Replacement AC adapter for SCART to component converter

As part of my quest to solve my SCART to component converter's buzz, I'm now looking to a different AC adapter. The reason being, the one it came with has a Euro-style plug, and the converter it came with fits REALLY REALLY loosely in the outlet. Seriously, it wobbles if you bump it. I'm thinking there might be some arcing that's introducing the buzz or something. So, I thought I'd find a local replacement with an AUS style plug . Here's the adapter's specs:

I assume that "PRI" and "SEC" are "input" and "output" in some crazy language? So that means I need an AC adapter that's 12 volts, 300 amps and... Is that suppose to be 3.6 watts? Anyway, I need an ac adapter with these specs right?

 

As long it has similar voltage, the same or greater amperage and the same polarity you're fine.

 

The outout is 12V DC with the positive lead on the center. If your new adapter is more than 300ma, its not a problem at all.
I find it funny when they use lines to express that the current is either DC or AC, but i guess it can be univerally understood by opposition to AC/DC which is english.

In my city there is a place where they sell electronic surplus and I usualy can find just about any kind of adapter for around 5$. The good part is they are usually quality adapters too, by opposition to the similarly priced you find on ebay directly from china. Maybe you have a similar place near you? Its like a large surface electronic parts discount store, I go there almost every week.

 

You could also try a better quality adaptor.

I am betting the one they gave you looks like this.



These are shit, the pins are too thin.

I use these ones instead, the pins are thicker and hold in the socket better.



Trial and error, the first type are only good for the bin.

Either that or go down to Jaycar and see what they have.

*Edit

I just tried mine (same power supply) and there is no buzzing.

 

They did send me that exact same converter I wasn't sure if I should avoid converter plugs entirely, just to be sure, like maybe the ac adapter is poor quality or something (the cord is really thin), but you say you're not getting any problems when using a better converter with the same ac adapter, so I could give a better converter a shot.

I've always found it odd that only the voltage seems to be important when it comes to AC adapters, and you can use amps much higher than the original without damaging the product. In humans, isn't it the amps that do the damage when someone is electrocuted and not the voltage?

 

The explanation to this is that the number of amp/milliamps written on the adapter is its current rating, not the actual amount of current that will flow. The actual amount of current being drawn into the circuit is determined by the load, not the ac adapter.
The amount of current that will flow depends of the Ohm law. I = V/R ( current = voltage/resistance )

So if you have a small circuit that draws 50 ma at 9v and you power it with a 1amp brick, this means that the amp will only be working at 1/20th of its capacity, you could then power other circuitry at the same time. This is also why a guitarist can power several effect pedals with only one AC adapter and a splitter.

 

To get electrocution you really need volts AND amps. Potential (volts) to overcome the resistance of your body (which is quite high) and current (amps) to generate burns and interfere with neural activity.

High-voltage low-current supplies (like static electricity) aren't dangerous, and low-voltage high-current supplies (like a car battery or an arc welder) are quite safe too. It's when you have both (mains, lightning, car ignition coil) that you have a problem.

Edit: Also, WRT the OP, "PRI" means "Primary" and "SEC" means "Secondary". This terminology exists because in the not-so-distant past, those wall warts contained conventional step-down transformers. The primary winding received power and the secondary winding output it. These days it's not so relevant because wall warts are mostly switch-mode power supplies now, and while there is a small transformer in there, it's not what produces the output.

 

Ah, I see, thanks MaxWar and RetroSwim!

I brought a new converter today, the plug still wobbles a little (I think one of the pins might be bent), but at least the power doesn't cut out now when it does. Some of the buzz has been eliminated, at least, the kind that appears when the plug is bumped. I think what I'll do is get one of those SCART audio splitters and see if grabbing the audio outside of the SCART converter makes any difference.

 

Sounds like you have a ground loop. The splitter likely wont help much as probably everything inside the converter box uses a common ground. Im not a specilist in ground noises but I have a behringer hum destroyer that i use. Its actually a stereo ground isolator and it works very well for some types of noise.

There are cheaper alternatives on ebay but i dont know if they will work as well as the hum destroyer.
http://www.ebay.com.au/itm/Stereo-G...=AU_Car_Parts_Accessories&hash=item3a6c4ebeb9

 

I'm not sure that I have a ground loop, since I could swear that I only hear the buzz when I'm playing SNES. Or maybe the SNES is more sensitive to ground loops?

