SNES PSU

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Lopenator
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Re: SNES PSU

Post by Lopenator »

I didn't miss the point I know exactly what you did. I was only asking if all you did was swap the wires around in order to reverse polarity. I was just misunderstood, sorry.
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NewSchoolBoxer
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Re: SNES PSU

Post by NewSchoolBoxer »

VajSkids Consoles wrote:https://www.youtube.com/watch?v=RbHH9n4lSio

Also check this out, It should be called "How not to make a Sega Saturn PSU board - hackery ahead!
Moving the AC to DC conversion outside the console is good idea but no filtering capacitors is extreme bad idea, as is lack of thermal calcs for determining if that heat sink is enough. What we get when people learn electronics through YouTube. Not that I didn't learn some things that way..

No one on Amazon told me they had linear PSUs but I did get a list of 4 linear regulated PSUs that Sweetwater Audio sells. Issue is most current they output is 300mA. In theory could tie 2 outputs together in parallel for 9V with 600mA but you're at $15x2 + adapter chain that you have to DIY. That such an adapter doesn't exist, should say is not recommended.
-------------------
OPTION A
If you want to stay with linear unregulated, and I'm saying you should NOT, Jameco sells the perfect 9V 1A, 5.5x2.1mm negative center PSU for PAL and SFC for $9. Just need Console5 adapter for NA. Advantage of using over OEM supply is that it doesn't have aged electrolytic capacitors and no kid dropped or stepped on it a few times or stored it in humid attic for last decade.

OPTION B
Note that PAL SNES and all NES can take positive or negative polarity DC or 9V AC. I checked and the Jameco mains AC to 9V AC converter that Lopenator linked is regulated, so perfectly fine for those.

OPTION C
Jameco has a linear regulated, 9V 0.5A, 5.5x2.1mm negative center PSU for $11 that you could use. VajSkids Consoles did it and I used a 250mA one for a minute. I realize 2 people is circular logic / works until PSU burns. Thing is, PSUs that aren't crap have max current and heat detectors for auto shutoff and can run slightly above the rated current at reduced life expectancy. At $11, I'm okay with that. Gven that my measured power readings include losses in the PSU, Star Fox and Super Game Boy shouldn't have drawn above 450mA.

I get my $40 SFC 2CHIP from Japan on Monday that hopefully will boot with the SD2SNES flash cart and then I can try Japanese carts of Mega Man X2 and Yoshi's Island with their enhancement chips. Need to see this before recommending Option C. Is "okay" as of now.

OPTION D Proposal
New idea I thought of is 9V battery strat. 9V is a lie, is really 8.4V that ticks down and lasts about 1 hour before dropping below 7V that no 7805 will accept. Trick is to use a 9V battery rechargeable via USB and charge while playing. Lithium-Ion can charge at 5Vx1A and with SNES pulling 5Vx450mA or less, this might work. Batteries output clean DC and it's in the manufacturer's interest to reduce ripple voltage/current since that power is useless and just drains the battery faster. No need for line regulation, lack of load regulation a little concerning but Game Boy and friends get away with it.

So I got 9V battery + Mr. Power guitar pedal 9V to 5.5x2.1mm center negative adapter also coming on Monday. This plan has the potential to be the best unless I'm dumb and it can't actually work and charge at same time.

OPTION E
I guess I got to call retro game shop and ask about the 680mA linear PSU that has barrel for NA SNES + 5.5x2.1mm for PAL and Japan. VajSkids Consoles, if you got a plug for linear 9V 1A PSUs for Master System, let us know. Just as compatible with SNES as the other 5.5x2.1mm PSUs.
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Lopenator
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Re: SNES PSU

Post by Lopenator »

It seems like linear PSU are getting harder and harder to come by. Switching PSU are everywhere.

I have seen your option E on eBay. I was going to buy one but I'm not how sure how confident I feel in the build quality of them. Perhaps the one you have is good but I could get a dud on eBay. I did have it in my cart though.

I also checked retro game shop online and couldn't find the psu you got from them. Maybe they are not in stock anymore.

I'm interested in the battery idea you came up with. Seems like it might be the most effective route. I can picture myself now sitting in my living room and a few friends come over and I plug my SNES into a battery. lol. If it works it's something I'd be interested in.

I did order this one. It seems to be similar to yours from retro game shop but 10v and 1000ma. I just hope it's regulated and built like crap.

https://www.ebay.com/itm/265606716718?m ... media=COPY
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Re: SNES PSU

Post by VajSkids Consoles »

I'm not sure what you mean by a plug?
that one I hacked up is my new supply :P
it came from an Australian site specialising in power packs. That's •all• they sell. Everything on the site has proper certification to be used on the outlets here.
The 230v outlets that Ive called 240v my entire life :P
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Re: SNES PSU

Post by VajSkids Consoles »

Though I wont be playing my 1-chip fats or juniors anytime soon as I had an N64 to mod and had to remove the resistor in the SCART head for attenuating sync.

it was a dumb idea to ever add it there given I had the option to use the SMD one and pass it through to the composite line in the console.

