Maker Pro
Maker Pro

Wall Transformer Gone Bad?

V

VHarris

Jan 1, 1970
0
I have a 120v AC Class 2 Power Supply that is rated 12v 500mA DC
output. On the voltmeter, its output is ~20.4 volts. What typically
goes bad that causes such a high spike in the output voltage?
 
P

Phil Allison

Jan 1, 1970
0
"VHarris"
I have a 120v AC Class 2 Power Supply that is rated 12v 500mA DC
output. On the voltmeter, its output is ~20.4 volts. What typically
goes bad that causes such a high spike in the output voltage?


** Connect a 24 ohm ( 6 watt rated ) load.

See what happens.



............. Phil
 
V

VHarris

Jan 1, 1970
0
I don't have a 24 ohm load, but I connected a 150 ohm load and the
voltage across the leads dropped to 17.3 volts.
 
P

Phil Allison

Jan 1, 1970
0
VHarris said:
I don't have a 24 ohm load, but I connected a 150 ohm load and the
voltage across the leads dropped to 17.3 volts.



** Learn how to post.

The learn ohm's law.



.......... Phil
 
P

Pooh Bear

Jan 1, 1970
0
VHarris said:
I don't have a 24 ohm load, but I connected a 150 ohm load and the
voltage across the leads dropped to 17.3 volts.

Right.

So the wallwart is fine.

Graham
 
F

Fred Bloggs

Jan 1, 1970
0
VHarris said:
I have a 120v AC Class 2 Power Supply that is rated 12v 500mA DC
output. On the voltmeter, its output is ~20.4 volts. What typically
goes bad that causes such a high spike in the output voltage?

How does the AC power supply have a DC current rating? You mean it is
120VAC input with 12VDC @ 500mA output. This power supply is
unregulated, it's only function is line step-down, rectification, and
some filtering. The output DC voltage will be a function of loading,
settling to 12VDC with 500mA of current draw. If you need 12VDC at
lesser current, you will have to add an external regulator, or buy one
that has the word "regulated" on the label.
 
K

kell

Jan 1, 1970
0
Fred said:
How does the AC power supply have a DC current rating? You mean it is
120VAC input with 12VDC @ 500mA output. This power supply is
unregulated, it's only function is line step-down, rectification, and
some filtering. The output DC voltage will be a function of loading,
settling to 12VDC with 500mA of current draw. If you need 12VDC at
lesser current, you will have to add an external regulator, or buy one
that has the word "regulated" on the label.

Or put an extra load resistor in parallel with the load you want to
run, that will bring the voltage down.
 
Top