Been having some minor problems with my DAB radio.

 

On testing the mains  adapter for my DAB radio, I've found that the output is considerably off-spec.

 

The label on the adapter says it should deliver 9v, 1.5a (Which is exactly what the radio is expecting), but the multimeter showed 9.3v and an average of 0.3 amp, varying 0.1 to 0.5a on a second by second basis, even through the tester's probes were well planted.

 

When powered-off, the secondary circuit resistance eventually resolved from high to a lower figure of 4 K Ohm which was rock steady. The primary circuit came in at 2 M Ohm.

 

I also noticed that my mains supply was arriving as 245 volts, i.e. at the top-end of the UK Supply limits i.e. 230 +10% / -6%, whilst the adapter input was rated at 230 v, 0.42A.

 

I've never seen the output amperage of an adapter dance around like that before.

 

Is it faulty  ?

 

Should I be testing differently ?

 

If I do have to replace it, should I go for one with a rated input at 240 volts ? (The radio manufacturer's replacement offering, by ATL, China, (Of course !) is rated the same as my existing unit i.e. 230 v).

 

Nick

 

 

Don't you have to check amps with the device connected - so circumstances the cord and place in series

Don't you have to check amps with the device connected - so circumstances the cord and place in series

 

I hope that's what he did and not just short out the power supply with the meter  :peek:

Don't you have to check amps with the device connected - so circumstances the cord and place in series

 Ideally, but it was connected to a 10 amp drain on the multimeter, so I would have thought it would have zoomed up to its limit of 1.5 A and then got considerably hot and bothered trying to reach 10 Amp . . .; and  going pop in the process if I didn't desist in time. But it didn't.  I'm listening to the radio at the moment, powered by the adapter, no issues.

 

N

Edited 7 April, 201610 yr by Clunkclick

 Ideally, but it was connected to a 10 amp drain on the multimeter, so I would have thought it would have zoomed up to its limit of 1.5 A and then got considerably hot and bothered trying to reach 10 Amp . . .; and  going pop in the process if I didn't desist in time. But it didn't.  I'm listening to the radio at the moment, powered by the adapter, no issues.

 

N

It doesn't really tell you anything by putting a dead short across it. If it was a simple transformer then yes it may have just provided max current, but my guess is that you just upset it and this is why you were getting low readings

Trouble is how do you take a reading on the secondary cicrcuit without cutting the cable when the power cable is constructed such that it is  moulded to the mains adapter at one end and moulded to a jack pin at the other end. If you try to break open the connector to insert a pair of tester probe pins you break the negative side of the circuit at the slightest movement. ?

 

Afraid I haven't got an induction device.

 

 

 

 

Nick

Make up a lead with a male dc Jack one end and a female jack the other, split the cores out of your test lead and test with ammeter in series, jobs a good'un.

OH FFS!!

Does it power the radio correctly?

If yes, does it blooming well matter?

 

And the figures on the unit are the maximum, not the actual in use.

Edited 9 April, 201610 yr by Llanigraham

Is your meter calibrated or the battery low as this will give incorrect readings.

What meter

How did you make it apply a 10a drain? That's well over the adapter rating so you've probably now blown it up.

A lot of supplies now are switch mode so will behave differently to transformer + rectifier ones. The radio might regulate the voltage in, so being slightly over volts is fine. Maybe really strong noise from the psu could come out in sound, or cutouts vould switch off the radio, but else I'd guess it works or doesn't.