Bridgeport boss 4 Spindle not turning

I have a 1984 Bridgeport Boss 4 three axis that has been sitting idle in storage for 2 years. I just pulled it out and tried to put it through it's motions and the spindle won't power up. I know the trick about making sure it has spindle oil so I don't think it's that. The axis' move fine, everything else powers up. when you try to turn on the spindle you hear a buzz from the electrical box.
any clues?
Thanks in advance

snipped-for-privacy@gmail.com wrote:
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Probably a sticking contactor. Possibly a corroded contact in one of the motor overload heaters. You might try (with the POWER OFF!!) going in the enclosure and working the contactors manually. Most of them have some way you can get a finger or a tool in there and pushing the magnetic armature to drive the contacts closed. Many have a rubber damper to absorb the thump when the armature drops out, and these can get sticky with age.
Jon

Thanks Jon,
I took some scotchbrite to the contacts as well as the fuse's to no avail. Where are the motor overload heaters?
Jak

snipped-for-privacy@gmail.com wrote:
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The heaters usually follow the contactor. Find the contactor for the head and identify the 3 leads in (generally from the main machine breaker or fuses. Then identify the 3 lines out which go to the overload relay. Check for power coming to all 3 connections on the contactor; loose wires do happen.
If you have the proper power coming into the contactor I would disconnect the 3 output wires to the overload, try to activate the spindle motor, and check to see if you have power passing through all 3 internal contacts to the output terminals you've disconnected. The reason for disconnecting the wires is to prevent a false reading on any of the terminals which can be caused by power flow through the motor. If all you get is buzzing from the contactor at this point you may have a bad coil in your contactor.
If you find you have a proper connection through the contactor then replace the 3 wires and disconnect the 3 output lines at the output of the overload relay and check for a proper current path through it. If this should check good then check the lines and connections between the overload relay and motor and finally the motor itself (can you turn the spindle manually?).
If you could scan and post your electrical schematics it might help us understand your circuit. I understand there is a metalworking mailbox around here somewhere. Good luck.
dennis in nca

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    Just to be sure -- let me ask some questions:
1)    Can you turn the spindle by hand? If so, is it easy.
2)    If so, then is it possible that the belt has failed, and the     motor turning with no connection to the spindle may be the     buzzing which you hear.
    The overload heaters, if any one of them (there should be *at least* two, and possibly three) has overheated, it will open the wiring to the coils of the contactors to prevent *any* buzzing sounds. (Of course, if the heater coil itself has burned out, then you would get power only to two of the three phases, which would leave the motor buzzing.) If you can spin the motor by hand just before switching on the motor power, you should see the motor spin on up -- if the problem is loss of a single phase somewhere in the wiring.
    Note that at least my old BOSS-3 has a more complex contactor, actually two contactors mechanically interlinked, so one closes to run the spindle forwards, and the other closes to run the spindle in reverse. The mechanical interlink prevents both from turning on at the same time, and blowing all the fuses.
    Speaking of fuses -- have you checked the three cartridge fuses just before the master power switch on the back?
    The BOSS-3 (and presumably the BOSS-4, 5, and 6 -- the stepper motor axis ones) have each axis powered from a different phase, so if you can jog all three axes, you have full three phase power.
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    Possible.
    That is "the dropbox". Go to:
        http://www.metalworking.com
and read about how to use the dropbox (one of the click-on options).
    Good Luck,         DoN.