Also, 1-chip 03's are definitely no sharper than prior revisions!
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Re: SNES PSU

Post by VajSkids Consoles »

Lopenator wrote:I didn't miss the point I know exactly what you did. I was only asking if all you did was swap the wires around in order to reverse polarity. I was just misunderstood, sorry.
Yes, thats all a centre negative supply is. I ran the negative to the centre pin and the positive to the outer ring. This is a totally fine power pack. I've used cheap switching supplies with the little voltage selector and they're noisy as all f__k (video interference), but these are ones are ok.
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Re: SNES PSU

Post by NewSchoolBoxer »

VajSkids Consoles wrote:I'm not sure what you mean by a plug?
that one I hacked up is my new supply :P
it came from an Australian site specialising in power packs. That's •all• they sell. Everything on the site has proper certification to be used on the outlets here.
The 230v outlets that Ive called 240v my entire life :P
People living in Australia aren't going to buy 110V/60 Hz PSUs for US/CAN outlets. Can you share the Australian site?
Lopenator wrote:It seems like linear PSU are getting harder and harder to come by. Switching PSU are everywhere.

I have seen your option E on eBay. I was going to buy one but I'm not how sure how confident I feel in the build quality of them. Perhaps the one you have is good but I could get a dud on eBay. I did have it in my cart though.

I also checked retro game shop online and couldn't find the psu you got from them. Maybe they are not in stock anymore.

I'm interested in the battery idea you came up with. Seems like it might be the most effective route. I can picture myself now sitting in my living room and a few friends come over and I plug my SNES into a battery. lol. If it works it's something I'd be interested in.

I did order this one. It seems to be similar to yours from retro game shop but 10v and 1000ma. I just hope it's regulated and built like crap.

https://www.ebay.com/itm/265606716718?m ... media=COPY

Oh sweet you found the adapter with same branding in 1000ma form. In "similar sponsored items" I found mine at 680ma. That it doesn't need $4.50 Console5 adapter, fits all SNES, most NES and some Sega consoles, $5+$4 shipping is insane! Is definitely too heavy to be switching and I'd be surprised if unregulated. Way I think to prove is measure voltage before 7805 input at low power and high power draws. Unregulated, the PSU output voltage will shift between 9 and 12V.

Build quality at that price, you're right to be suspicious. Otherwise I'd say everyone buy this now! And like, switching PSU is great option IF someone figures what capacitors to solder on input and output of 7805 to filter the low MHz noise. 10uF tantalum? Being real, people want a no solder solution. Modern switching PSU is "okay" option otherwise.

Linear PSUs dying out, I'm not sure why at 10W and below. In theory they're cheaper to make but switching frequency in the MHz range, maybe that does reduce the transformer and RLC sizes enough to win out. Else better for manufacturing to be all switching, outside of lab bench niche where people will pay for ultra low noise to make ideal reference voltages.
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Re: SNES PSU

Post by VajSkids Consoles »

what's your opinion on.

MS-305D Variable Linear Adjustable Lab DC Bench Power Supply 0-30V 0-5A 150W

it's quite well priced, but I doubt eBay and AliExpress stuff ever pass any stringent quality checks
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Re: SNES PSU

Post by NewSchoolBoxer »

VajSkids Consoles wrote:what's your opinion on.

MS-305D Variable Linear Adjustable Lab DC Bench Power Supply 0-30V 0-5A 150W

it's quite well priced, but I doubt eBay and AliExpress stuff ever pass any stringent quality checks
Thanks for site link!

I'm really impressed with the specs on that and the fan that only turns on if needed since the vibrations would add electrical noise.
Ripple and noise: CV ≤ 10mV (RMS) CC ≤ 20mA (RMS)
10mV max noise + ripple in constant voltage mode is what I want to see. Was 50mV on a $200 lab bench PSU I was looking at. Granted, MS-305D specs don't clarify if measuring at standard 20 Hz-20 MHz bandwidth and AliEpxress isn't going to do anything about numbers being fudged. Still for $100, is best I found in half an hour of browsing. I see listed on US Amazon and Newegg too.

What's pretty cool is a DIY linear regulated PSU kit for $32. One output is adjustable from +5 to +15V and the other to -5 to -15V. The 175mA to 750mA current per supply is good enough. Minimum current there is to prevent a voltage spike, whereas lowest reading I found in SNES so far is ~250mA.

Nice circuit diagram in the instructions. Half the cost is in the transformer, which is basically saying there is no money to be made in making a PSU outside China. Another $9 for metal enclosure. Might be worth swapping in brand name capacitors if not also a series inductor and test for reduced ripple.
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Lopenator
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Re: SNES PSU

Post by Lopenator »

A diy PSU kit would be awesome to do. I'm highly considering getting that.
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Re: SNES PSU

Post by NewSchoolBoxer »

I want to buy the PSU kit too. The $13 UPS shipping holds me back if I don't have other things to buy but I see US Amazon has for $37 + free shipping. I want to test upping the main cap from 2200uF to 3300uF or the max voltage rating for lower leakage current. The aluminum case shields high frequency noise that the 7805 won't filter, versus a plastic case that blocks nothing. Wrapping a plastic PSU case in aluminum foil isn't a crazy idea.

There is the thought of overkill on minimizing ripple. I see stated figures for new linear PSUs of 1-10mV. Where do people care about PSU ripple? For their expensive computers! Tom's Hardware has a summary:
The ripple limits, according to the ATX specification, are 120mV for the +12V and -12V rails, and 50mV for the remaining rails (5V, 3.3V, and 5VSB). Nonetheless, in modern PSUs, we expect to find a much lower ripple.
Tier 1 Corsair at 5V rail has 7mV ripple and worst Gigabyte has 30mV. I'm sure all are switching. Barring SNES audio, I don't think there is any realizable benefit for PSU ripple below 10mV and can go with safe upper limit of 50mV that feeds into 7805's 60 dB of low frequency filtering = a 1000x drop. Linear PSU noise of 50mV becomes 50uV on the output and the 1uF capacitor will further reduce.

