AC Adapter woes - GEN/SNES Decided to make a thread about this after being reminded of this crap browsing the consolized MVS problem thread. I've got a couple of these cheap "RETRO GAME!" AC adapters that have two plugs on them, and will work with an NES/Genesis/MD, or a SNES (supposedly.) If I use it on a few of my model 1 Geneses, there is a horrible audio hum that almost drowns out the game sound. Other Gens (all model 1s, that's what the plug fits) have even worse problems, but that could be compounded by issues with those particular systems. If I try to use the adapter on my model 1 Sega CD, it won't function properly, the tray opens very slowly, seems to have a lack of power. It won't bring the laser pickup assy up to even try and load a disc, even when the door does actually close. I gave one to my brother while I fixed the cord on his SNES adapter, and it worked fine until he tried to play FFIII (FFVI), and said it was giving him some lines on the screen, I think. Anyone have an idea of why these adapters are bad? Inside, they have the transformer, one large capacitor and four medium-sized diodes. I haven't popped open a proper adapter in a long time so I'm not sure what to compare that to. Perhaps there's some modifications that might get them working fine? Even just some insight on why they suck so bad? I've got another 9v adapter that has even less milliamps to spare, and it powers the Genesis or SCD just fine.
It's mainly because they are built badly, they are genereally unregulated, so that any draw over 1amp tends to drop the voltage and make the psu hot, there will also be a lot of hum as the capacitor can only smooth the ac ripple that much. If the device is drawing less current then the voltage tends to go up. You'd be better off chucking it in the bin and buying a decent 9V, 1amp (or greater), regulated power supply. The only good thing about these units is that they normally come with the correct bits for most consoles.
So, it's the transformer itself that sucks, then? Just thought maybe they skimped on parts instead of sheer quality, or a bad choice in capacitor. The main reason I wanted to get some of these crap supplies working is that they were, well, cheap (outrageously) and bought them to go with consoles just so I could unload a few. Cant justify spending money on single supplies or I won't make any profit (or break even, even) on the consoles since I'm sure the buyer won't care how much the power supply costs, unless they have to buy it themselves.
Depending on the intensity of the hum it could be that the transformer fails to supply the required current for the said console. If it's faint, it might be filtering issues. A stronger hum means the transformer is too weak for the load it's supplying power for. This regards only for linear power supplies. (transformer based)
Its most likely too weak brick, these thingies rarely output as much they have written on them.... you can make a fire when you use that brick with MD for little longer, after some time the plastic gets all soft and soon it will start burning
Nothing beats the original PSU. Just stick 'em all into a eight way switched extension socket and switch between the ones you want to use. That's what I do :nod: Even though it looks a bit untidy, it's perfectly safe (so long as you don't switch all of the PSU's on at the same time heh).
We've had many discussions about PSUs before. Don't forget that some consoles use AC output instead of DC (although fewer in the US, I believe it transpired). You want the right voltage and AT LEAST the current stated on the original PSU or the console itself. It goes without saying that you need the correct polarity, too! ;-) Most consoles have regulators so unregulated PSUs are usually OK. The simple answer is: don't buy cheap crap! I have to agree with the vote for using the original PSU. You can almost always pick up an original PSU for most consoles on eBay for very little money.
1. alecjahn's cheap PSU consists of a stepdown transformer, a bridge rectifier (the 4 diodes arranged in a diamond pattern) and a filter capacitor. This is the absolute cheapest possible design, is very noisy, but works. The parts are going to be also the cheapest parts the Chinese fab shop could source. Don't waste your time, they're crap. 2. Unregulated AC supplies DO normally output higher-than-spec voltages. This is because you are measuring them under no load! Once you plug them into your console, current is drawn and the voltage drops down very close to where it should be. 3. Even if it didn't, the consoles would work fine anyway. Almost all 80s/early 90s consoles (NES, SNES, Genesis, TG too I believe) have 7805 voltage regulators right at the DC input. They will accept any voltage between 7 volts and 35volts, and drop it to 5v for the console. This is why you don't have to worry.
I realize I should use the originals and blah blah blah blah. My main question, I guess, is whether there's any way to get these to be less crappy. If I can find a bunch of proper adapters for a reasonable price, I'll buy them. Until then... actually, until then, I just won't be able to unload any of these, as the adapters just aren't going to work at all. It's odd that it is stated they aren't putting out enough juice, when I can run the same MK1 Gen on a Sony 9v 650ma brick with absolutely no problems. Even with a Sega CD. Surely a loud HUMMMMMMMMMMMMM would be something different than just a lack of current. I did pick up a couple of sega 1.2a supplies at the flea market from one of my regular stops, but those will be for myself to use.
The HUMMMMMM implies something is very wrong with the power supply. We just stated that it's usually the linear power supply being not able to supply enough juice. It can also be bad filtering CAP on the supply or one of the diodes blown/disconnected on the rectifier bridge (would supply only half of the sine waveform, causing quite a noticeable hum.) While what marshallh said is very true, using these chinese knock-off PSU can lead into fire hazard due to overcurrent. One can safely assume they *never* meet the promissed spec. Also they come with humorous advice like the one I saw yesterday on these knockoff GBA SP/NDS power adapters: "THIS ADAPTER CAN USE IN MOST COUNTRIES(pal,NICS)" (They meant NTSC I suppose) "CONSTANT OUTPUT VOLTAGE 5.2v WITH SHORT PROTECT" (nothing more than what an decent switching power supply should do) "DRY LOCATION AND INDOOR USE ONLY" (sounds about right) "RISK OF ELECTRIC SOCKET" (YES, they said "risk of electric socket" this one was gold...) I would not trust an collection item into such a shoddy power supply.
