Ac power adaptor on DC device

[sony mavica]

Hi I have a device that takes a adapter that has a headphone plug at the end  it says on the back DC 9v 300mA could I use a 12v ac 500mA adapter with it or will it break the device

[basinstreetdesign]

Hi.  Plugging AC power into a device asking for DC power is never a good bet.  Also 12 VAC has 17 V peaks.  That much overvoltage could do any amount of damage.  Of course, with my luck you could try it and it might work just fine just to make me a liar.  I think its a long shot, that's all.  Just sayin'

[mariush]

Hi I have a device that takes a adapter that has a headphone plug at the end  it says on the back DC 9v 300mA could I use a 12v ac 500mA adapter with it or will it break the device

You shouldn't.  At the very least you should use another DC rated adapter, not an AC output one.

But you could always open the product and see what it does with that DC input. Some products place a diode in circuit with the input jack for safety reasons, which means your AC input will be half wave rectified so it wouldn't hurt the product. others may die due to reverse / negative voltage of the AC input.
If there's a bridge rectifier inside the product, or you use a bridge rectifier to convert the AC voltage of the adapter to DC before going into the product's connector .. what's after that connector...  A product designed for 9v DC may use 10v or 16v rated input capacitors and a 12v AC rectified voltage can in some cases go over 16v

And then ... the product may use a tiny linear regulator to convert those 9v into 5v or 3.3v - there are linear regulators which can only tolerate up to a certain voltage, like 10-12v ... that would exclude the 12v AC/DC adapter, because even a 12v DC adapter may output more than 12v in some cases and kill the linear regulator.
And it's not just an issue of input voltage... could be a power dissipation isue.  let's say there's a 3.3v 100mA linear regulator in the product. With 9v input, the regulator would waste (9v-3.3v)x0.1 = 0.57w but with 12v input you have 0.9w of heat... this may cook the regulator, may discolor the plastics around that regulator, may make the regulator to "hiccup" (work sporadically) 

So there's no easy answer, if you want to risk it best chance is to open the product and analyze the input, see what the product is doing with it..

[sony mavica]

Hi I have a device that takes a adapter that has a headphone plug at the end  it says on the back DC 9v 300mA could I use a 12v ac 500mA adapter with it or will it break the device

You shouldn't.  At the very least you should use another DC rated adapter, not an AC output one.

But you could always open the product and see what it does with that DC input. Some products place a diode in circuit with the input jack for safety reasons, which means your AC input will be half wave rectified so it wouldn't hurt the product. others may die due to reverse / negative voltage of the AC input.
If there's a bridge rectifier inside the product, or you use a bridge rectifier to convert the AC voltage of the adapter to DC before going into the product's connector .. what's after that connector...  A product designed for 9v DC may use 10v or 16v rated input capacitors and a 12v AC rectified voltage can in some cases go over 16v

And then ... the product may use a tiny linear regulator to convert those 9v into 5v or 3.3v - there are linear regulators which can only tolerate up to a certain voltage, like 10-12v ... that would exclude the 12v AC/DC adapter, because even a 12v DC adapter may output more than 12v in some cases and kill the linear regulator.
And it's not just an issue of input voltage... could be a power dissipation isue.  let's say there's a 3.3v 100mA linear regulator in the product. With 9v input, the regulator would waste (9v-3.3v)x0.1 = 0.57w but with 12v input you have 0.9w of heat... this may cook the regulator, may discolor the plastics around that regulator, may make the regulator to "hiccup" (work sporadically) 

So there's no easy answer, if you want to risk it best chance is to open the product and analyze the input, see what the product is doing with it..

i do have a 9v dc adapter here but has the wrong connection

[JacquesBBB]

You can cut the connector from the AC  adapter and solder it to the DC one, but be careful to the polarity.