 

12v at only 300amps? That sounds like thrift shop material, I doubt it's much trouble to find anything slightly used who won't need an adapter.

 

It could also be noise induction from any surrounding source, hard to tell.

Anyway, ground loops have always been mysterious to me, i do not understand them well but in my experience they can be just like that. You get a strong one with one device and nothing at all with the next.

If I connect my Sharp X68000 to my TV with a video converter i get the mother of all hum, it nearly drowns the audio.
Same setup with the Fm-towns, no hum.

Sometimes you just connect two grounded points of your circuit together and the hum disappears. I see it like sewer overflow. The ground connection is like the drain and you send down all kind of crap and unwanted electrical noise in it. Normaly this will go down the drain and disappear but because of "ground loops", the unwanted noise can reflow back into your circuitry somewhere else or taint signal with noise through induction or something.

As I said I do not understand the phenomenon very well and this is kind of how i explain it to myself.
Also seems that bad or broken connections will cause noise. They act like an antenna.

In any case, I still recommend one of those stereo Ground isolators. They are a very nice gadget to have for testing and troubleshooting, as well as getting rid of noise. My computer output has one in permanence otherwise I hear the computer "thinking". It makes all kind of digital noises, depending of what im doing. Like dragging a window kind of sounds like a Zipper etc... This type of noise does not vary with volume control, its always there.

 

Hmmmm, I think I'll clarify further what I'm experiencing, maybe see if it's the same as what you experienced.

To begin with, the noise isn't a "hum", like the kinda noise you hear when touch your sub woofer's plug with your finger. It's an electric "buzz" noise, and in the case of the SNES, it becomes louder when the picture is brighter. There was another thead where someone was experiencing the same problem, and they were able to fix it by using an official Nintendo SCART cable, but that didn't do anything for me. I don't think the TV is the cause, it I get the same behavior when the TV is off. I was getting a similar noise with my other consoles before I added the better plug converter, but now they're buzz-free. Like you said, you experience noise with some of your devices and not with others, so maybe a ground loop is what I'm hearing, and I need a filter like you said The reason why I thought that splitter might be a good idea is because it gets the audio before the SCART converter, while presently, I'm getting the audio via a mod I did to get audio out. I wanted to remove both the SCART converter as well as the audio mod from the chain and see if that changed anything.

 

Line hum is a pest in games consoles, because they typically have double-insulated power supplies, meaning the 0V point is derived from the input, and there is no connection to an actual ground. In addition, they rely on large capacitors to smooth the output from the power supply circuit, and these can wear out over time.

If there is ripple on the console's DC supply, this causes the 0V level to alternate slightly, so in the final output stage (for instance, the TV's internal amplifier for the speakers) the AC-like ripple passes through the coupling capacitor and gets amplified as if it were a real audio signal.

Replacing old step-down transformer based power bricks with modern switch-mode ones is a good way to control it, they provide a smoother DC output by design.

 

Hmmmm, I don't think the power brick is the cause of the buzz I'm experiencing. My Mega Drive sounds fine, but when I use it's AC adapter in my Super Famicom, I hear the buzz.

 

I know that Mega Drives (or at least Mega Drive II's) contain an LM7805 voltage regulator, which would do a decent job of smoothing out an uneven DC supply. I don't know much about SFC though, when I finish work I'll see if I can find a PCB photo.

 

You mean the console itself has components that help fix issues with power supply? Hmmmm... I had been suspecting the console, since all my other consoles that use the same SCART converter don't have audio buzz (at least, now that I have the better plug converter). I had been thinking about doing a separate audio out line (either RCA or optical) but I'm not sure if that would solve anything since I'm using an official SCART cable, which should be properly shielded.

Also, could a mod re-name this thread to "fixing Super Nintendo audio buzz" and move it to the repairs forum? That's kinda the new focus of this thread

 

Not so much to fix issues but for various engineering and cost reasons, many consoles have a 9V DC power supply, which gets dropped to 5V inside the console to suit the TTL signalling levels of the components.

 

I see, well let me know what you find out about the SNES' innards.

 

SFC/SNES has the same regulator.