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KBIC controller probs

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John Rudd:

--- Quote from: gazz on October 01, 2011, 03:36:47 PM --- i should get a short reading between the cathode and gate pins in both directions, but i should get a resistance flow thru anode to cathode, but not cathode to anode unless the gate has been triggered?
attatched the drawing of the pin layout from the data sheet,

--- End quote ---

The scr should behave as a diode when the gate is triggered.........A to K forward biassed

Gazz292:
gotya,
this second board seems pretty simple, just 2 transistors, one of them the scr... which is even marked as a diode on the board (D4) the other one a 5 volt reg,
theress 7 capacitors, 2 other diodes, 3 small resistors, the big brake resistor, 1 relay, an inductor, transformer and a bridge rectifier,

i'll take it out of circuit, and try to figure out what bit does what.

Gazz292:
i have me lathe working again,

bypassed the brake board, but kept power to it so the tacho still works, ment changing one wire, L1 was fed from the second board thru the relay, so it now has live to it from the nvr,

disconnected a load of wires, they all when through the direction change switch appart from 1, which went to I2 on the main board,

figured out it's that board that does the reverse speed slow down bit too, one of the stack of switches in the direction change switch operated only in reverse setting, and connected 2 pins together on the second board, which reduced the reverse speed available.

it also handled the 'return speed knob to zero before it'll turn on function'
but the main board ramps the power up slowly, and i read it can handle that, i'm used to turning the speed knob to off to stop the lathe anyway,

and i've put the reverser switch in forwards and taken the knob off, so i wont be tempted to change motor direction with the board powered up,

asked amadeal if they can supply the secondary boards, the controller board they list on the site is for the 7x12 lathes, mines the 7x14 (i always forget), which has a different power board and location of controls it seens,

Swarfing:
Sounds like the breaking resistor is at fault. If it is not doing it's job then it will trip? try swapping it out for a decent sand block of the same value.

John Swift:

Hi Gazz


if the interlock circuit is as I expect ,
a momentry loss of mains supply could cause the relay to drop out

I found not all the lucar push on connectors used on my lathe to made a good connection
(i'm sure one was only held in place by the rubber boot)

 the switch on the back of the potentiometer triggers the thyristor when the speed control is fully anti clock wise
the relay then switches power to the speed control board and the DC output (via the FWD/REV switch) to the motor
only when switched off the motor is connected to the breaking resistor

my guess at the circuit is below

John

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