they may add noise to your analog audio path, the old-school linear original C64 psu is not a bad choice at least regarding noise. Edited January 24, 2011 by Hawkeye Quote Link to comment Share on other sites More sharing options...
Shuriken Posted January 24, 2011 Report Share Posted January 24, 2011 (edited) Quoting Wilba: 2A if you want to be safe - the 1.x amps from the original c64 psu work fine. Beware of switching PSUs, as they may add noise to your analog audio path, the old-school linear original C64 psu is not a bad choice at least regarding noise. 1.7 amps on the c64c(II) brick. But i will go for 2 amps. Edited January 24, 2011 by Shuriken Quote Link to comment Share on other sites More sharing options...
technobreath Posted January 24, 2011 Author Report Share Posted January 24, 2011 (edited) hawk, the original c64 psu is way too easily broken, so that is why I (adviced from nils and company) build my own psu :). I am not sure I get the quote from wilba. There is talk about 320mA for the 9v rail, but if each 8580 (6582) draws max 100mA (and typical) 70, then the correct rating for the 9V rating should be above 800mA just for the SIDs - assuming you want to have the possibility to stuff all 8 of them with 8580s. - According to datasheets the mA ratings for the 6581 is just the same - max 100mA each for the 12V. As I understood it, the only thing in the box that runs of the 12v and 9v is SIDs with their output cuircut - that is a little < 1000mA with 8 SIDs stuffed. And that is for the 12 and 9V rails. As for the 5V rail all the rest (core modules, leds and LCD roughly counted together) should run off this - and not use the 12 or 9 volt. So, PICs, LEDs and LCD should draw about 564mA assuming the above quote is correct, so my conclusion from the info you provided is: 1000mA for each voltage rail (12, 9 and 5 volt) should be more than enough... Sounds about right, or am I way off?? :) EDIT: Don't worry about me using a switched psu... that's not gonna happen. I don't build such a rare nice synth just to make it sound baaaad. :D My goal here is to calculate the most reasonable ratings I need for my transformers in the PSU. Edited January 24, 2011 by technobreath Quote Link to comment Share on other sites More sharing options...
phunk Posted January 24, 2011 Report Share Posted January 24, 2011 erm..a standard LED (assuming you use standard LEDs) draws about 20mA. How many are in a MB6582? Even though not all are lit at the same time i´d calculate more than 100mA. Quote Link to comment Share on other sites More sharing options...
technobreath Posted January 24, 2011 Author Report Share Posted January 24, 2011 (edited) Hi phunk. As you see, I have calculated from 560mA or so for the 5V rail up to 1000mA... should be enough...? EDIT: My problem is neither space or heat as this is an external rackmount style psu I'm planning. As long as the components are stable enough in the heat they generate. So it doesn't matter if I build it for max 500mA or 1000mA or 2000mA for that matter... :) Edited January 24, 2011 by technobreath Quote Link to comment Share on other sites More sharing options...
Shuriken Posted January 24, 2011 Report Share Posted January 24, 2011 And i am sure you are wrong on the SIDs as well. If you check the Sammich build guide or http://www.ucapps.de/mbhp_sid.html the SIDS use both 9V and 5V or 12V and 5V. I am desinging my own psu aswell. Since people have problems with the C64 PSU i figured 1A on the 9V and 2A on the 5V would be on the safe side. Quote Link to comment Share on other sites More sharing options...
technobreath Posted January 24, 2011 Author Report Share Posted January 24, 2011 My misstake... the sids use 5 volt too. Forgotten. I have the datasheets, so calculating wont be a problem. What i was looking for here was the current draw from everything but the sid modules, but thanks for pointing that out. If the core8 and lcd from the wilba quote is correct i will just have to redo my calculations taking the real current draw from leds pluss the 5 volt currentdraw for sids into account and ill have the specs. Its no point for me making a psu based on assumptions on current draw as nils told me also, because then i wont actually learn anything. Its cool to know how to calc every step of the specs, not just overdo it and assume its ok. Im sure it would be ok to do that also, but what i have learnt these days is that its more to psu design than just follow some general recomendations, its much more usefull to know every step for the next psu im gonna build. Then i can build it by reading datasheets instead of bugging you guys with same questions all over again. Quote Link to comment Share on other sites More sharing options...