Computer PSUs are better. Our low power switching PSUs push out 100-150mV ripple and the main problem is overheating capacitors in the console, including any in ICs. Elevated temperatures reduce lifespan. On one hand, I imagine 5W, SD video SNES tolerating higher ripple than 500W, HD video computer built to run 24/7. On the other hand, SNES is an antique originally sold at a loss with bundled unregulated PSU to save $1. Have to use temperature probe and see the difference between clean and dirty power...without shorting pins together.

Secondary problem is MHz switching noise interfering with video and clock timings but can just look at video output and compare.

Audio different story. Takes the DC input voltage before it hits the 7805. Output should be line level 316mVrms or less. SNES audio is far below 96 dB music CD spec but it's plausible reducing the PSU ripple into the uV range could boost the sound quality, if you had high quality speakers.
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Re: SNES PSU

Post by NewSchoolBoxer »

Super Famicom came in just 3 days from Japan. Thank you DHS for beating the estimate. I opened to verify it's a 2CHIP from 1990. SD2SNES flash cart fits in slot but doesn't work. Does no one test their crap on Japanese consoles?! Learning if flash carts are safe for power consumption is a big deal.
Spoiler
Image
Three discoveries:
------------------------------------------------------------

1. I believe we can verify if 1CHIP without opening it up
Seems 2CHIP consumes significantly more power. This makes sense given the two video processor chips in 2CHIP are combined with the CPU into, you know, one chip. Verifying without opening console preserves the warranty from retro game shops. Just want someone else with a 1CHIP to confirm. I can fix or buy more 2CHIPs.
Spoiler
Image
Use a linear PSU like the one your console came with and see at least 8W? It a 2CHIP. Serial number itself not proof when PCBs can be swapped.
------------------------------------------------------------

2. The retro console PSU Lopenator and I bought is unregulated
Sucks being wrong. Lopenator, guess you can return under that basis. Such an easy test, should have realized before. Probing multimeter on PSU is same thing as low load. If no regulator then voltage output is well above 9V.

Sure enough, all 4 linear PSUs I have did over 12V that would be impossible with a 9V regulator added on. Switching was ~9V as expected. That it is "switching" refers to its method of voltage regulation.
Other confirmation is Gator Cases polarity adapter converts (-) to (+) as well as (+) to (-). I would think all polarity converters go both ways.
Spoiler
Image
Image
Image
I still like our retro console adapter for powering all SNES/SFC with no barrel chaining. Remains a step up from OEM. Turns out the Japanese OEM only lasts 2-3 minutes before console shuts off. All the 90s PSUs will fail in due time without a recap.
------------------------------------------------------------

3. LDO found with same pinout as 7805 that filters switching PSU noise
I brute forced and found several LDO 5V, 1-1.5A regulators that have the same pinout as 7805. One had the graph in the datasheet I was looking for. Switching PSU moves up to the same level as linear regulated. If you buy a PSU with adjustable output, can feed 6V for 83% efficiency, up from 9V 55%. Trick with LDOs is follow the datasheet notes about capacitors and stability. You cause the output to oscillate, could be gg for console. Keep heatsink since the steel cage blocks EMI.

LM2940T-5.0/LF08 for $1.99
Output bypass capacitor must be at least 22 μF to maintain stability.
Spoiler
Image
-70 dB is a ripple/noise reduction of over 3000. 150mV ripple becomes 48uV.
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Re: SNES PSU

Post by VajSkids Consoles »

LM2940 is my favourite LDO
I have a few of them left from bulk buy
my model 1 megadrive rocks a pair (cheap switching supply with these still = video interference)

though mine are LM2940CT

You likely have a dirty cartridge slot.
I have being dealing with bulk amounts of 2-chip (or 3chip) consoles for a while.

They almost always work..
Run them through the old burn in ROM
The ones that haven't worked have being simple things like buzz on audio (the amount of these I have, it's not worth my time to investigate) or dead 7805.

90% of them need multiple re-insertions of cartridge to load.

I had one that flat out refused to load one particular title but passed all tests.. I can't explain that.
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Re: SNES PSU

Post by VajSkids Consoles »

if you have a sacrificial cartridge and you're being lazy, flood the pins with isopropryl and smash the sacrificial cart in and out, use a cotton tip as you go to clean the cart edge connector , essentially using sacrificial cart as a cleaning tool.

best to just clean it properly though.
I think you'll find it works fine
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Re: SNES PSU

Post by Lopenator »

Newschoolboxer. I can test 1chip if you need. Just let me know exactly what to look for.

Do you think the LDO you found is better than 7805 L78S05CV? I currently have that one installed. Which capacitor is the output bypass capacitor?
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Re: SNES PSU

Post by NewSchoolBoxer »

I'm sure you're right about dirty cart slots when 1/4 boot on first attempt, 1/4 boot on 2nd-3rd attempt and 1/2 don't boot at all. I have 99% isopropyl alcohol. Trying to avoid manual labor but the time has come. I like how there is a seller doing buy 2 SFC, get 1 free. Maybe I need to stock up while still cheap and plentiful. Then one dying doesn't stop my progress.
Lopenator wrote:Newschoolboxer. I can test 1chip if you need. Just let me know exactly what to look for.

