MB-6582 DIY C64 Power Supply replacement

[Blatboy]

I've gone through and read most everything I could find about power supplies in the forums here. (Including the )  Outside of the fact that my brain is melting onto the keyboard as I type right now, I think I have a gist.   I'd like to try to summarize here to be sure I'm on the right track, and I also have a couple questions. 

 

My MB-6582 has PSU option B.  I have all 8580s... I do have a couple 6581s but I don't have plans on using them.

 

I'll be assembling this supply as a project in a class I'm taking.  This week I'll need to decide between linear and switching designs and then order parts.  If I did a linear supply, I'd use and put it in a plastic case.  All this makes sense to me.  It's just a matter of doing a good, compact, well heat-sinked physical design...and finding the right transformer.  I'm having difficulty finding a 120V primary to 2 X 9V secondary transformer...

 

Being that I plan on using my MB-6582 for live gigs, portability is a concern...I'm intrigued by the idea of a smaller, lighter PSU.  So, I'm looking at the switching options.  The Meanwell RPT-60B looks like a one stop simple solution.  Just to be sure I understand correctly... even though the 2nd output is plus/minus 12VDC, it's ok to use those in the 9VAC input?  I saw some other designs with circuitry after the RPD-60B.  Would that be necessary?  

 

Lastly, regarding the connection to the MB-6582 itself from the new power supply... outside of sacrificing an old C64 PSU for it's cable and connector, (which I don't have an extra... why did I throw that old one out?)  what kind of cable do I get?  The connection is 7 pin din, but only 4 of the pins are used, yes?  Or, in the end, is it just better to get another old C64 PSU (hopefully not working, to save the buck) and cut the cable?

 

Thanks so much for any thoughts!  I know this subject has been rehashed many times...

[Blatboy]

...and, regarding that transformer... If I can't find one with two 9V secondaries, would it be ok to just do both rails off of one 120V/9V transformer?  Using two transformers looks like it'll be really heavy.    Even just a single 9V transformer isn't small...  

 

Ooooooh.  Actually, I think I found a dual output transformer.... would this:

 

http://www.mouser.com/ProductDetail/Triad-Magnetics/VPT18-1390/?qs=sGAEpiMZZMvwUzoUXIIvyTw34uqMHR%252buJampnWcUvS4%3d

 

solve my dilemma?

[Altitude]

Not sure why you keep insisting on having a 9VAC rail, there is nothing you need to power with an AC source, it's rectified to DC anyway and was only built into the design since the C64 PSU only has 9VAC and 5VDC power and those needed to be combined to get the 14+VDC needed for the 12VDC vRegs. You can use a 12VDC switching wall wart and not have to deal with transformers or mains voltages at all.  A fully stuffed MB6582 draws just over an amp using a 12VDC adapter, going to some crazy 5A switching device with 3 outputs is a waste of time and money.  I use the Triad 1.5A switching wall warts they have at mouser and one of those plus a swtiching 5V reg for the digital side will run you all of $25

 

Besides, 9VAC isn't enough to power the device anyway on its own since there is a 1.4V voltage drop across the bridge rectifier and you need a 2V overhead for a 7809

[Blatboy]

That's the part I didn't quite 100% understand, but I guess I did read that right then.  So, it is ok to put 12VDC in the 9VAC rails.   But, the C64 supply works, yes?  It supplies only 9VAC to the 7809 on the control board, yes?   

 

If I was to use wall warts... did you just snip off the plugs at the end and hook it up to a 7 pin din connector?  Do you have a picture of yours?  I'd love to see how you set it up.  Even if it's not fancy, PM me a shot, if that's ok.    I just checked out your pictures.  OMG your SEQv4 w/the BLM is freakin' incredible.  I need a cigarette after just seeing that.  Jeez. 