Hawkeye Posted January 24, 2011 Report Share Posted January 24, 2011 (edited) I understand the fear of fried sids and also have an uneasy feeling about using the aged standard power brick... On the other hand, I´ve used c64s for 25 years now (some years more frequently, some years less frequently, but there was no single year when i did not use it - katakis and chris huelsbeck rule) and i must say that during that lifespan i never had a faulty PSU, the worst thing that happened to me was a fried 6566 (video) chip. Edited January 24, 2011 by Hawkeye Quote Link to comment Share on other sites More sharing options...
technobreath Posted January 24, 2011 Author Report Share Posted January 24, 2011 yeah, I've also been using the c64 often enough with no personal experience of psu fail... but it seems its more common than our experience with it, so - I will not take the risk of blowing a psu, and maybe take the mb6582 with it in the fall. :) Quote Link to comment Share on other sites More sharing options...
Shuriken Posted January 25, 2011 Report Share Posted January 25, 2011 As i am still in the process of making my own. I am curious to know what kind of Power Regulators you are planning to use? I was thinking of using 78S05 and 7809. Quote Link to comment Share on other sites More sharing options...
nILS Posted January 25, 2011 Report Share Posted January 25, 2011 As for the 5V regulator I'd suggest a 7805K in TO-3. Quote Link to comment Share on other sites More sharing options...
nebula Posted January 26, 2011 Report Share Posted January 26, 2011 You shouldn't need to regulate the 9 volt output. On the original C64 power supply, 9VAC is provided directly from the transformer. I have also been pondering building a power supply, starting with a hammond trafo with dual 9V windings. One winding would go directly to the 9V input, the other would be regulated to 5VDC using a standard linear circuit built around a 78S05. FWIW I used to have 3 working C64 power supplies, and now I have one. Two of them popped while powering up my MB-6582 (with 8x 6582). So a new, beefier, serviceable power supply seems like just the ticket. I don't know whether to simply build a C64 power supply, or go a step further and put in a housing alongside Seppo's modules (AOUT_NG, SSM2044, VCA), and maybe an audio mixer, plus the required power for all that. The whole thing could connect to the MB-6582 via the DB25 expansion port, which would really tidy things up! Quote Link to comment Share on other sites More sharing options...
Shuriken Posted January 26, 2011 Report Share Posted January 26, 2011 (edited) As for the 5V regulator I'd suggest a 7805K in TO-3. That's still only 1A. The 78S05 can do 2A. You shouldn't need to regulate the 9 volt output. On the original C64 power supply, 9VAC is provided directly from the transformer. I have also been pondering building a power supply, starting with a hammond trafo with dual 9V windings. One winding would go directly to the 9V input, the other would be regulated to 5VDC using a standard linear circuit built around a 78S05. FWIW I used to have 3 working C64 power supplies, and now I have one. Two of them popped while powering up my MB-6582 (with 8x 6582). So a new, beefier, serviceable power supply seems like just the ticket. I don't know whether to simply build a C64 power supply, or go a step further and put in a housing alongside Seppo's modules (AOUT_NG, SSM2044, VCA), and maybe an audio mixer, plus the required power for all that. The whole thing could connect to the MB-6582 via the DB25 expansion port, which would really tidy things up! That would be the case if i had a 7809 inside the MB6582. I figured why put an additional heatsource inside the box? Edited January 26, 2011 by Shuriken Quote Link to comment Share on other sites More sharing options...
nebula Posted January 26, 2011 Report Share Posted January 26, 2011 That's still only 1A. The 78S05 can do 2A. If you look hard enough you'll find 2A and 3A 7805 variants in TO-3 cases. TO-3 dissipates heat much better than TO-220. That would be the case if i had a 7809 inside the MB6582. I figured why put an additional heatsource inside the box? Well, there's really not that much heat in the box ... I guess I like the idea of the MB-6582 power supply being interchangeable with a C64. YMMV Quote Link to comment Share on other sites More sharing options...
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