Do you think the LDO you found is better than 7805 L78S05CV? I currently have that one installed. Which capacitor is the output bypass capacitor?
Sweet, idea is test the power in watts with a meter from 2 or 3 relatively common or popular games. Real carts and inefficient linear PSU. Hopefully one that has an enhancement chip like Star Fox, Super Mario Kart, Kirby Super Star or Super Mario RPG. I have all those. Not a title or loading screen since those are low power. Check from first level or stage of your choice of sitting idle or pressing buttons since game is polling the controller either way. If you have a flash cart then one of the same games played from that. If you're getting 4.5-7.5W on a 1chip then that's all the evidence I need!

LDO being better than L78S05CV, it depends. I bought the L78S05CV myself. If you're using a switching PSU then LDO is definitely better. Linear 9V source is the same. The LDO also lets you dial down the PSU voltage to, say, a safe 6.25V to significantly reduce the console heat. Is debatable how much that helps since SNES has a large steel heat sink for the 7805 taking 9-10V. Then you have to buy an adjustable voltage PSU.

If someone can show a temperature drop of 10°C on chips or capacitors with the lower PSU voltage then that would be a compelling mod. Maybe VajSkids Consoles can tell us if 22μF tantalum is good or go 33μF for expected decline in rated value over years. Edit: do not add in parallel to C81, remove C81 due to its low ESR.
Image

Here's the section describing the bypass capacitor:
Spoiler
Image
It's saying that capacitors in parallel, despite capacitance adding, the ESR works like two resistors in parallel. Thus ESReq = (ESRc1 * ESRc2) / (ESRc1 + ESRc2)
For 1 console, I'd rather just buy 1 tantalum.
Last edited by NewSchoolBoxer on Tue Jul 19, 2022 1:03 am, edited 1 time in total.
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Re: SNES PSU

Post by NewSchoolBoxer »

Well if C81 is ceramic and not electrolytic then it has to be removed because its low ESR will overwhelm the tantalum's for the LDO. I'd have to remove the heat sink to check but circuit diagram suggests its non-polar and therefore low ESR. Then either replace with 22μF min tantalum or go 6μF min tantalum and 16μF min aluminum electrolytic in parallel like section says.

I guess LDO downside is it takes actual thinking versus drag and drop 7805. Someone going to do this and leave the ceramic in and oscillate the output.
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Lopenator
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Re: SNES PSU

Post by Lopenator »

I'm about to buy sfc also lol
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Re: SNES PSU

Post by NewSchoolBoxer »

Yeah! Half price Japanese consoles is where it's at. Japanese PSP and Neo Geo Pocket/Color have an English language menu option.

I wanted to lay out the rest of possibilities before rechargeable 9V batteries come. Unless I'm dumb and they can't output and charge at the same time, I predict it's the best option for overall cost + low noise + ease of use + utility on other electronics projects. Plus it feels degenerate.

The major downside is no load regulation on console power demand climbing up or down, but is less a downside than using linear unregulated since a charged battery's output is fixed. Then you need a $6 9V barrel adapter + maybe $4.50 w/ $5 shipping NA SNES adapter.

Just read what you want. Not intended to be a reference guide. Most of what I'm proposing is theoretical versus proven. I put what I thought was most helpful first.

--------------------------------------------
Ferrite Bead on Switching PSU
Spoiler
I believe a low MHz ferrite bead is a smart solution to slide onto a switching PSU. Not going to suppress to the level of 70 dB LDO but a <$1 bead like this looks good for a no mod / no solder solution. In fact, I'm going to buy a bead or two. We want the highest impedance possible at 1 MHz you see on datasheets. The clamp on ones are nicer but cost $4-5.
Not useful for linear PSUs that have no MHz noise.

Sony's JP-21 RGB cables for PS1 contain 2 ferrite beads and the beads are the cylinders you see on most computer power cables. A bead does result in a small power loss so can't stack them on to oblivion. I'll measure with meter the additional power output, if any, else the voltage drop should be far above regulator cutoff. Does force me to use oscilloscope to measure the noise reduction.
5V USB to 9V Barrel Converter
Spoiler
It so happens that a switching IC can be used to form a charge pump to double or triple the input voltage. I found a USB to 9V 5.5x2.1mm negative center barrel adapter for $9.

Max current of 800mA shouldn't be an issue outside of +5V rail abuse like the 100mA Bluetooth controllers OR 1100mW (220mA) from LM1881 sync stripper for PAL consoles. Luma as sync is good enough for most purposes. Renesas ISL59885 strips for 400mW (80mA) with same pins if just need CSYNC out.

The real issue is noise. USB 5V power has a noisy reputation already that will come in the high MHz range. Can ferrite bead that down. Charge pumps also have a noisy reputation that come with kHz switching noise, which is too low for any ferrite bead. Upside is that the 5V being regulated essentially means the 9V is regulated too. If the noise is low enough in the kHz range to fall into the 7805 filtering, could be good option for the price.

