ac/dc adapter Question

[9two5247]

Hello, i have a cassette player/recorder requiring 12 volt 5.2 watt ac/dc adapter. i do not have this exact one any more.

the unit specs are: (11-15 volts) 5.2 watts


My question is: Will a 12 volt / 800 Ma (9.6 watt) AC/DC adapter damage this device? it powers on and works?

i also have a 12 volt / 1 amp that powers it up also? Thank you for your replies!

 

[MrAl]

Hi,

If your recorder has a wall wart that was regulated at 12vdc then you may need that type again, but since you say the spec's are 11 to 15vdc then possibly the regular wall wart will work too if the voltage stays less than 15 volts. Check to see that the voltage never goes above 15 volts when it is operating.

 

[9two5247]

"wall wart"? You do mean at the end of adapter wire plug, correct?, so you are saying if the plug stays below 15v im good?

 

[9two5247]

I am getting 16.5 volts dc at end of adapter plug?????

 

[mramos1]

You could drop a couples diode inline and kill about 1.4VDC. Measure it though.

 

[9two5247]

"You could drop a couples diode inline and kill about 1.4VDC. Measure it though."

Suggestions on diode size? Are you saying to just put in wire between adapter and plug end? i have some of that stuff kicking around. TY

 

[mramos1]

Drop 3 inline with the positive line and take a reading with the meter.
Will try to do this fast in ascii. + is plus side, - is minus side.

Power/transformer end
-------------------------------------------------|------|
+++++++++++++++++++++++++++++++++++ >| >| >| ++++|------|  Plug
                                    3 diodes

Note sure where you are located, but a local Radio Shack should have .5 amp diodes I would think.

 

[MrAl]

I am getting 16.5 volts dc at end of adapter plug?????

Hi again,


Yes, that's a little too high according to the spec's of the recorder. As mramos said, you can use a few diodes in series to drop the voltage a little bit. With three diodes in series, you'll drop roughly 2.1 volts which will leave the recorder with 14.4 volts which is better.

If you dont have any diodes laying around but have some resistors, let us know what values you have and we can tell you if they will work or not. You can order diodes on line if you like, and for this application they would be very very cheap too, around 10 cents each. Diodes like 1N4001 would work fine.

 

[9two5247]

Hello everyone, (1) Okay, I found the diodes and got it down to 13V range. that seems easy enough to do. this particular adapter says 12V output and its showing 16.5V. we already know that and I can now drop it down with your help.

(2) I found another 12V adapter that is putting out 13 Volts on my meter. It is rated at "12V - 1000mA" however as far as I can test it is showing 1.5 Amps out? Trying not to be to confusing here but im not close to the 5.2 Watts recommended for the device. The original adapter I posted I cant even get an Amp reading on my digital volt meter but is says 800mA on the adapter

In a nut shell I can now get a close enough voltage reading, however will the wattage being up to 10 Watts or more damage this device according to Ohms law/Watts law?

Thank you all very much for your input

 

[Vizier87]

it might or it mightn't. one thing's for sure, the current output of your adapter is approx 0.8A, your recorder requires around 0.4A. just for safety, place a fine tuning pot in series with the wall wart output, start from say 100 ohms, reduce the resistance (probably it'll just need 5 ohms... ) until you get it functioning the way you want it to.

 

[9two5247]

TY Vizier87, good idea! I only mess around a little with electronics so im basically a novice but i enjoy fixin things and understanding stuff like this. So i will go ahead with this and keep you all updated. ty to every body and Have a GREAT DAY!

 

[MrAl]

Hi,

If you use a pot it will have to be rated for at least 2.5 watts. A more common 0.5 watt pot may burn out with some settings.
Note that a 3 ohm resistor will drop the voltage down by about 10 percent.

 

[Vizier87]

If I were you, I'd guess that the recorder regulates both current and voltage.. But that's just me.

 

[colin55]

If you are getting a reading of about 12v to 13v on the output of your "power supply" the circuit will be taking the correct amount of current and there is nothing you need do. Putting a pot "in line" is senseless. You will just negate the effect of smoothing provided by the "power supply."

 

[Vizier87]

Actually I wouldn't put the pot myself, but since the OP seems to wanting to be very careful about the whole thing.. oh well. like I said, I believe the recorder circuitry has regulation on both input voltage and current.

 

[3v0]

Provide the correct voltage and you do not have to worry about the current. Use a supply that can provide at least as much current as required by the device.

The current listed on the wall wart is the max possible. The device it powers will draw what it needs and no more.

Dropping the voltage with diodes is the better solution because the drop they provide is independent of the current or voltage.