technobreath

Hi. Strophlex, did you make the wiki on the psu? Nice work, however a few comments after reading through. In the centertap xformer chapter there is some minor stuff that seems not to be correct. It says that 15v transformer is needed because of voltage drop over the rectifier. If one uses a fullbridge rectifier, 4 diodes, this isnt completely correct. Rectfied voltage will be higher than ac, so a formula is needed to calculate the exact output from the rectifier. The reason that you need headroom is because of the vdrop over the vreg. I know this is details, but if you document a design so good it might as well be correct, no offence at all. The transformer's ac out should be calculated as close as possible to what dc the vregs need, taking into account the higher voltage on the dc side of the rectifier. Also the vregs datasheet tell u what headroom voltage it needs. It aint always true that it needs 3 volts. The input volt range of the vregs tell you what it can take, but beware of the extra heat genetated in the vreg if it has much headroom voltage. Best is to calculate everything as close to ideal as possible taking into account the worst case scenarios such as variations in mains voltage etc. Also one last thing. Psu design isnt just about getting the right voltage out of it. The design in the wiki offer no protections from over voltage or excessive current draw. It needs to be protected itself, and to protect the load also from a short in the psu. A fuse is not enough by long shot. You need some way to eat power in the psu while giving the fuse time to blow. If only a fuse is used it is most likley to kill a lot when there is a fault somewhere before it blows. A way to think of fuses is that they are only there to cut power when spmething fails, the actual fast and real protection are in the electronics. I would never run a mb6582 without this real protection. The c64 psu design isnt ideal at all for the synth. It has as mentioned a tendency to fail and take sids and other precious stuff with it. Maby use them with success, but i wouldt do it. Just my thoughts... not meaning to offend any in any way. Tbreath

Thanks Alex for your huge efforts :) The raised price doesn't exactly make a huge impact :) At least for my 50 knobs it won't make very much difference - I just drop the coke and hotdog for lunch tomorrow and it will be settled :P Any new time frame on the process? When do you plan to place the order?

About postage prices and customs. It is just a few bucks. My thoughts: One guy in germany order a huge box from Tim. Pay everything. Now he's gotta find out how much each and everyone ows in customs and postage. Then he gotta take some money for the redistrubution job in germany. All in all, it's better going to work a couple of hours overtime, and then buy what you need instead of using a lot of time and energy trying to save a few bucks on postage... IMHO. For the record, I will recommend dealing with smashTV any time. He has extremely fair prices, you get what you order, and you get it in good package and great condition. The attitude is service. And by shopping from him you will also help keep the community alive in some way... not that it's near death or anything :) You get the idea...

Hi. I have been looking for a good supplier for transformers, i will look into digikey's ones. That psu schematic you link to i havent seen before, but it will not be good enough as a full featured custom psu for the mb6582 i think. It has no 12v wich is required for 6581 sids. You will also have to depend on more circuits inside the synth to work. Also i cant see its regulated in any way and as far as i can see it has no other overcurrent protection than regular fuses. I guess if this actually is a real diagram for the c64 psu some protecting circuit is designed into the c64 itself. This design differs a lot from my design and cant be used for what i plan, but it may very well work for some boxes. I havent studied thw different psu options for the synth well enough to say if this is good enough... Let us know how it works out with this solution and good luck :-) Ill post a pic of my circuit later on when i figure out how to design the current limiter. Its almost finished now. If more. people are interested in the psu i should maybe try to design it with that in mind - easily available parts and a good pcb design etc... I have no real experience with routing pcbs other than by hand with permanent marker hehe, so i should get myself a descent program for this and make a pcb design. What program do we midiboxers use for this? I could do it in ultiroute, but it aint free and i suspect most midiboxers would prefer a free alternative... ive seen there is a prog - eagle - can this be used for this? Tbreath

What is the specs on the transformer(s) you use? Hehe, u cant run vregs off mains hehe. 78xx vregs get very hot at those currents... glad it works for you. And its nice to hear that the synth doesnt require extreme amount of power to work. My idea is however to make a psu wich will go on and on under worst condotions. And for that i need to design a way to blow fuses in a safe way. Hence the current limiting transistor. Fuses blow too slow to protect against the shorts from the load, and the current limiter buys time for the fuse to blow before you destroy the pass transistor, vregs or the tansformer. The idea is for powersupply protection in case the synth fails and tries to draw too much current through the psu. Also when it does so it shuts down (blow the fuse) and protect the load from further damage. A design with vregs only works as you have prooven with proper heat sinks, but if anything fails, u will most likely end up fixing the psu as well as the synth. With current limiting based on transistor you will be as safe as u can be. A crowbar circuit may also be used instead of transistor limiter, hands up for smashtv for that tip. Star: sorry for kinda hijacking your thread. It wasnt my purpose. I only meant to give u guys a heads up that im working on what you asked for right now... hope you get some info that is valuable to you from it. For my blog: where is a good place to host pics online wich doesnt get deleted after only a short time? Any suggestions? Preferably a free host that is... Tbreath

