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Ziggy587
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Re: Power Supplies

by Ziggy587 Wed Sep 04, 2019 9:59 am

I can understand replacing the electrolytic capacitor, but is replacing the diodes really necessary? I mean, I know it's a part that can be had for like 10 cents a piece, but still.

Replacing the single cap inside a power brick like this is really easy and a novice shouldn't have much trouble with it, just FYI to anyone who might be considering this.
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Re: Power Supplies

by stickem Wed Sep 04, 2019 10:10 am

^ I've purchased the 3 in 1 sega power supply from the company you linked above. Had it for about a year with no issues. Saves some plug space, doesn't get warm like old power bricks and has worked well for me.
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Re: Power Supplies

by marurun Wed Sep 04, 2019 11:00 am

I don't understand why the various components require their own power supplies. When you attach a PC Engine to a CD or Super CD unit, or a TG-16 to the Turbo CD, you use the power adapter for the CD unit for both, as the console draws power from the CD attachment. But you keep your original power adapter around for funsies, because if you want to detach the CD drive to use as a compact (but not portable) CD player, that's the power adapter you'll want to use.
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Ziggy587
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Re: Power Supplies

by Ziggy587 Wed Sep 04, 2019 12:07 pm

You can mod the Genesis expansion connector to power a Sega CD, apparently it works fine too. You really just need to run power to a single pin.

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http://www.jamma-nation-x.com/jammax/genesismods.html
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Re: Power Supplies

by marurun Wed Sep 04, 2019 12:14 pm

Does that extra power draw create issues for the Sega CD power supply and capacitors?
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Ziggy587
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Re: Power Supplies

by Ziggy587 Wed Sep 04, 2019 12:55 pm

You're drawing power from the Genesis side, not the other way around. But the above mod takes power directly from the DC input. It wouldn't put strain on the console's circuitry, it would put strain on the power adapter for sure though.

edit: "Strain" might not be the best word. If the total power draw of the Genesis and Sega CD is less than what the power adapter is rated for, then there should be no strain I think.
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Re: Power Supplies

by Jagosaurus Wed Sep 04, 2019 1:45 pm

Hopefully this old thread adds some input. I had similar thoughts a few years ago:

Do You Leave Your Retro Consoles/TV Plugged In?
viewtopic.php?f=15&t=48174
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Re: Power Supplies

by Mad_Hatter Wed Sep 04, 2019 5:21 pm

Jagosaurus wrote:Hopefully this old thread adds some input. I had similar thoughts a few years ago:

Do You Leave Your Retro Consoles/TV Plugged In?
viewtopic.php?f=15&t=48174


Being lazy atm... don't feel like reading that atm. What was the general consensus in that thread. Was it considered a fire hazard?

If so, was it only the consoles that had an external power brick?

I'm always worried about my SNES power brick. It's the original one. It can get warm even when the console is turned off.

I can unplug it from the console, but that doesn't stop it from getting warm. It's in a REALLY tight space, so plugging it and unplugging it will be a pain in the arse.
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Re: Power Supplies

by pierrot Wed Sep 04, 2019 6:39 pm

There's a lot going on in this thread right now, and I don't really have time to get into a ton of detail, but I'll try to clear up a few things.


Mad_Hatter wrote:It can get warm even when the console is turned off.

This is normal. Current is always flowing through the primary of a transformer, when it's plugged in. The secondary doesn't conduct until you hit the power on the console. The coils on transformers are just tightly packed bundles of wound wire, and dipoles in the ferrite cores will still shift back and forth with only the primary conducting. Those things result in losses, which generates heat.


marurun wrote:I don't understand why the various components require their own power supplies. When you attach a PC Engine to a CD or Super CD unit, or a TG-16 to the Turbo CD, you use the power adapter for the CD unit for both, as the console draws power from the CD attachment. But you keep your original power adapter around for funsies, because if you want to detach the CD drive to use as a compact (but not portable) CD player, that's the power adapter you'll want to use.

I'm hazarding a guess here, because I don't know the exact reasons for the design decisions, but aside from not having the passthrough connection for the rail voltage at that connector, I'd imagine the PCE/TG16 requires significantly less current to power. One consideration for power delivery is the charge storage elements (capacitors). Especially with DC regulation, where one is trying to keep the voltage near a particular value. In reality, the actual DC voltage falls from the nominal value, the timing of which is based on the time constant: Resistance times capacitance. So the time constant can be increased, and the rate of decay can be slowed by increases capacitance, but this really has more to do with electric charge, and how much charge is required for all of the mosfets to optimally reach their gate threshold voltages. At any rate, if you want more charge, in practice, you often need a bigger (in physical size) capacitor, which comes with a mountain of headaches if you're already space limited.


Ziggy587 wrote:I can understand replacing the electrolytic capacitor, but is replacing the diodes really necessary? I mean, I know it's a part that can be had for like 10 cents a piece, but still.

I didn't look at it in great detail, but I noticed he mentioned cleaning up the power signal for better RGB. Diodes, SCRs, DIAC/TRIACs, etc, are inherently very noisy devices under certain conditions. Zener diodes are often used as ideal noise sources, for instance, when held near their reverse breakdown voltages. Diodes from the 80s were probably worse about their emitted noise. He replaces the ferrite cores also, for probably a similar reason. I would call those unnecessary replacements, but if the object is to clean up noise, it shouldn't hurt, at least.
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