Isn't using an AC adapter with way higher current ratings harmful?

AC/DCdude17 · 2003-07-18T09:56:19+00:00

X-No-Archive: Yes The common rules for choosing a replacement AC adapter are match thevoltage and amp should be equal or greater than the original ACadapter. This makes perfect sense in theory, although the smalltransformer in AC adapters have a horrible regulation. A 12V AC adapteroften puts out 16 to 20V under no load and is designed to give 12V whenloaded to rated current. Once it's loaded to rated current, I^2R dropbrings the voltage down to 12V. If you have a walkman that takes a 4.5V @ 250mA and use a 1Aadapter, it will probably send out 6-8V with only 250mA of load. Thewalkman most likely has a linear regulator inside, so it should be ok ina short term, but higher input voltage means higher dissipation whichmay cause premature failure.

Jul 18, 2003 27 Replies

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DarkMatter 23 years ago

On Sat, 19 Jul 2003 20:39:43 GMT, "Mark" Gave us:

There are UL LISTED devices, and UL approved devices. There is a difference.

I'm not sure you knew how to decode them. From the above statement.

You would be surprised at what level of quality products are made there, apparently.

Now, you are talking about system integration. Many makers DO make sure their vended adapters are conformal. It would be like shooting one's self in the head, let alone the foot. I suppose it does happen, though. Just not in my company.

No. But nor do I believe that the adapter only put out less than one tenth its rating. Are you sure that it wasn't 750 mA out of 1000? That is out of spec as well, yet far more believable.

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DarkMatter 23 years ago

On Fri, 18 Jul 2003 13:44:31 GMT, "Mark" Gave us:

For LV power supplies, exactly.

There are HV supplies that are specifically "proportional" type supplies and are designed to be so.

Wall warts, and inline adapters should be regulated to a specific loading at a specific ripple figure at a given design voltage. I know of none that are of proportional type. AC-AC adapters are mere transformers in a box, and will of course, be limited by the capabilities of the transformer itself.

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Gym Bob 23 years ago

I guess it depends on your definition. Some call all units "AC adapters".

Ever think a simple question would get so hard to get an answer?....LOL

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Gym Bob 23 years ago

Have to agree with the DC output theory but he really didn't specify in his post.

It depends on the specific adapter and application and cannot be predicted here.

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Brian Oakley 23 years ago

Don't most devices that are designed to be used with wall warts operate over a wide (+/- 5 to 7 V) anyway?

-- Brian Oakley

"Jesus invited us not to a picnic, but to a pilgrimage; not to a frolic, but to a fight. He offered us, not an excursion, but an execution. Our Savior said that we would have to be ready to die to self, sin, and the orld." -Billy Graham

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Mark 23 years ago

I highly doubt your claim. what would be the point. If It has AC inside it would need to be UL approved. Also the Modem chipsets need 5V DC. Look at your power supply.

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Eric Palmer 23 years ago

I have 3 external modems all three are 12 VAC and will not work with a DC supply. Also a card reader for my mother-in-laws sewing machine is also 12 VAC. We have lost one and with a 1.5 Amp rating I have not found a replacement as most power supplies are DC. I could easy make one up but since the internals are 56K and externals 33K I no longer use them except to send and receive faxes as they have ring ID built in where internals do not.

All best Eric GW7MGW Ex VR2ZEP and VP8BKM looking forward to returning to use HF again.

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