Most people don't have an oscilloscope to measure USB port noise but we're not the first group to want to know the cleanest 5V source. I'm sure the information is out there. PhD in EE Mike from Retrotink recommended a television's USB port to power one of his products.
Expensive 9V Linear Regulated PSU
Spoiler
The only 9V Linear Regulated PSU I've yet found is $32.29 from China and comes as (+) polarity. I do like their explanation and pics on why linear is better than switching. Nichicon (if not counterfeit) is tier 1 cap brand. I assume is real due to sky high price for Made in China. Stated 10mV ripple is believable. I like this option if you can tolerate the price for gain of having a no mod / no solder solution, even though you're out even more for adapters.
12V Regulated Linear PSU
Spoiler
Actually, 12V linear PSUs in regulated and unregulated form are readily available. Unregulated are particularly cheap, with the center negative 12V/1.5A PSU going for $10.95 and a 12/1A positive one on clearance for $4.56!

Console5, whose engineering efforts I almost always respect, mentions at the end of their NA SNES adapter page that 9-12VDC supplies are fine to use. Versus 9V supply, we're talking dropping 7805 efficiency from 55% to 41% and thus adding significantly more heat. I can take the risk and measure the capacitor and IC temperature difference on a $40 console. A 2-3°C increase would be acceptable.
DIY 12V Unregulated to Regulated Conversion
Spoiler
I'd say you want regulated except there is the possibility of adding an external 9V regulator + 2 capacitors on the 12V output. Is how the DIY kit I like works. Think I'd take a kit like this and swap in a different regulator for 9V and use similar 2x 1uF/35V+ tantalum capacitors the DIY kit includes.

Why 35V capacitors when 16V or 25V is cheaper? The higher max rating you go, the lower the leakage current and therefore slightly better efficiency. 1 pigtail to barrel adapter or equivalent on the output is needed that you can connect red to (-) and black to (+) on the PCB to get negative polarity in the barrel. While a convoluted design, I don't think we're running out of cheap linear 12V PSUs in the near future. An assembled kit could be sold for another no mod / no solder path.
Bad Idea: Switching Regulator Swap for 7805
Spoiler
I'm not going to link the Reddit thread and help its SEO. The person installed switching PSU on several consoles like the one I mentioned that is pin-compatible with 7805 and bragged about it running cooler. As u/famine- points out, this is a downgrade because the switching regulator injects 20-50mV ripple directly into Vcc with just 1 capacitor left to filter it. Imagine the noise stacking with a switching PSU.

Of note is LukeEvansSimon who posts here too said in-discussion that the 10V linear PSU that came with NA consoles does sky high 500mV ripple. The 7805 alone cuts that low frequency noise to < 1 mV, making that tolerable to video but ages filtering capacitors and audio. I assume not recapped since I don't perceive how 500mVrms ripple is mathematically possible from a linear PSU.
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Lopenator
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Re: SNES PSU

Post by Lopenator »

The expensive aliexpress PSU is super tempting for me to buy. Does straight 5521 mean the barrel is 5.5mm x 2.1mm? It says the polarity defaults to both positive and negative.
Last edited by Lopenator on Tue Jul 19, 2022 6:48 pm, edited 1 time in total.
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Re: SNES PSU

Post by Sirotaca »

I recently bought an oscilloscope (Siglent SDS1104X-E) to play around with, so I thought I'd try taking some actual measurements to add to the discussion. I tested an original 30-year-old Nintendo linear power supply against a Triad WSU090-1300-R with an RGB-modded SNS-101 running SMW's attract screen on loop (giving it a few minutes to warm up between each test). I haven't used oscilloscopes much, so forgive me if I've made any mistakes.

First up is the Triad, measured at the input side of the 7805:
Image
Around 85 mVp-p, not too bad.

Next, let's try the Nintendo power supply:
Image
Um, lol. We're sitting at 500 (!) mVp-p here. Either time has not been kind to this power supply, or they were some hot garbage right from the factory. Either way, the Triad is clearly a massive improvement despite being a switching power supply.

Measured on the output side of the 7805, both were about the same at ~36 mVp-p.

Triad:
Image
Nintendo:
Image

For me, the really wild thing about these measurements is that I've seen plenty of people complain of visible image distortion caused by low-quality generic power supplies. Makes me wonder, just how bad do those generic power supplies have to be if my original power supply with its 500 mVp-p of ripple isn't enough to do it?
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Re: SNES PSU

Post by Lopenator »

That's insane! It's your PSU in good condition? Has it had capacitor replaced?
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Re: SNES PSU

Post by Sirotaca »

It's untouched, but I've been using it with no problems. Having seen these results, I may try recapping it and taking before and after measurements.
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Re: SNES PSU

Post by NewSchoolBoxer »

Lopenator wrote:The expensive aliexpress PSU is super tempting for me to buy. Does straight 5521 mean the barrel is 5.5mm x 2.1mm? It says the polarity defaults to both positive and negative.
Image

It's the only professional linear regulated supply I've seen in existence. My "interpretation" is that 5.5x2.1mm is the barrel size they ship unless you ask for 5.5x2.5mm instead. Is positive on the center and negative on the outside = positive polarity.
Sirotaca wrote:For me, the really wild thing about these measurements is that I've seen plenty of people complain of visible image distortion caused by low-quality generic power supplies. Makes me wonder, just how bad do those generic power supplies have to be if my original power supply with its 500 mVp-p of ripple isn't enough to do it?
Thanks Sirotaca!! Great work! I criticized Triad for listing a high 150mVrms ripple in the datasheet whereas most everyone else was around 100mV. As the listed maximum possible value, maybe they were being conservative and ripple is good (for switching) in reality. Datasheets use 20 Hz to 20 MHz for ripple measurement but the full bandwidth like you did is what matters. Ripple at 50 MHz still going to heat and age things, although probably not PSU's fault.

