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I have a small electric table gramophone, it uses a induction motor (hmv 24A) but I am, as of yet, unsure if it works, I want to test and use this machine but how would be the best way to try it, how could I ground the motor, it currently has the old style plug on it and it is ungrounded, all the wiring looks good
how do you test them??
Testing a electric motor.......without blowing the house up
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kirtley2012
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Chuck
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Re: Testing a electric motor.......without blowing the house
I would examine the motor first and try to
figure out what kind of overall shape it's in.
Can you see the coils? If so, do they look
burnt or otherwise ruined?
How's the cord?
You can always power up the motor in series
with a small fuse such as maybe 5 amps or
so. That way, if the motor coil is shorted
or otherwise no good, it will just blow
that fuse.
If you have an ohm meter, look at the coil
resistance. It won't be much, maybe 10, 15,
20 ohms or so, but if it says ZERO ohms
or .7 ohms, or some such thing that might be telling you that it's toast. If it reads infinite ohms, that means it's open, and in that case the motor will do nothing.
Another thing I have done is to take the item
to be tested, and put it in series with a
100 watt lightbulb. That way if it's a dead
short, all it will do is light the lamp.
Where as, if it's any good, most likely the
motor will start turning and maybe the lamp
will glow a bit dimly.
If it passes that test, then try it with
full power by removing or shorting the lamp.
So, use an extra small fuse or a lamp and be
safe.
Stand back when you first turn it on
because if it goes POOF and sparks fly, you
don't want your face down in there.
Be safe, use a good cord. Be careful.
Be thoughtful. Especially over on the east
shore of the Atlantic ocean, where the mains
voltage is 220 volts AC, 50 cycles.
That can hurt you or start a fire.
Over here on the western shore, we commonly
use 120 volts AC 60 cycles, which is not
quite as aggressive as 220 volts.
People who do this sort of stuff all the time
usually have a Variac around. That is a
variable transformer that has a knob on it
that allows the voltage to be reduced.
Start low at first, then work higher.
Guys who restore old radios use those all
the time.
Be careful and use common sense.
I know that you have some of that!
Chuck
figure out what kind of overall shape it's in.
Can you see the coils? If so, do they look
burnt or otherwise ruined?
How's the cord?
You can always power up the motor in series
with a small fuse such as maybe 5 amps or
so. That way, if the motor coil is shorted
or otherwise no good, it will just blow
that fuse.
If you have an ohm meter, look at the coil
resistance. It won't be much, maybe 10, 15,
20 ohms or so, but if it says ZERO ohms
or .7 ohms, or some such thing that might be telling you that it's toast. If it reads infinite ohms, that means it's open, and in that case the motor will do nothing.
Another thing I have done is to take the item
to be tested, and put it in series with a
100 watt lightbulb. That way if it's a dead
short, all it will do is light the lamp.
Where as, if it's any good, most likely the
motor will start turning and maybe the lamp
will glow a bit dimly.
If it passes that test, then try it with
full power by removing or shorting the lamp.
So, use an extra small fuse or a lamp and be
safe.
Stand back when you first turn it on
because if it goes POOF and sparks fly, you
don't want your face down in there.
Be safe, use a good cord. Be careful.
Be thoughtful. Especially over on the east
shore of the Atlantic ocean, where the mains
voltage is 220 volts AC, 50 cycles.
That can hurt you or start a fire.
Over here on the western shore, we commonly
use 120 volts AC 60 cycles, which is not
quite as aggressive as 220 volts.
People who do this sort of stuff all the time
usually have a Variac around. That is a
variable transformer that has a knob on it
that allows the voltage to be reduced.
Start low at first, then work higher.
Guys who restore old radios use those all
the time.
Be careful and use common sense.
I know that you have some of that!
Chuck
"Sustained success depends on searching
for, and gaining, fundamental understanding"
-Bell System Credo
for, and gaining, fundamental understanding"
-Bell System Credo
-
kirtley2012
- Victor IV
- Posts: 1607
- Joined: Sat Feb 11, 2012 3:10 pm
- Personal Text: Buyer of broken things
- Location: North Shields, UK
- Contact:
Re: Testing a electric motor.......without blowing the house
Thanks
I put a plug on it, put two fuses in between it and the motor runs like a charm!!, however, the arm has a open coil, there is no response from it, as you may know, there are hundreds of winds of very fine copper wire within these arms, and they are a real pain to wind and repair! considering this is not the original arm from this deck and the tracking is about 1" out, I might aswell just replace the arm with a hmv one, does anyone know where to get one of those (cheaply?)
I put a plug on it, put two fuses in between it and the motor runs like a charm!!, however, the arm has a open coil, there is no response from it, as you may know, there are hundreds of winds of very fine copper wire within these arms, and they are a real pain to wind and repair! considering this is not the original arm from this deck and the tracking is about 1" out, I might aswell just replace the arm with a hmv one, does anyone know where to get one of those (cheaply?)