MB6582 Psu option C, a few questions

[asafnetzer]

Hello,

I have failed in obtaining a C64 Psu that fits 220v and would rather use a single 9Vac supply then to buy / build a transformer for Option D.

Was wondering if anyone built his MB6582 with option C Psu and can offer help regarding the wiring and bridging needed.

I understand the wiring between J4 and J74, still trying to figure out what to do with the power socket as the Din socket won't fit with the adapter.

I'm building the MB6582 using the latest pcb and with only 6582 SID's.

Thanks,

Asaf

[Wilba]

"Option C" was a last-minute addition to the base PCB, as a possible workaround - that there IS a place for a 5V regulator and associated capacitors.

Unfortunately, the current requirements of using a single supply (i.e. powering the 5V supply with the 9V supply) might be too much for the regulators, especially the 9V regulator, which will have the entire 5V supply load going through it, in addition to the 9V supply to the SIDs and audio output buffers.

Let's say as a rough estimate, the 5V supply requirement is 1000mA and the 9V supply requirement is 320mA, for 8 SIDs, 4 PICs etc. and a control surface.

The 7805 can handle 1000mA, but if this being supplied by the output of the 7809, then that's 1320mA going through the 7809, which has a rated current limit of 1000mA.

So my suggested solution probably is a bad idea.

It might be better instead to connect the output of the bridge rectifier (J25:9V-11V) to the 7805 input (J74:2) and then the 7805 output (J74:1) goes to the 5V supply (J4:2). However, then you've got another issue, the 7805 will be regulating 1000mA and dissipating heat from a 4V-6V difference between input and output voltages... not too bad, but that will require a serious heatsink and is hardly the most ideal solution.

These are perhaps all worst case numbers, and it might not get that hot...  I don't really know because I have not done this before.

If you do intend on this plan, then if you can find yourself a 1.5A 9V AC adapter, just connect it to the base PCB through the DIN socket by using a DIN plug... i.e. cut off the existing connector on the adapter and solder it to a new plug, or make an adapter (find a female socket for that adapter). J71 and J72 should be bridged as if for PSU Option A.

[asafnetzer]

Thanks for the reply, I would have to consider my steps again.

I was thinking about the current requirements as well, that was one of the reason I've asked about this option.

I thought I've seen the 78XX series in a 1.5A before but I was wrong or looked at another regulator.

With the tight space in the PT10 case I would rather avoid the need of Extra large heatsink.

Thanks for the help,

Asaf

[m00dawg]

One suggestion someone pointed out to me while I was thinking about these ideas myself. If you move all the power stuff outside of the PT-10 case, the only heat being generated that much be of significance would be the SIDs. All other heat would be outside the box and you can deal with it appropriately (big-ass heatsink, metal cage if you want - whatever) and would have the space to do it. That's the route I am going - namely building my own "power brick" to supply 9V and 5V to MB6582 directly. Plus, you can properly fuse the inputs, etc. It's more work, but I'd tend to recommend that option if you don't/can't bother with a C64 PSU.

[asafnetzer]

m00dawg, I'm following your thread very closely and it does look the best option.

I'm still avoiding the need to make my own power supplies and prefer to use a wallwart or an external regulated power supply when possible.

[m00dawg]

Haha I wouldn't call it the best option by any means :) Just another option. Some people really jones for the C64 PSU, some prefer wall-warts - it's all about preference and choice I figure.

[Steev]

Since it looks like Wilba doesn't much recommend the Option C approach, and since the bulk PSU order seems to have hit a snag, has anyone come up with any noob-friendly PSU designs?  For example, could something like the MB-Sid optimized PSU be supplied with separate 9v wall-wart + 5v wall-wart, and the outputs of that supply the 6582? 

And, to get even noobier, what kind of bad things would happen if one were to just hook up a 9v wall-wart and 5v directly to the relevant inputs of the MB-6582 or the MB-SID?  Is it just a little noise or will it blow out the SIDs?  For the MB-SID optimized circuit, my understanding is there is some power conditioning early in the chain of the optimized circuit such that it can take AC and turn it into DC .

Or, let me ask it this way - for those of you who tried Option C, how did it work out?

Sorry for the questions - just one of those "everything you wanted to know about PSUs but you've been too afraid to ask for a few months" questions I've had.

[Futureman]

Mine was a bit different, as I built mine into a keyboard and had a bit of room inside mine (but not enough for a C64 power supply)..

I bought a switchmode power supply that puts out 5vDC & 12vDC (Both regulated)

http://www.jaycar.com.au/productView.asp?ID=MP3108&keywords=switchmode&form=KEYWORD

Although that costed a bit, it's pretty special with delayed switch on / off etc + protection, zero heat etc..

The 5vDC went into the 6582 baseboard as is while the 12vDC goes into the 9V regulator and gets converted to 9VDC.

It works like a charm.

To answer your questions about using two power supplies....  you probably could.. I'm not sure why you would want to? Sooner or later you are going to get a C64 psu right? so why possible risk damaging your SID?

A few things worth noting

-The 5vDC rail does pull a bit of current .. over 1A. (Search 6582 current)

-The 9vDC rail does not pull much.. a few hundred milliamps

-A 9V regulator needs a few more volts than 9V to properly work.. so, in order to make it work, feed it about 12V+

-A 5V regulator is the same, so feed it about 8V DC +

Regards

Mike

[Steev]

Thanks Mike!