Can you do FFT mode with the Triad on 7805 pre and post 7805 to see what frequencies the noise sits at? Nintendo's ripple at 120 Hz is expected. Its dB reduction is 20*log10(39.4/496) = -22.0 dB and Triad's is 20*log10(35.2/85.6) = -7.72 dB. That every 7805 datasheet shows -60 dB or better on low frequency noise and SNES has a 1000uF capacitor for low frequency filtering under the heatsink, I'd expect much better on Nintendo.

Very helpful you showed some MHz filtering capability exists stock from capacitor network, however insufficient. 500mV from Nintendo is insane! In my last reply, I mentioned someone else measured 500mV. But I think the high ripple from Nintendo and after the 7805 is explainable. Nothing works as well as it used to 25 years ago. People removing white streak with lolzy huge new capacitor could be achieved just with new 7805 or LDO + new C81.

Electrolytic capacitors dry out and lose capacitance. I was looking at 220uF to buy for cables and the rated value is only guaranteed ±20% for the first 1000-8000 hours of use, with higher hour capacitors costing more. A moderate 20 hours a week for a kid with free time is 1000 hours/year.

edited to give oscilloscope measured ripple versus Vrms ripple
Maximum Ripple Calc Prediction for Nintendo Linear PSU
Spoiler
Not a LTI system so only an approximation. Vdc is 10V in Nintendo PSU and sqrt(3) factor is due to switching noise being modeled by a triangle wave. The f is 60 Hz for NTSC, typical R is 560-4700 ohms. Low value is smaller voltage drop but worse ripple. Let's go with 560 to be conservative. C, well, C depends on your design goal since high capacitance is more expensive. Let's roll with 1000uF since the console uses one for same purpose.

Before RC filter:
Vdc here is the secondary Vdc off the transformer that is less than the Vdc voltage the load sees. Vdc the load sees is by definition 10V = Vpeak aka Vm.
Vpeak = 10 = Vdc (secondary) + Vripple (peak to peak) / 2
Ripple Factor = 0.483 for full wave rectifier = Vripple (rms) / Vdc (secondary)
Vripple (rms) = Vripple (peak to peak) / Vripple (rms)
-> Vripple (rms) = 0.483Vdc (secondary) = Vripple (peak to peak) / (2 * sqrt(3))
-> Vripple (peak to peak) = 1.67316*Vdc (secondary)
-> 10 = Vdc (secondary) + 1.67316*Vdc (secondary) / 2
Vdc (secondary) = 5.45V
Vripple (rms) = 0.483 * 5.45V = 2.632V
Vripple (peak to peak) = Vripple (rms) * (2 * sqrt(3)) = 9.117V

After RC filter:
Vripple (peak to peak) = Vm / (2 * f * R * C) = 10 / (67.2) = 149mV
Vripple (rms) = Vm / (4 * sqrt(3) * f * R * C) = 10 / (233) = 42.9mV
Alternatively, Vripple (rms) = Vripple (peak to peak) / (2 * sqrt(3)) = ~42.9mV
149mV (peak to peak) is expected ripple voltage seen on oscilloscope = 42.9mV (rms)

Observed ripple 500mV being much worse than the worst possible prediction and worse than switching PSU is a big red flag. I'm sure recapping PSU will help! Typical C is 2200uF or 3300uF. 2200uF and better R of 4000 ohm would drop expected ripple to 9.47mV. If you do open PSU, let us know the R and C values.
Sirotaca
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Re: SNES PSU

Post by Sirotaca »

Hopefully I'm doing this right.
https://imgur.com/a/uVfMhuM
Not much to talk about below 10 kHz. There are peaks at 15.7 kHz (horizontal sync frequency), 32 kHz (audio sample rate), and their harmonics, plus a small peak at 22.6 kHz that disappears after the 7805. Otherwise the input and output sides of the 7805 look more or less the same.

Unfortunately, Nintendo used some dumb security screws that I don't have a bit for, so recapping the original power supply will have to wait. I'll pick up a driver next time I do an order from Console5.
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NewSchoolBoxer
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Re: SNES PSU

Post by NewSchoolBoxer »

Thanks Sirotaca! This is badass. So the Triad does a good job filtering its own high kHz or low MHz switching noise in that I can't tell what the fundamental frequency is. The standardized dbV scale means a reference voltage of 1V. Useful to make the denominator 1 for noise calcs. For our scale of 5V regulator output and 9V output, 10mV of dbV (-40 dB) noise equates to 50mV and 90mV, respectively. Interestingly (to me), consumer audio level of 316mV (rms) is exactly -10dbV below 1V.

I would say 1mV noise at 5V reference, post-7805 is very safe to ignore. We care about 10mV noise or greater. This equates to -54 dbV or less, i.e. closer to 0 dB, for the level we care about and -74 dBV or greater, i.e. -74 to -100 dBV, being safe to ignore. The -54 to -73 dBV in between range, that matters kind of like a sliding scale. Is noise at a critical a critical clock, video or audio frequency or harmonic that will interfere, or are we really just measuring their own noise they generate?

This is to say, improving the filtering at frequencies where we see the biggest area under the noise curves will bring the greatest improvement, barring significant noise at a frequency the SNES uses.

