What's the best console power supply?

[Syntax]

I was wondering what is the best linear power supply available for consoles?

I'm using a Mega Drive 1 PSU at the moment.
They only really have 3 components, a transformer a resistor and a 3300uf 16v cap. There's space for another cap so I replaced the 3300uf with 2 2200uf.

It's a reliable supply of 12-14v but I'm sure there's something else cleaner that I can use as a control when modding systems.

[ASDR]

Pretty sure there's a rectifier or at least a diode for a half-wave one in there as well as it outputs DC? I also have a few MD1 PSUs for my replacement PSU needs. They're great and readily available. I don't think there's a big difference between linear PSUs. As long as the capacitor is large enough, what's the difference for the console? The voltage regulator should be able to get rid of the ripple. The differences between SMPS are much larger as the voltage regular can't reject the high frequency noise and old consoles designed for linear PSUs likely don't contain any additional power filtering. Everything except the rare grounded or very well build SMPS has significant AC leakage, but I don't think you're going to get any variation in audio/video/stability when switching between any reasonable set of linear PSUs.

I also have an old linear bench PSU. Only does CV, analog voltage display. I doubt they're being sold anymore, but if you can find any on eBay they're useful to have around. It's a good sanity check if you suspect the PSU to be an issue and you want to have a linear one.

[Syntax]

Yeah the a bridge rectifier in there but I didn't mention it as it doesn't really change noise levels just a safety measure.

Is there anything else I can add to the circuit to better clean the power? A 100n decoupling is pointless that far from the console right? But I was thinking a 10-100uf may help the bigger caps.


Just went to the local thrift and grabbed all the 1.5 amp 12v linear psu' s I could find.
I'll recap them and use them instead of the switching setup I have right now.

[SamIAm]

I recently started using a 9V 2.5A SMPS with all of my AC-adapter-reliant consoles. While I haven't measured the ripple on it, it does seem to get along with everything just fine (AV Famicom, SFC, Duo-RX, SGX/SCD combo, X'Eye, 32X). I suspect that SMPSs with higher amp ratings are likely to have quieter ripple, so that's the first thing I'd look for. That and, you know, a quality manufacturer.

There is also a great degree of variation among consoles in terms of how much decoupling capacitance they have before the 7805 regulator. A Duo-RX, for example, has two nice fat 1000uf caps, one before each of its two 7805s (one powers CD stuff, the other powers main processors and RAM), and also two 330uf caps after them. Meanwhile, the basic PCE and SGX systems only have one 47uf cap on each side of the 7805. Per the datasheet, 7805s are also supposed to have a ceramic decoupling capacitor as close as possible to the base of the input, but the SFC neglects this IIRC.

[ASDR]

I'd say the rectifier is there to rectify, not make things safer. I don't think adding more filtering capacitors to a linear PSU makes a difference. SMPS leak AC and often have a whole capacitor network to help remove the noise at various frequencies, but I don't think you get anything other than the low frequency ripple from a linear PSU. And that should be taken care of by the linear regulator inside the console. When I tried to find answers why the LM7805 regulators need the two capacitors and how they arrived at the recommended values in the datasheets I found some widely varying answers, seems like at least for some models in some situations they're safe to omit. I don't think you need any 100nF decoupling capacitor in the PSU and I think the caps on the console side are likely for bypassing. EEVBlog recently had two videos on the subject:

https://www.youtube.com/watch?v=P8MpZGjwgR0 (Are Bypass Capacitors REALLY needed?)
https://www.youtube.com/watch?v=1xicZF9glH0 (Bypass Capacitors Visualised!)

Haven't watched the second one yet, but the first one was neat.

[maxtherabbit]

I'd say the rectifier is there to rectify, not make things safer. I don't think adding more filtering capacitors to a linear PSU makes a difference. SMPS leak AC and often have a whole capacitor network to help remove the noise at various frequencies, but I don't think you get anything other than the low frequency ripple from a linear PSU. And that should be taken care of by the linear regulator inside the console. When I tried to find answers why the LM7805 regulators need the two capacitors and how they arrived at the recommended values in the datasheets I found some widely varying answers, seems like at least for some models in some situations they're safe to omit. I don't think you need any 100nF decoupling capacitor in the PSU and I think the caps on the console side are likely for bypassing. EEVBlog recently had two videos on the subject:

https://www.youtube.com/watch?v=P8MpZGjwgR0 (Are Bypass Capacitors REALLY needed?)
https://www.youtube.com/watch?v=1xicZF9glH0 (Bypass Capacitors Visualised!)

Haven't watched the second one yet, but the first one was neat.

learned a new phrase from the first video - "half a bee's dick"


edit: just finished the second video, it was fantastic. really the best "practical" explanation of bypass caps I've ever seen

[syboxez]

The diodes in the stock PSUs are what convert AC to DC, and are very important. You can learn more about exactly how this type of PSU works here: https://www.youtube.com/watch?v=cyhzpFqXwdA

Note that when he talks about forward voltage drops, he is talking in theoretical terms, and as he briefly mentions, temperature, current, and type of diode can vastly change this number. So basically, when you're designing something that uses diodes, you want to handle the forward voltage as a range between 0v and whatever the datasheet says. For unregulated linear power supplies, this is all but irrelevant.

As for further cleaning power, which shouldn't be necessary as the 7805 inside the console would take care of all of that as the linear PSU is only outputting a 120Hz (or 100Hz for PAL regions) ripple. So long as the minimum voltage in that ripple is greater than or equal to the minimum input voltage of the 7805, there should be no issue. If you would like to further smooth out the power anyway, you could build a Pi filter: https://en.wikipedia.org/wiki/Electroni ... 80_filters. A 3300uF capacitor should be good enough for the load that these consoles are putting on the PSU though, so I still do not think it's necessary.

Where a Pi filter could come in handy is fixing the white line issue on SNESs by putting a Pi filter on the output of the 7805. I did that, and the white line completely disappeared. You can clean up other similar low frequency noise in the same way. For high frequency noise, you need a different approach. Putting a decoupling capacitor with as low of an ESR as possible (generally SMD ceramic capacitors) as close to the problem-causing IC as possible will reduce the problem. This for example applies to some forms of jailbars, like what is seen on the SNES or PC Engine, but not the Sega Genesis/Mega Drive or the checkerboard pattern on some SNES revisions, whose jailbars are caused by a bad PCB layout.

[thebigcheese]

HD Retrovision has a recommended power supply on this page: https://www.hdretrovision.com/vote3rdparty/. I use it on all my consoles (except the Genesis/Sega CD combo) and I've not had any issues. No added noise or interference.

[syboxez]

HD Retrovision has a recommended power supply on this page: https://www.hdretrovision.com/vote3rdparty/. I use it on all my consoles (except the Genesis/Sega CD combo) and I've not had any issues. No added noise or interference.

It is extremely difficult to get the design of switch mode PSUs right. This is one of them that did get it right.