Alternative powersupply for MB-6582

MIDIbox SID
1

I have a working MB-6582 with 8 sids.

The only problem I have is an anoying noise in the audio signal which I believe is coming from the powersupply.

I only use the 9V sid types so I don’t need 12V.

I used a scope to measure some things an noticed the voltage going in the 7809 voltage regulater is between 10.6V and 11.7V.

I think that’s causing the troubles. 10.6V is simply to low for the voltage regulator to regulate.

I guess my powersupply just can’t handle it and the big capacitors can’t fix that.

So I need a better powersupply. Finding a new commodore 64 power supply is no garantee for a fix so I think a completely different powersupply is a better option.

Is it a good idea to find myself a regulated powersupply which delivers 12V DC and 5V DC?

The 12V DC I can offer directly to the 7809 regulator. All I need to do is bypassing the diodes. I don’t need them anymore since I’m offering a DC voltage directly.

A commodore Amiga 500 powersupply could be an option.

The pinout is here: http://pinouts.ru/Power/amiga500power_pinout.shtml

I notice a 5V, gnd and +12V. There’s also a -12V which I don’t need.

I could solder a different connector to it so it fits the MB-6582.

Is this a good idea or am I missing something here?

2

I have a working MB-6582 with 8 sids.

The only problem I have is an anoying noise in the audio signal which I believe is coming from the powersupply.

I only use the 9V sid types so I don’t need 12V.

I used a scope to measure some things an noticed the voltage going in the 7809 voltage regulater is between 10.6V and 11.7V.

I think that’s causing the troubles. 10.6V is simply to low for the voltage regulator to regulate.

I guess my powersupply just can’t handle it and the big capacitors can’t fix that.

So I need a better powersupply. Finding a new commodore 64 power supply is no garantee for a fix so I think a completely different powersupply is a better option.

Is it a good idea to find myself a regulated powersupply which delivers 12V DC and 5V DC?

The 12V DC I can offer directly to the 7809 regulator. All I need to do is bypassing the diodes. I don’t need them anymore since I’m offering a DC voltage directly.

A commodore Amiga 500 powersupply could be an option.

The pinout is here: http://pinouts.ru/Po…er_pinout.shtml

I notice a 5V, gnd and +12V. There’s also a -12V which I don’t need.

I could solder a different connector to it so it fits the MB-6582.

Is this a good idea or am I missing something here?

You are considering a “switching” power supply.. these regulate by rapidly switching the power on and off, and using an inductor and a cap to smooth the result. Switching supplies offer greater efficiency, less heat, lighter weight, and usually a load of switching noise.

If you’re building an all-digital project then I’d say “Go for it”.. but since you are specifically trying to get a quieter power supply, I’d steer clear of anything with a switcher in it.

Besides, an Amiga somewhere would be without power, and that would be sad indeed. :slight_smile:

The best choice would be to find a transformer that better suits your needs.

Or better yet.. use that scope to look at the OUTPUT of your regulators.. if they are dropping out, it should be obvious.

Good Luck,

LyleHaze

3

You are considering a “switching” power supply..

Don’t know if Commodore used different PSUs over the years, but the Amiga PSU I have is definitely a linear PSU.

S

4

If I were you, I’d go for the C64 power supply, you’re right that it may not cure it, but if you sorted the supply options on the board out, there is a high chance it will.

S

5

I know a commodore 64c powersupply might do the trick, however the mb-6582 is very close to the maximum that the C64 powersupply can handle.

What I like to know if I could offer 12V DC directly to the 7809 regulator on the MB-6582.

The 5V is not the issue. It’s the 7809 that does nog get a high enough voltage to regulate.

So If I get me a power supply with 5V DC and 12V DC I won;t need the big capacitors and the diodes to make the AC into DC. I can offer 12V DC directly to the 7809.

I won’t be needing anything else because I only use the 9V SIDS and not the 12V SIDS.

Is this possible?

6

Yes, it is certainly possible and fairly easy to do provided the mains transformer can offer the power you are after. But I wouldn’t reccomend it for a number of reasons.

One being that if this power supply develops a fault somewhere, you will be without your MB6582 until its fixed.

Given that most MB6582’s already succesfully built use a C64 power supply and they are readily available, it would seem the most obvious choice, if only to try.

If you do decide to build your own supply, please take care with mains voltages.

S

7

I plan on using this “chat approved” PSU:

http://cpc.farnell.com/jsp/search/productdetail.jsp?sku=PW00870

I will be hacking off the 2 pin dc socket (for multiple dc plug sizes that come with it),

and Soldering a 7 pin DIN plug to it, so i can always fall back to a c64 PSU if needs be.

8

Oooof, according to this page the supply is unregelated:

http://cpc.farnell.com/jsp/level5/module.jsp?moduleId=cpc/263667.xml

But isnt the PSU circuit regulated anyway?

Does it matter?

meh

9

Smithy,

both links are AC/AC supplies.

an unregulated DC supply would provide a quite unstable DC that could be stabilized but these just transform the mains voltage into 9VAC or 12VAC.

they will have to be rectified and stabilized first. whether you do it onboard or with externally depends on how you like it / which housing you use.

but besides that i think i remember recommendations for the 5V supply to have at least 1500mA (might be wrong, though)

10

Smithy,

both links are AC/AC supplies.

an unregulated DC supply would provide a quite unstable DC that could be stabilized but these just transform the mains voltage into 9VAC or 12VAC.

they will have to be rectified and stabilized first. whether you do it onboard or with externally depends on how you like it / which housing you use.

but besides that i think i remember recommendations for the 5V supply to have at least 1500mA (might be wrong, though)

9V AC is what you want for MB-6582 Rosch, since its a bridge rectified circuit,

9VDC will not work properly with a rectified circuit.