 

Ahem.  Back to the power supply...  I know it's not the easiest nor the most cost effective to go with a linear design.  I do need a project for my class, and the wall warts, while certainly the most direct route, may not be beefy enough for the project.  (Yeah, I know... pick another project.  I'm not that creative.)  We'll see though.  I may make a linear one to keep in the studio and just use you wall wart setup on live gigs.  Less to carry.

Edited October 18, 2014 by Blatboy

[latigid on]

Alt, do you mean 1 amp draw for a regular MB-6582 or with your switching solution? I am using your recommended 5 V switching voltage regulator (http://www.mouser.ch/ProductDetail/Texas-Instruments/78SR105HC/?qs=sGAEpiMZZMtwaiKVUtQsNWWYJJUUxYbPRFCRyYymPj0%3D) where I am drawing about 200 mA with all LEDs lit. This is without SIDs so far, hopefully this weekend!

 

I found the back was a better place to mount it, this way the 7809 can heatsink on the huge ground plane. This works better for the 5 V pinout too, where the (redundant?) smaller smoothing caps are now on the output.

 

 

 

 

 

To Blatboy: as Wilba designed this with a C64 brick in mind, you have to solder a few jumper wires to get the power in off a single supply. You can for instance use the DIN7 socket and forgo redesigning the back panel. Check this thread for Altitude's work:

 

 

 

 

Just a note: your rectified 9 VAC will actually be near to 12.6 VDC once smoothed out.

 

9 VAC * 1.4   = 12.6 VDC  rectifying and smoothing
12.6  - 2*0.7 = 11.2 VDC  two diode drops

Should be enough for a 7809.

 

Edited October 18, 2014 by latigid on

[Blatboy]

Thanks for the link.  I remembered that thread but couldn't for the life of me find it again.

 

I guess the idea of having one supply (linear) for the studio and one for gigs doesn't really work I need to bypass the rectifier for one and not the other.

 

Hmmm.  Unless I put the rectifier in the external linear supply so that both solutions bring in 12VDC.

 

Yeah.  I'm probably getting stupidly crazy with this.  I should probably do what altitude did, regardless of my class project situation.  If it ain't fixed, don't break it!!  uh.... or something like that.

Edited October 18, 2014 by Blatboy

[Blatboy]

That TI DC to DC converter is obsolete and unavailable...  

 

This should do, yes?

 

http://www.mouser.com/ProductDetail/RECOM-Power/R-78B50-15/?qs=sGAEpiMZZMuur7c7MCGU2MKVsZpEbW5x

[latigid on]

You can put anything through a recitifier (AC or DC) but you have to deal with the diode drop in both cases. Study the PCB layout on the wiki and draw a circuit diagram for a start. Also keep in mind that several of the pins in the DIN connector are not used... If you're serious (and crazy) about using two separate supplies there's nothing stopping you having two different configurations wired to separate pins of the socket.

[Altitude]

 

 

Alt, do you mean 1 amp draw for a regular MB-6582 or with your switching solution? I am using your recommended 5 V switching voltage regulator (http://www.mouser.ch/ProductDetail/Texas-Instruments/78SR105HC/?qs=sGAEpiMZZMtwaiKVUtQsNWWYJJUUxYbPRFCRyYymPj0%3D) where I am drawing about 200 mA with all LEDs lit. This is without SIDs so far, hopefully this weekend

 

 

 

That sounds about right.  The SIDs draw crazy power, close to 800 mA on my rig

 

as far as running on 9VAC, 11.4 is really pushing it since you should always factor in 10% variability on the mains, I always give it 2.5V overhead

 

 

That's the part I didn't quite 100% understand, but I guess I did read that right then.  So, it is ok to put 12VDC in the 9VAC rails.   But, the C64 supply works, yes?

 

Yes but you will get a 1.4V drop across the bridge rectifier though and that wont be enough for a 7809 (10.4V)

 

 

  It supplies only 9VAC to the 7809 on the control board, yes? 

