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Real Bull controller, adjusting the trim pots

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John Rudd:
If the overload current is set too high, there is a risk of damaging the motor!

The factory setup recommends locking the rotor for a minimum time to prevent this......

Gazz292:
I wasn't sure how else to apply a load to the motor, short of building some sort of dyno... which i guess if i anchored one side of the strap to the ways, and pulled on the other end with a spring balance i could kind of do.

I didnt want to take a cut as i had the controller board sitting right where the chips would fly, but these little lathes dont have that much torque i believe,

So.. should i lock the chuck then start the lathe up, and monitor the current? should it cut out fast, or is it a gradual reducing of power when the overload is reached.

Are these boards kind of universal?  i see unused 2 spade connections for F+ and F- next to a big resistor thats got a little warm in the past, i presume the F connectors would be field connections? not used on a permanent magnet motor i have... or was it just the motor braking resistor?
 
i kinda wish i could find the old board that i took out of this that provided the motor braking, so i could try and get just that part working again, i have the little board in the base of the controler box that has the transformer on it and a relay and big wire wound resistor, amadeal call it a filter board, it has wires coming off it that i've taped up when i removed the other board, and a green connector thats no longer used, oh and it takes the tacho pulses and sends them out to the display,

But here is the main board i have.
 

Gazz292:
Blimey, what a lot of stuff i've forgotten over the past 9 years,

Been searching for things relating to this board and the real bull lathe etc,  and one of the google searches was to this forum, a post i'd put up when i was last having problems with the lathe in 2011, that was when i disconnected that bottom 'filter board' as it was causing a big resistor on the main board to overheat, and kept cutting power to the motor, so turns out there is no auxiliary board i keep mentioning, it's all down to that lower board with the transformer on it just for the tacho it seems.

And.... it turns out that it was me who twiddled the trim pots last  :doh:

I also wanted to put motor braking back onto the lathe 9 years ago... but never got round to it, story of my life.

John Swift did a doodle for me back then of how to wire in a relay to put a resistor across the motor wires when power was off, and i even thought up an alternative way to do it using the inhibit connections on the main board and wiring it to some of the unused switch contacts in the motor reverser switch, so it'd kill power if i ever moved that switch with the lathe running for some reason.


I've also been thinking of putting in a computer fan to blow into the motor all the time the lathe is powered up, others have done this before as they found the motor cooks if you use it at low speed for so long (i am looking for a slightly larger driven gear for the headstock, i believe it's 31 teeth stock, so i might get a 33 or 34 tooth gear on there, and that might help keep the motor running faster for low spindle speeds)

Would it be silly to get the 12 volt power for the computer fan from the 12 volt rail on the main controller board? i believe it's that big cooked resistor that is dropping mains to 12 volts for the boards functions, assuming it's 12 volts DC... there's a point near the max speed trim pot marked +12v, so i presume that will be DC there (but if not i can add a bridge rectifier)

I might also add surface mount led's to the empty solder pads for the power on and overload led's on the board, it looks like the resistors are present, so why on earth did they not add the led's... at least for the overload one.

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