AC adapter question

[+-^CrossBow^-]

Okay...so some of you might know that I have an X-eye. However, when I got it, it didn't come with its original power supply. So, all this time I had been using a Genesis 2 power supply with it. It worked fine, however the X-eye did exhibit some odd issues from time to time such as CDs games locking up, or taking a long time to init the games..etc.

 

For those that are curious. The Genesis 2 power supply is a 10v@.86amp supply.

 

The Eye says it needs a 9.5v@1amp supply.

 

So today while I was at a flea market I found an ac adapter spec'd at 10.5v@1amp. I went ahead and picked it up thinking I could use it for the X-eye. Even at a volt above that spec'd on the X-eye I didn't figure there would be any problem.

 

so my question is this:

 

What would the rating on this PS normally be without a load on it? I ask because I tested the adapter upon getting home and while the adapter states 10.5v on it..I get just under 16v when I metered it out without a load. That seems a tad high to me? If it is too high, what might cause an AC adapter to output higher than it is rated to? I did take the adapter apart to look for anything obvious but to be honest it is clean in there and looks hardly used.

 

I did go ahead and try it on the x-eye and the x-eye works just fine with it. Better than before honestly. But, I have noticed two things that don't happen when using a Gen2 power supply on it.

 

One is that only when using a cartridge in the X-eye and not the CD portion, there is a very audible hum coming through when the game starts up. If you play a Sega CD game or use the CD player functions, this hum isn't audible at all.

 

The second thing is that using this power supply on the X-eye, the X-eye itself gets very very very warm about a half inch above the cart slot. It does get warm with the Gen2 power supply as well, but not as hot as it does with this one. I'm going to assume the extra 1volt above the rated need for the X-eye is causing this?

 

So...what do you think? Is the nearly 16v output without load on that supply too high when it clearly states it should only be 10.5v? Should I go ahead and use it on the x-eye since the x-eye doesn't blow up using it? At least..not yet? What about that hum? There is a 1inch piece of ferrite around this newer power supply so what else would cause the hum? Too much juice...even an extra volt?

 

In short...what the hell do you think?

[jsoper]

Make sure that new supply is DC output not AC. If not, you're asking for trouble, even if it works at first.

 

EDIT: Also even if DC output, it might have some AC voltage leaking through which would explain the hum. Do you have a multimeter to check?

Edited January 7, 2008 by jsoper

[+-^CrossBow^-]

yes i have a DMM to check it with. What, where, and how should I check for this AC leakage? As I said, opening it up all the solder points looked good as did the 4 rectifiers that were inside next to the cap.

 

What about that near 16v reading from the adapter tip when plugged in but not under load?

 

Also, why would the hum only be audible when in standard Genesis mode and not when the Sega CD portion kicks in to play a CD game?

 

You don't think that extra volt will be a problem right, since the x-eye has some pretty decent voltage regs in them?

[+Stephen Moss]

yes i have a DMM to check it with. What, where, and how should I check for this AC leakage? As I said, opening it up all the solder points looked good as did the 4 rectifiers that were inside next to the cap.

 

What about that near 16v reading from the adapter tip when plugged in but not under load?

Ther are two types of supply Regulated and Unregulated, a regulated supply would output the rated voltage off load, and unregulated supply will output a higher than specified voltage when off load, how much higher veries but is generally a third, ie an unregulated 9v DC supply will typically output 12-13 volts off load.

Unregulated supplies use a very crude regulation method of regulated that relies on the regulation of the transformer, basically they use a transformer with a rated output current which is less than that specified, the extra current drawn results in the output voltage of the transformer dropping and thus you get the specified voltage.

For this reason you should not us unregulated suppies in units that use less current than that specified on the adaptor or the input voltage will be to high.

Also, why would the hum only be audible when in standard Genesis mode and not when the Sega CD portion kicks in to play a CD game?

Do you mean the hum is comming from the adaptor, the system or is it comming from the system via the audio lead to the tv?

You don't think that extra volt will be a problem right, since the x-eye has some pretty decent voltage regs in them?

Provided that the x-eye does not use the the incomming voltage directly and regualtes it down you will not damage anything directly through over voltage reasons however 1 volt at 1 amp equals and additional 1 watt of power the regualtors have to dissiapate which is why it is will run hotter than normal. This additional extra power load could damage the regualtors over time if they are not sufficiently heatsinked.

Many regualtors have inbuilt thermal shutdown and so their output voltage will drop to a only a couple of volts if they get to hot and will only return to normal one they have cooled again so you may find that after 15 minutes or so the unit becomes unreliable or stop working for this reason.

[+-^CrossBow^-]

thanks for the iniput! This is exactly the kind of stuff I was looking for.

 

The audible hum is not from the adapter or the system...it is coming from the audio out on the system and thus being heard through the stereo that I have my systems connected to. When using a standard genesis 2 power supply, this hum isn't heard when playing genesis games. And this hum is also no present when I play a sega cd game using the replacement adapter.

 

I have also played games using this adapter for nearly an hour and so far the system hasn't shut down on me. However, it did lock up once when playing a Sega CD game that I had let sit and just run in attract mode. It ran for about 20+ min before I noticed the redbook audio just up and stopped. That is when I discovered it had locked up. But it has only done it that one time.

[+Stephen Moss]

The audible hum is not from the adapter or the system...it is coming from the audio out on the system and thus being heard through the stereo that I have my systems connected to. When using a standard genesis 2 power supply, this hum isn't heard when playing genesis games. And this hum is also no present when I play a sega cd game using the replacement adapter.

The only possible thing I can think of is that more current is require when playing genisis games than the sega cd which results in a higher ripple voltage on the supply from the replacement power unit which is effecting the audio side for some reason. The reason you don't hear it when using the standard genisis supply is that either the transformer in the genisis supply has better regualtion, the genisis supply has a larger smoothing capacitor thus reducing the amount of ripple or the genisis supply is a regulated supply.

 

My advice when purchacing non genuine replacements power units is to allways purchase regulated supplied that can supply the required voltage and current, although regulated units are larger and more expencive you do usually aviod such problem by using them. Having said that 10V is not a typical voltage for a regulated power supply but you can probably get away with 9V espically if all the main voltages are subregulated within the unit it is powering and are 6V or less as older systems probably won't have low drop out regulators fitted.