Hello. Im in the process of designing this powersupply. I have both sids type, so the powersupply will have 5 volt max 5amp and 9 and 12volt max 1 amp each. I have a pretty good start on the design and a pretty good idea on how its gonna be. Due to insufficient funds at the end of this month, i havent yet ordered in the transformers and i also lack some caps, but from feb 5th i will start some serious work on prototyping. I will post every bit of info on this when its ready. So far the design features 3 transformers, one at 17vac for 12v dc regulated, 9vac for 9vdc regulated and 9vac for 5vdc regulated. The choice of sec. output voltage is based on calculations of how much the voltage is increased passing the rectifier bridge, availability of transformers and some headroom. Each transformer will be followed by a rect.bridge of their own. The 12 and 9 volt rails will be driven from a 2amp max 78xx (L78S09C and L78S12C if my memory is intact). The 5 volt rail will be driven from a regular 7805 and a 5amp max pass transistor or what its called, for higher current. This way the high current transistor will take on most of the load, enabling the psu to pump 5amps max to the mb6582s 5volt system. Based on calculations and experience of people who built the synth, no more than 2amps is required for 5volt, but i want to have this headroom because 1: i want to be sure it works under worst conditions like more enviormental heat than normal. The datasheet for the transistor i have in mind (tip122) states temp test condition to 25c. 2: i might find out that i want to drive more cuircuts from the same psu like midibox64e or midiboxLC for a live controller for vsti i use in addition to the sid. Because of this i will provide a extra 5 volt output from the psu for this use in addition to a output plug with all three voltages for the mb6582. The outputs will require some kind of transistor based current limitors to make sure the psu's outputs are protected. My plan is to protect the 9 and 12volt rails on 1 amp each. The 5 volt for sidsynth will be limited to 3 amps and the extra 5volt output limited on 1,5 amps. Each rail will have 25v 2k to 4k uF caps after the rect.bridges. also additional caps are required around the vregs as stated in their datasheets. A good referance is TKs core8 psu schematics for caps needed. The psu i design is meant to fit in a 19" rack. I have not yet taken the space needed for the components into account, but i take it for granted they will fit in my 3 unit box from an old pa amp i am going to gut. This psu will require serious heat sinking for output transistors an also for the vregs. Personally i will install a fan too. So that is about my plans for the design. I will make a work blog or something with details and pics when i start prototyping next month. Tbreath.

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. :)

No rush phunk. Ur work is heavily appreciated. I think its non-prp of them to promise and not follow through though. It would be better to just explain the situation right away and maybe give a timeframe that they could manage to keep...

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.

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... :)

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.

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.

Sorry to hear about this! I most likly will not be finding it since I am in norway, but one thing I thought of - does the mb6582 have any serial numeber printed on it or anything else that makes it totally unique? It would be easier to identify if someone sees it on ebay or similar... one could ask the seller also...

Hehe, I really like that bad beer line :). It might be that vodka goes well, but I won't get some now. In my younger years I drank way too much once, and I can't even stand the smell of it now :) Same goes for whisky, but beer I love :) Not too dark though... :)

:D EDIT: I actually had to google "scnr" Haha. Am I getting old? :P

Hi! This is not very hard to google when you need it, and I'm sure someone has already posted similar here before, but I have used this website a lot while building my projects, and thought I would just share it with you guys in case someone hasn't thought of this. All who want should have the joy of a tool like this: http://www.dannyg.com/examples/res2/resistor.htm I think it's a very nice tool and it's easy to use and read results both graphical and text.

Btw what is the minimun?

I have had several multimeters in all price ranges and i have never seen one wo the beeping function, strange... I just bought a fluke for my job, and it turned out to limit on 1k wich was bad, because i need to measure in the range from 0 to 10k as i work with alarmsystems. Big misstake, so if u buy a new multimeter then make sure it does what u need hehe. I discovered this after writing my name all over it, so no chance of returning it hehe, and it wasnt cheap! About 100 euros.