Its designed to convert AC into DC, so passing DC into this circuit will have a different effect.

“PSU Option C: People could generate 5v from a single unregulated 9v AC supply.”

For the gurus:

From the wiki you get the impression you MUST use Option C if you’re not using a c64 psu.

Why cant you just use Option A with a 9V AC Adapter, that has a 7 Pin DIN Connector soldered to it?

EDIT: Option A uses the 5V DC rail of the C64 PSU also, (as patiently explained by Flemming in the chat. :thumbsup: )

P.S nils and smash said that a 1A rated PSU is more than adequate.

11

cool! thanks for clearing that!

i’m in the process of building my 6582 atm, just with onboard transformer. good to know that 1A will be enough in the 5V section… i really thought i had read that it needs about 1.5A about a year ago… (and about 900mA in the 9V if i remember correctly)

i use separate transformers for 5V & 9V, still have to figure out whether i can do that directly on the base pcb.

edit: i mean just the circuit not the transformers on the pcb

12

cool! thanks for clearing that!

i’m in the process of building my 6582 atm, just with onboard transformer. good to know that 1A will be enough in the 5V section… i really thought i had read that it needs about 1.5A about a year ago… (and about 900mA in the 9V if i remember correctly)

i use separate transformers for 5V & 9V, still have to figure out whether i can do that directly on the base pcb.

edit: i mean just the circuit not the transformers on the pcb

I guess you could use a 7 Pin male DIN connector for the wires coming from both transformers, (just like the plug on the c64)

So you could use a pin for GND, a pin for 5V DC, and 2 pins for 9V AC.

That would it make it backwards compatible with a c64 PSU, as long as the correct pins are used.

13

Oh and btw Rosch, the guys said 1A was adequate by using a 9V AC (Option C) only!

So you *may* need something better rated for the 5V DC line,

at this point id recommend you find out for sure!

14

I use my own custom MB-6582 PSU which is basically some fuses (don’t forget those), a 9VAC transofrmer, some regulators, power resistors, and heatsinks. Not much to it really. I plan on making a nice printed board eventually - just haven’t found a good enclosure to stuff it all in to make everything nice and tidy. Without knowing the enclosure dimensions, printing a board might be wasteful.

When I do get it all finished though, I plan on putting it on the Wiki. On that note, there is some stuff on the Wiki and forum already on how to go about making your own PSU. You have to be careful with mains, yes, but otherwise it’s not really all that difficult. Best part is that you have fuses that blow before your transformer does. The C64 PSU sucks. Anyone who says otherwise must enjoy some bit of masochism or has never had to figure out how to open it up, dig through a mountain of epoxy just to get to the fuse that’s probably blown. No thanks. Besides, making your own PSU is hella more fun :slight_smile:

Just my $0.02

15

I meassured the current draw of my MB6582 when it was idle and it used allmost exaclty 1A so I’d recommend 1.5A supply to have some headroom. I use a C64 power supply, but plan to build a power supply box (containing VCFs, VCAs and PSU) feeding 12V dc + gnd into the ac input of the MB6582. Are there any objections to this?

16

I had some noise with the C64 power supply, I had repaired it with a smaller capacitor than the default and the ripple voltage was audible. While waiting for a bigger capacitor, I took a 9V AC transformer power supply (31VA) and combined it with a 5V switching power supply (2.3A) that I had laying around and a 9-pin DIN connector and it worked fine.

17

I had some noise with the C64 power supply, I had repaired it with a smaller capacitor than the default and the ripple voltage was audible. While waiting for a bigger capacitor, I took a 9V AC transformer power supply (31VA) and combined it with a 5V switching power supply (2.3A) that I had laying around and a 9-pin DIN connector and it worked fine.

Good to know.

18

I have a similar problem using option A. on my 6582.

It’s got quite a loud hum associated with it, which is a bit irritating.

It can be masked up by the big fat sounds, but the more delicate tones always have BZZZZZZZ in the background.

One time it did disappear, but I have no idea how I did it.

Has anyone figured a solution for the C64 psu noise issue?

I’m using a green cap on C2 as I didn’t have any monolithic caps available in that value.

Could that be the problem?

19

I measured the output from the psu and regulator.

Once everything was plugged in and I’m getting a few percent less voltage than normal.

Could this be the source of my Hum?

Is the regulator not getting enough juice to run efficiently?

Maybe I should re-populate the PSU section for another option?

Sooo close to finished I can taste it!

20

Sry for late posting, but MissionBrown, could you take out a few of your SIDs if you have more than two? Still humming? Did you ground the SID audio inputs with a jumper?

I have three C64 power supplies by now (using ebay to harvest old c64s and they usually come with power supplies) - and all provide good power and there is no humming.

But i only have three 8580s populated so far (PSU option A). I don´t even use the condensator at C2 in the PSU section, because i accidently broke it while building the mainboard (the spare shipment is expected to arrive tomorrow).

If you really want a different power supply than the original C64, go for it. But I can assure you, at least with only a few SIDs populated, these power supplies are perfect (three out of three tested) and very calm.