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KBIC controller probs

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picclock:
Just a thought, it may be the speed control pot itself. Wiggling it or tapping it when the fault occurs may indicate this. Easiest way to test if intermittent is to replace.

Best Regards

picclock

Gazz292:
speed pot, something i havent tested, the switch part of it works fine, as the relay clicks on when the knob is turned to on, and off when it's turned to off,
tapping the pot knob does nothing, but if the track is bad at the very begining, the board may be locking out as it thinks it's trying to be started up at a position other than low speed,

the guard interlock works the NVR switch, basicaly power is routed from the nvr thru the guard interlock then to the board's input.

Gazz292:
not the speed pot, that measures out fine,

i did notice one of the transistors on the second board gives a strange reading, between middle and one leg short, both ways, no circuit between middle and other leg... both ways, that's not good me thinks, and that particular trannie is the one that one of the wires from the main board goes through to get to the rest of the circuit,

looking up the numbers now to see where i can get one, i bet maplins wont have em, heck, do they even sell electronic components anymore, just thing how many more kiddies toys they can fin in the shops if they get rid of the electronics stuff.

i did try something... the second board has wire marked I2, which i assume is inhibit, it goes to I2 on the main board, with that wire disconnected it's still the same, so i'm guessing the second board is inhibiting the main board,

oh yeah, just in case anyone knows their transistors.... the one in question is 'MCR 100-6 P86'  there is one other transistor on that board, and that is 'CJ 78L05 011'
if i can find replacments for those 2, i'll bung them in and see what happens,

John Swift:
78L05 is a 100mA 5v regulator in a TO92 case    http://www.alldatasheet.com/datasheet-pdf/pdf/6798/NEC/78L05.html

   John

ps        mcr 100-6 is a thyristor   http://www.alldatasheet.com/datasheet-pdf/pdf/4632/MOTOROLA/MCR100-6.html

andyf:
Does the Current Limit LED fitted on the KB board (near the "A-" connector) light up when the problem arises? If so, it might be worth noting the setting of the CL trimpot and then giving at a twiddle or two before returning it to the original setting.

I suppose one way of establishing if the KB board is the problem would be to bypass everything but that board and the motor. This could be done with a mains plug (with a 3A fuse in it for safety) in a switched wall socket, and a flex taking the live and neutral direct to L1 and L2 on the KB board, with the earth going to wherever the existing earth terminal is on the lathe. Leave the speed pot connected to P1, P2 and P3. Then, connect A+ and A- on the board direct to the motor. If there are connections to I1 and I2, disconnect them.

In effect, your KB240 is now connected up just like the one I have fitted to my old milling machine, except that I put an NVR switch on that.

With the speed pot turned down to slow (but not clicked off), turn on the power at the wall switch and then wind up the speed pot to see if the motor runs normally. If the spindle turns in reverse (there is now no Fwd/Rev switch in circuit) then it will probably only run at half speed, just as it did when all was well. Transposing the connections to A+ and A- will get it running forward and at full speed.

If the problem disappears, then the KB board is OK.

Remember that mains voltages are involved, so be careful. If you feel at all nervous don't try this test.

Andy

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