 

No.  The 9VAC is rectified and smoothed providing ~11.4VDC to the 7809 .  You cannot run a 7809 off an AC voltage, it has to be a (well) smoothed DC voltage.  You would still need to rewire the PSU (PSU option C) to generate the +5 rail off that 11.4VDC which then begs the question of why not just pull the bridge rectifier and use a modern compact 12VDC adapter, a 1.5A one will be a fraction of the weight and size of a 1.5A 9VAC one.  Either way, you will need a way to deal with the heat from the 5V vReg (use a switcher).  The ONLY reason the 9VAC made ANY sense was when generated by the C64 PSU which already had a regulated 5VDC output

 

 

You dont need the 1.5A Recom, the 500 mA ($3) one is fine, the SIDs draw 80% of the current

Edited October 18, 2014 by Altitude

[Blatboy]

 

No.  The 9VAC is rectified and smoothed providing ~11.4VDC to the 7809 .  You cannot run a 7809 off an AC voltage, it has to be a (well) smoothed DC voltage.  

 

Ugh.  I knew this, yet wasn't thinking, obviously.   Sorry.

 

 

You dont need the 1.5A Recom, the 500 mA ($3) one is fine, the SIDs draw 80% of the current

 

 

Awesome.  Thanks.   

 

I really appreciate you guys taking the time to answer my (sometimes ill-thought) questions.  

 

I'll do a switching supply.  I have other things to fix on my unit as it is...I'm sure that's enough to make a "project" out of this.

[Blatboy]

Holy jehosaphatt!

 

This solution is so incredible.  Originally I was thinking about spending $60-100 bucks on a box I'd have to build and carry around.  Now that I've re-read Altitude's original post (for the 50th time probably, but I think it finally got through my thick freakin' skull) I get it.  And here I am about to spend $15-$35 on parts and barely anything to build.  I'm going to get crazy and get TWO wall warts...  one for the studio and one for the gig bag.

 

This regulator:

 

http://www.mouser.com/Search/ProductDetail.aspx?R=R-78E5.0-0.5virtualkey56830000virtualkey919-R-78E5.0-0.5

 

and this wall wart:

 

http://www.mouser.com/Search/ProductDetail.aspx?R=WSU120-1500-Rvirtualkey55310000virtualkey553-WSU120-1500-R

 

and, if I want a connector...this guy...

 

http://www.mouser.com/Search/ProductDetail.aspx?R=C091_31H007_100_2virtualkey52360000virtualkey523-C09131H0071002

 

Hook up the wall wart to the pins that were originally the AC pins... take out the rectifier... do that one jumper wire on the bottom of the base board... and I'm good to go, right?

 

So simple.  

Edited October 19, 2014 by Blatboy

[Shuriken]

I don't think that regulator will be able to power the whole box. It's only 0,5A. I would recommend getting the 1.0A version (http://www.mouser.de/ProductDetail/RECOM-Power/R-78C50-10/?qs=sGAEpiMZZMt6Q9lZSPl3RYmx3feB3IQNN76eLdDNaE8%3d)

[Altitude]

Yeah, 1A is probably a better idea.

 

Dont bother with that expensive connector, use this one instead:

 

http://www.mouser.com/ProductDetail/REAN-Neutrik/NYS323G/?qs=sGAEpiMZZMvf6myxbP4FpHeA2rMiar4t9tRsaFKojIY%3d

[Blatboy]

Thanks for the help on that.   Hmmm.  Sometimes the parametric search doesn't always come up with the best parts.  Don't know how I missed the cheap connector, perhaps I'm not doing it the best way.  I'm glad you pointed it out.

 

I made the adjustments to the order and sent it in.  Thanks again.

[Blatboy]

So, I've installed everything... also changed my power supply to a type, and used Altitude's post as a guide.  

 

So far, things seem to be working like a charm.  I'll put it though more rigorous testing later this week.

 

Thanks for the help!