Cant get a voltage reading off an working AC/AC Adaptor with a multi meter ?

[coffee_king]

Would anyone happen to know any reason why I cant get a voltage reading off an AC/AC Adaptor by touching the inside and outside of the pin with a UNI-T UT30B multi meter, even though it works perfectly?
I just want to know which is positive and which is negative as it doesnt state it on the AC/AC Adapter or on the appliance.

I can get a reading on all my other AC/DC adapters fine.

Thanks in advance
UK

 

[BobK]

If it is AC / AC there is no positive or negative, it is AC - alternating current.

And you you are using the DC setting on the multimeter, it might very well read 0.

Try reading it on an AC setting.

Bob

 

[coffee_king]

Hi BobK
Thanks for your response.
OK, thanks for that.

What I am plugging it into though (An in ear monitoring system to be used on stage with a band) states
AC/DC 12v 200mA

It works with the AC AC adaptor though.

Also it lights up and looks like its working with a regulated AC/DC Adaptor set to 12v
Input 230V 50Hz 10w
Output 3, 4.5, 6, 7.5, 9, 12V (DC Symbol)
500mA 6VA Max
With the centre tip as positive

but it doesnt actually function correctly.

Can anyone explain in layman's terms why this might be please?

The image of the AC AC adaptor in my initial post does work with the unit, but what I actually need are a couple more power supplies to run the exact same units that currently dont have any with them.

 

[shrtrnd]

I had a few of those multiple voltage adapters. The biggest problem I had was that the switch itself sometimes
wasn't fully aligned in the right position for the voltage I selected. You might wiggle the selector control a little
to see if you can get the correct voltage. Otherwise, I would assume the adapter went bad. (And get a new one
before the band goes on-stage).

 

[BobK]

If the unit operates off AC or DC it has a bridge rectifier inside and it can take AC or DC with either polarity. Did you check the output of the 12V DC adapter with your multimeter? If the voltage is right, I don't see why it would not work.

Bob

 

[coffee_king]

Hi Bob
Yeah the other 12v DC one shows as the correct voltage with the multimeter, its turn the unit on, but then it makes the input volume level stick at full volume and you cant get any sound out of it.
Really weird.

 

[Alec_t]

its turn the unit on, but then it makes the input volume level stick at full volume and you cant get any sound out of it.

Sounds like the unit is faulty.

 

[coffee_king]

Nah, Ive got three in ear monitor units all bought at seperate times, all the same brand and model. They cant all be faulty.

 

[Audioguru]

If you used the wrong adapter to power them all then probably now they are all damaged.

 

[BobK]

There is actually a big difference between powering it with 12V AC and DC. After going through the bridge rectifier, the AC supply nearly 16V DC, whereas the 12V DC input will result in less than 11V DC.

I suspect that difference is why it is flaky.

Bob

 

[davenn]

If you used the wrong adapter to power them all then probably now they are all damaged.

What I am plugging it into though (An in ear monitoring system to be used on stage with a band) states
AC/DC 12v 200mA

if that is really correct, then there shouldn't be a problem .... show us a photo of these units

and does it stat on it what the polarity is supposed to be ??
you only commented on the plugpack

 

[coffee_king]

Hi
No it doesnt state the polarity on the unit. (Image attached)

I did actually state what was on the unit in my original post.

 

[KTW]

Have you tried testing with the negative meter lead to a known ground?

 

[coffee_king]

Have you tried testing with the negative meter lead to a known ground?

Can you advise exact steps of how you do this please?

 

[KTW]

Take the black lead from your meter and place it on something that is known to be grounded like an electrical box or cold water pipe then probe the inside and outside of the barrel plug with the red lead.

 

[coffee_king]

Hi
Using what selected on the multimeter please?
Thanks

 

[KTW]

You are testing for 12 volts AC so set your meter to the next number above 12 on the AC voltage scale.
It could be 40 or what ever is greater than 12 on your specific meter.

 

[BobK]

The 12V is likely just the output of a transformer and isolated from earth ground. You can measure the 12V AC on the ac scale by using either lead on the barrel and the other on the inside.

But we are way past that anyway. The device works on the 12V AC adapater. And I already explained in post #10 why it might not work on a 12V DC adapter.

Bob