[Taz]

Newbee here. The wall wart charger for my rechargeable vacuum failed.
It's rated 24VDC 250MA. I decided to open it up and see what's inside.
Just a transformer, a capacitor and 4 zener diodes. Very simple
circuit. Anyways I made an educated guess that the capacitor had
failed, so I replaced it. Still doesn't work. I took out one of the
diodes and checked for continuity, one way go the other no go, I
assume it's ok and so are the rest. That only leaves the transformer,
so my question is how do I check transformer function? Can I use an
oscilloscope to check the transformer output? I am also wondering if a
scope can be used to look at line voltage directly (stick the probes
in the wall plug-hey I am just an amateur). Tnx

 

[Charles]

Newbee here. The wall wart charger for my rechargeable vacuum failed.
It's rated 24VDC 250MA. I decided to open it up and see what's inside.
Just a transformer, a capacitor and 4 zener diodes. Very simple
circuit. Anyways I made an educated guess that the capacitor had
failed, so I replaced it. Still doesn't work. I took out one of the
diodes and checked for continuity, one way go the other no go, I
assume it's ok and so are the rest. That only leaves the transformer,
so my question is how do I check transformer function? Can I use an
oscilloscope to check the transformer output? I am also wondering if a
scope can be used to look at line voltage directly (stick the probes
in the wall plug-hey I am just an amateur). Tnx

The diodes are rectifiers, not Zeners.

The transformer can be checked with a multimeter.

 

[bob]

If its looks like the transformer it may simply be the thermal overload
protection which is usually mounted right on the outer windings You can get
a replacement at radio shack check for the right temp
bob

 

[Meat Plow]

Newbee here. The wall wart charger for my rechargeable vacuum failed.
It's rated 24VDC 250MA. I decided to open it up and see what's inside.
Just a transformer, a capacitor and 4 zener diodes. Very simple
circuit. Anyways I made an educated guess that the capacitor had
failed, so I replaced it. Still doesn't work. I took out one of the
diodes and checked for continuity, one way go the other no go, I
assume it's ok and so are the rest. That only leaves the transformer,
so my question is how do I check transformer function? Can I use an
oscilloscope to check the transformer output? I am also wondering if a
scope can be used to look at line voltage directly (stick the probes
in the wall plug-hey I am just an amateur). Tnx

A simple voltmeter on the secondary of the transformer will tell you. Be
careful not to make contact with the primary.

 

[hr(bob) [email protected]]

A simple voltmeter on the secondary of the transformer will tell you. Be
careful not to make contact with the primary.

The thermal fuse looks like a small glass resistor in most cases, but
will read open-circuit in both directions if it has failed. You ned
to look at the secondary transformer voltage on the transformer side
of the thermal fuse to be sure it is the fuse that is defective, not
the transformer.

Unplug the transformer and check resistances also. If you measure the
line side resistance, it should be in the range from 10 -30 ohms, more
or less. The secondary resistance should be about 1/5th that amount,
as a rule of thumb.

The diodes are probably arrnaged as a full wave bridge.

H. R. (Bob) Hofmann

 

[Eeyore]

Newbee here. The wall wart charger for my rechargeable vacuum failed.
It's rated 24VDC 250MA. I decided to open it up and see what's inside.
Just a transformer, a capacitor and 4 zener diodes.

Wrong already.

Why did you think they are ZENER diodes ?

Graham

 

[clifto]

I took out one of the
diodes and checked for continuity, one way go the other no go, I
assume it's ok and so are the rest.

I bought a dozen eggs the other day and the container is leaking egg.
I took out one of the eggs and checked it for structural integrity and
it was fine. I assume it's ok and so are the rest. So where is the leak?

 

[JW]

I bought a dozen eggs the other day and the container is leaking egg.
I took out one of the eggs and checked it for structural integrity and
it was fine. I assume it's ok and so are the rest. So where is the leak?

42.

 

[clifto]

42.

And the student was enlightened.