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General Conclusions

SNS-101 measured here is an RGB modded SNES Jr. (1CHIP) model. Can't necessarily draw same conclusions to stock console or other revisions.
Spoiler
Image
Image
Image
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1. Noise above 128 kHz in the graphs is too low to matter and that's a positive for the PSU. My judgement is Triad is 'okay' to use in terms of not aging electronics and 'very good' on not causing electromagnetic interference outside the 100/120 Hz to 1 kHz (with harmonics) range that all PSUs contribute noise to.

We know not all PSUs are equal but it's possible a modern LDO will crush noise enough across all frequencies to make any non-trash PSUs 'good' for our sake. Risk of blowing the console from LDO instability so test on a $40 SFC? A new 7805 would be a good test to see if low kHz can get pushed under -74 or so dBV to make the Triad switching power supply super safe.

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2. Switching PSU has no circuitry that would generate exactly 15.7kHz NTSC horizontal sync or or 32kHz audio sampling rate or 3.52-3.70 MHz colorburst for Composite and S-Video. These noise sources are caused by the console itself on the power supply as soon as it enters the console! Colorburst noise too low to matter but the sync especially and audio to a lesser extent are significant.

In other words, console architecture dirties up its own power supply but modding may make worse.

The multiout and U7 video encoder are too close for comfort though true of normal sized consoles as well. SNES Jr smaller size is itself concerning given smaller distance between key parts and less enclosed volume for heat dissipation. EMI strength declines by square of the distance, meaning, 2x as far away has 4x less signal strength. Meaning EMI from APU, CPU/VPUs/1CHIP should be less on the power line with normal sized consoles.

When you're done RGB bypassing, is it normal to leave the steel shielding/heatsink off like this or put it back on? The wiring addition, which is not coax and has effectively zero shielding both to block EMI and prevents its own EMI from spreading, is concerning, more so if any steel shielding that protects against low frequency EMI is removed.

I'd like to see a mod using real 26 AWG or thicker coax cable since coax has a second outer conductor to block EMI. Different routing path of new wiring should also be considered. Raising it in elevation would increase the distance and therefore reduce the EMI. Not sure if reduced flexibility makes modding any harder.

--------------------------------------------------

3. Biggest noise source on power line feeding into Vcc is 120 Hz AC-to-DC noise from PSU by far and second biggest is horizontal sync frequency of 15.7 kHz from video. The noise floor looks to be a surprisingly good -100 dbV. Would be physically impossible to reduce noise below this level, not that we need to.

Sirotaca's measured PSU ~85mV (peak to peak) from first reply = 25mV (rms) noise at 120 Hz, is -32 dbV = -18 dB with 5V scale. I very much like seeing the FFT match that at the -30 dbV peak that is visible on second pic. Room to improve the < 1 kHz filtering. Video and audio improvement will be much more difficult. Even if we solve it here, the EMI infects the whole console.

Due to power growing on a log scale, filtering 15+ kHz noise better on the incoming power line may not matter much except for keeping video sync noise away from audio. Best solution would prevent EMI from leaking out from the chips in the first place. Something like an additional EMI shield. Lowering the temperature would reduce noise only to a very limited extent. A 5-10°C reduction is more about chip and capacitor aging.

--------------------------------------------------

Harmonics Explanation
Spoiler
The SIGLENT chart on side giving noise at peak frequencies is amazing. You see the 15.7 kHz noise in 3rd and 4th pics right? Square wave of sync and RGB and sine wave of audio are odd functions as given in their Fourier series. This means their harmonics occur at fundamental frequency then 3x, 5x, 7x, etc. multiples and, by extension, all of their noise. In reality, some noise appears at even harmonics and spread across the whole bandwidth and such 'non-ideal noise' is greater with lower quality signal generators.

Ideally, the power at each subsequent harmonic is less than the one before (is more negative) and we see that on the INPUT. From horizontal sync, highest noise at 15.7 kHz then declines at 3rd harmonic of 47.1 kHz, 5th harmonic of 78.7 kHz and 7th of 110 kHz. On the OUTPUT side, noise gets worse (less negative towards 0 dbV) and this because the filtering is better at lower frequencies. Is how 7805 filtering works so not surprising.

The 32.0 kHz audio sampling frequency noise is much more than I ever expected. It created 'intermodular distortion' with the 2nd harmonic of sync frequency (31.5 kHz) since they sit so close together. Noise at nearby frequencies creates more noise and adds together (in the rms sense) at same exact frequencies. I doubt the audio sampling is intended to be a symmetrical signal, meaning it has odd (96.1 kHz, 160 kHz) as well as even (64.1 kHz, 128 kHz) harmonics and we see all those. I think the other kHz noise peaks are all from distortion with horizontal sync.

The 60 Hz vertical sync and its 30 Hz framerate would matter too on the 120 Hz AC-to-DC noise but far too low to matter above 1 kHz.
I later noticed that only my Japanese 1CHIP and 2CHIP consoles have the relatively expensive 1000uF capacitor for low frequency power filtering. Online diagrams confirm NTSC and PAL lack this. Unsure if Japanese Jr model has.

