Bad cap on motor question.

[mborgstrom]

Hey all,

Is there a way to test the capacitor on a 3/4 HP Shopsmith tool? Yesterday when I flipped the switch nothing happened. No hum, no sparks, only a momentary attempt to spin so short I'm not even sure it happened. I checked the breakers and the cord condition. I have not checked the switch yet but will shortly. Do these symptoms sound like a bad cap? If so is there a way to confirm?

These problems always seem to "pop up" around X-mas when "Santa's helper" is busiest:(

Thanks in advance,

Mike

The tool was made in 1954, same as me, but it is usually sharper and always faster!

[beeg]

I'd bet it's knot the capacitor but the contacts in the motor are dirty.

[mborgstrom]

Bob,

Thanks for the quick reply. Is there a way to remedy this? I have the motor free of the headstock and full visible at this point.

Thanks,

Mike

[billmayo]

I find it is normally the switch or a broken motor lead/wire on the 3/4 HP motors. I replace the power leads on most of the 3/4 HP motors as the wire insulation tends to break down/off on these older motors. I have not found a bad capacitor in over a hundred motor rebuilds. If the motor will hum, then I find it is the centrifugal switch points needing filing (start winding circuit open) or if no noise (no power to the run windings), then it is the ON/OFF switch.

[beeg]

Also read here.

While ya have it out, clean it up real good of the sawdust in it.

[JPG]

Bob,

Thanks for the quick reply. Is there a way to remedy this? I have the motor free of the headstock and full visible at this point.

Thanks,

Mike

I assume from its age that the capacitor is external to the motor shell.

That being the case, disconnect the capacitor leads and check for continuity from each lead to the linecord power(not ground) terminals.

If both capacitor leads are not connected to the power cord terminals then either the start switch(inside the motor) or the power switch is 'open'. I assume the power switch has already been eliminated as the culprit.

If both capacitor leads are connected to the power cord terminal, then either the capacitor is bad(not likely, but possible) or whatever was causing the start switch to fail to close has vanished! Secure the motor to the bench and try powering it up! If it still just 'jerks' slightly, the capacitor is probably at fault.

Assuming the 'not' condition above, try vibration(whacking the shell of the motor with a soft faced hammer) at various angles of attack and recheck the capacitor lead continuity again. If it now is connected, you just knocked whatever was preventing the contacts from closing loose.

Secure and try powerup as described above.

Let us know the verdict!


OH! Reconnect the capacitor leads prior to power up attempt!:o

Also if this does not 'get it back running', the next step is 'take the motor apart'.

[mborgstrom]

Hey everyone,

After reading the posts I took a closer look at the switch and discovered a barely noticeable broken wire. I reconnected and voila, back in working order. Now I just have to clean it up before reassembling the headstock. Any suggestions as to places to oil, lube or check before reassembly would be welcome.

Thanks all for the help. Santa's elf is back in business:)

Mike

[JPG]

Hey everyone,

After reading the posts I took a closer look at the switch and discovered a barely noticeable broken wire. I reconnected and voila, back in working order. Now I just have to clean it up before reassembling the headstock. Any suggestions as to places to oil, lube or check before reassembly would be welcome.

Thanks all for the help. Santa's elf is back in business:)

Mike

The movable sheaves (#10 oil) and the quadrant gear(graphite) and the carriage lock threads(graphite) and the speed control shaft bushing(oil) and the speed control outer ring gears(graphite) and the qui.............