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I have a SB9C that runs on a single phase, 3/4hp, AC, 120+/- volt motor.
Please school me on the advantage and process of going DC.
On Wednesday, September 1, 2021, 02:24:31 PM CDT, Ondrej Krejci via groups.io <okrejci@...> wrote:
I should like to know, out of curiosity, how many people run their machine tools on direct current or with universal motors as opposed to the general norm of alternating current and induction motors.
On Wednesday, September 1, 2021, 12:15:31 PM EDT, ART <twocan90@...> wrote:
I decided to go back and check my repair to the smoking switch, and I found the real problem.
The connection between the "tab" where the output wire from the switch connects to the motor was a riveted connection that worked loose over time. This loose connection generated heat which heated the wire and weakened the insulation on that wire causing a short to the ground wire which was touching it in the small space of the switch housing.
Hope that helps.
----- Forwarded Message -----
From: ART <twocan90@...>
To: SouthBendLathe@groups.io <email@example.com>
Sent: Tuesday, August 31, 2021, 04:44:02 PM EDT
Subject: Re: [SouthBendLathe] Switch Smoke
Carefully check for frayed or broken insulation on the wires that feed the switch.
I just had this exact same thing happen on my drill press. Upon opening the switch cover, I found the positive input wire rubbing against the ground wire. This is also the original switch, probably 20+ years old.
In any case I insulated the broken insulation and the problem was fixed.
You should also make sure that the jumper wire is the same size as the rest of the wiring.
On Tuesday, August 31, 2021, 04:31:30 PM EDT, Glen Ruch via groups.io <gw.ruch@...> wrote:
Perhaps the Motor Wiring Diagrams would be of use:
On 8/31/21 3:20 PM, Glen Ruch via
Depending on the connection, it is possible the circuit is
running thru the motor commutator thru the motor coil back thru
the commutator to the drum switch. The motor winding could be
read as a short circuit depending on how the Ohm meter is set.
On 8/31/21 12:37 PM, G K via
When checking continuity
with my voltmeter, I am showing a closed circuit between T1,
T3, and T2, T4. Is this expected, or is there an issue
within the motor?
On Tuesday, August 31, 2021, 08:43:13 AM CDT, Ray De
Jong via groups.io <dejongray@...>
The Jumper terminal screws may have
been a bit loose and arcing occurred and the
resulting heat build up probably fried the wire. I
have replaced many receptacles that fried not only
the lead-in conductor but also the inside of the
outlet, all from contacts losing their tension
an/or a loose connection
Working on the SB9
tonight, and smelled a little burn.
Flipped the switch off. looked around
and saw no issues. Flipped it back on
and pop goes the breaker, and smoke
from the switch. I believe the switch
is the original (1942) drum switch.
Unplugged it, and took the cover off
the switch, and the jumper was fried.
No idea why. I'm not an electrician,
but can use a voltmeter. Suggested
120 volt circuit. Furmas
R44, 6-terminal switch, Dayton 3/4 hp
I'm planning on pulling
it apart tomorrow and look for any
additional burned wires, but I do not
believe I will find any from a cursory
look. Then I'll wire a receptacle
directly onto the motor to see if
there are any issues there. If were
good there, I will re-wire the switch
and see what happens. Maybe some
chips got inside and caused a short.
Not sure. Any chance capacitor went
back and caused the short? The only
burn smell is in the proximity of the
switch, but that could be where the
smallest gauge wire (jumper) is