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Real Bull controller, adjusting the trim pots

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Gazz292:
I have a real bull CJ18 lathe,

I bought it second hand in about 2012, and shortly after i got it one of the pcb's died... it was the board that made you turn the speed control knob to zero every time you wanted to start the lathe up, and braked the motor when turned off etc.

I removed and bypassed that board to get my lathe working again, i just followed something i read on the internet back then on how to bypass the board as they were unreliable.
i did plan on maybe adding back motor braking using a simple relay and resistor, but never got round to it,

I was actually glad to have got rid of the need to turn the speed knob to zero every time i start the lathe up, i just use the NVR switch like you would any other bit of machinery, and know that it'll start up at the last speed i used it,
i assume that if i was daft enough to change the direction switch with it running it'd go bang.


Anyway, this lathe has always needed its power board's trim pots 'tuning' so to speak, the motor will speed up when it's under load... i.e. it speeds up too much, as in too much current compensation or something,
and below 200 rpm it goes the other way, apply load and it'll reduce power to the motor, i'm only now remembering these issues as i've only just replaced the high - low gear with a metal one, the plastic one having lost low gear 4 years ago.. and the lathe being in storage for most of the time after.

I've read on another post that John Rudd knows these controller boards very well,

Can i get some pointers on which trim pots to twiddle and which ones to leave alone,

John Rudd:
Gazz,
Could you post up a picture of the board you have please?

The Sieg boards have 3 presets on the XMT series, while the KB Controls boards have 5 ( and their Chinese clones..).

Gazz292:
it deffo has 5 trim pots, i'll get a picture shortly.

Gazz292:
Here's the pcb

John Rudd:
The CL Trimpot sets the current limit (overload), which limits the maximum current (torque) to the motor. The CL also limits the AC line inrush current to a safe level during startup. The CL Trimpot is factory set to 1.5 times the full load rating of the motor. To increase the current limit, rotate the CL Trimpot clockwise (do not exceed 2 times (200%) motor current rating (maximum clockwise position)). To decrease the current limit, rotate the CL Trimpot counterclockwise.

Ideally, the CL adjustment should be carried out using a DC Ammeter if you have one, adjusting to around 1.5 times the current draw of the motor...( if your motor is the 550Watt version, that should be around 4.5 Amps....I'd set it so that it is mid way between the min and max settings of the preset, if someone has twiddled with it...and you dont have a suitable means of measurement

The ACCEL Trimpot Is normally set to 2 seconds, which is the amount of time it will take for the motor to accelerate from zero speed to full speed. To increase the acceleration time, rotate the ACCEL Trimpot clockwise. To decrease the acceleration time, rotate the ACCEL Trimpot counterclockwise.

The MAX Trimpot sets the maximum speed of the motor when the Main Speed Potentiometer is set fully clockwise. The MAX Trimpot is factory set to 100 % of base motor speed. To increase the maximum speed, rotate the MAX Trimpot clockwise. To decrease the maximum speed, rotate the MAX Trimpot counterclockwise. I normally adjust the Max speed by measuring at the motor leads, for 180V DC, corresponding to the speed of the motor and what it normally runs at.

 The MIN speed trimpot sets the minimum speed of the motor when the Main Speed Potentiometer is set fully counterclockwise. The MIN Trimpot is factory set to 0 % of base motor speed. To increase the minimum speed, rotate the MIN Trimpot clockwise. To decrease the minimum speed, rotate the MIN Trimpot counterclockwise.

 IR compensation is provided to substantially improve load regulation. If the load presented to the motor does not vary substantially, the IR adjustment may be set at a minimum level (approximately 1/4 of full setting). The control is factory adjusted to approximately 3% regulation.

Suffice to say, any adjustments should be carried out with an insulated tool......anywhere on these boards should be considered Live... :zap:

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