PSUs being equal, NTSC has 20% less low frequency voltage ripple than PAL due to 60 Hz being 20% greater than 50. PAL higher voltage has advantage of getting away with thinner cables due to less current for same amount of power drawn from the outlet.
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Re: SNES PSU

Post by NewSchoolBoxer »

Sirotaca wrote:Hopefully I'm doing this right.
https://imgur.com/a/uVfMhuM
Not much to talk about below 10 kHz. There are peaks at 15.7 kHz (horizontal sync frequency), 32 kHz (audio sample rate), and their harmonics, plus a small peak at 22.6 kHz that disappears after the 7805. Otherwise the input and output sides of the 7805 look more or less the same.

Unfortunately, Nintendo used some dumb security screws that I don't have a bit for, so recapping the original power supply will have to wait. I'll pick up a driver next time I do an order from Console5.
The 22.6 kHz peak is interesting. A tiny 0.14mV rms at -74 dbV with no harmonics that 7805 able to filter to the -100 dbV noise floor. Nothing in the console is creating that. Something in your environment but hard to say what. I'd guess is the high voltage flyback transformer in your television that would surely run above 15.7 kHz sync and likely above 20 kHz audible limit but below 100 kHz for optimal efficiency.
Spoiler
Image
Image
I opened my official NES PSU. One of two plastic beams was already cracked open. Is purely a transformer with no R or C. I suppose not shocking since the NES console would have the rectifier and filtering but you'd expect some form of overvoltage or overcurrent protection.

The 15 in the MUK040-15 must refer to the max amps, considering I found a listing for a "HIKARI MUK040-21A" at "120VAC- 13.8VNL" (no load voltage). I'd expect a 15A transformer to be higher than 13.8VNL but I don't exactly want to put multimeter probes on and try.

Seems Nintendo expected typical load from console to bring voltage down to 9VAC. The 1.3A max listed on the adapter is probably the max that the copper wiring can hold.
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Re: SNES PSU

Post by Sirotaca »

Forgot to mention it before, but I should note that this console has additional 10 uF ceramic bypass caps on some of the major ICs (S-CPUN, S-APU, all three RAM chips) that I added to try to reduce some high-speed noise in the video output that manifested as some light jailbars when turning my OSSC's LPF up above the default 9 MHz. (It did help noticeably.) It also has one of marqs' de-jitter boards and a 220 nF C11. I'd have done the testing with a more stock console, but my only completely stock SNES is my childhood SHVC-CPU-01 with a bad PPU1, which probably wouldn't be very representative either.
NewSchoolBoxer wrote:The 22.6 kHz peak is interesting. A tiny 0.14mV rms at -74 dbV with no harmonics that 7805 able to filter to the -100 dbV noise floor. Nothing in the console is creating that. Something in your environment but hard to say what. I'd guess is the high voltage flyback transformer in your television that would surely run above 15.7 kHz sync and likely above 20 kHz audible limit but below 100 kHz for optimal efficiency.
Nah, the TV wasn't even turned on when I was taking those measurements. It definitely seems like it's coming from the Triad, because it doesn't appear when using the Nintendo power supply.
NewSchoolBoxer wrote:When you're done RGB bypassing, is it normal to leave the steel shielding/heatsink off like this or put it back on? The wiring addition, which is not coax and has effectively zero shielding both to block EMI and prevents its own EMI from spreading, is concerning, more so if any steel shielding that protects against low frequency EMI is removed.
The SNS-101 doesn't have any shielding on the underside, only on the top covering the portion in front of the cartridge slot. Mine has not been removed.
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Re: SNES PSU

Post by NewSchoolBoxer »

That's really smart to add bypass capacitors on the critical ICs. I saw a writeup viletim/Tim W. did for adding capacitors to TurboGrafx-16 for this purpose but he seemed to pull values out of thin air versus being scientific like you were. I liked his explanation that went about: uF capacitors were comparatively more expensive in the 90s and didn't come in ceramic.

I'm happy your advanced modding work could preserve the heatsink. Snes Jr. shielding is still pretty minimal but I get it as a budget console late in SNES life.

De-jitter mod, would it exist without OSSC? I guess I'm being rhetorical. I'd like to be scientific on the C11 discussion where no one makes the greater point that it's the setup circuit for the Master Clock or considers replacing the crystal oscillator. Testing on modded consoles is still valuable as the best to what we can achieve today.

I thought I was smarter than I was for the 22.6 kHz noise origin. Thanks for the answer. My basic understanding is low voltage switching PWM runs at 500 kHz to 2.4 MHz and 100V+ will go into low kHz. It could be a product of intermodular distortion. Switching PSUs are complex and contain more than one fundamental frequency.

I wanted to document all the distortion between horizontal sync and audio. I think Shure's site has a really good and accessible explanation. Can see basically every peak in your graphs is the result of their interaction. I presume the slight inaccuracy of the expected frequency at higher harmonics is from 60 Hz interaction, else Master Clock drift that gets corrected in non-RGB video output from the colorburst:

Image

I'm a big supporter of 2.5-5V TTL over 300mV 75 ohm sync where you have the choice for being more noise resistant and what rest of world uses. Here though, the high voltage sync is more damaging since distortion is proportional to the square of the signal's power. For a 10x voltage increase, I think equates to +17 dB more distortion.*

Wait so is PAL less noisy for having +12VDC instead of TTL csync? DC voltage produces no EMI and DC current's magnetic field doesn't either unless rippling is huge. Horizontal sync from composite video and luma still exists.

My rechargeable 9V batteries officially got lost in the mail. New shipment coming next week.
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