Jun 132016

Update – The SEIG X2 miller eventually packed up – the motor control board had been playing up for years, and I usually left it powered up but just not running, as that way it would run when I wanted it to!  Anyway I figured the motor control board was busted.   The motor says its 240 Volt A.C.  so I got a cheap A.C. motor controller from ebay that blew all the trips  in the house when I turned it on.   I got a replacement but all it did was to cause the motor to buzz and emit a whiff of smoke if I turned it up a bit.  I got out an old laboratory Variac – a rotary variable transformer giving from 0 to 260 volts A.C. and connected that but all I got was the buzzing – I didn’t dare turn it up very far.  The motor only had 2 wires going to it, so couldn’t be anything fancy, i.e. not 3 phase or feedback controlled or whatever, so the only thing left to try was D.C.   I got a 3 Amp bridge rectifier (ebay again) and wired it between the Variac output and the motor, with a switch and a fuse in the old control box on the front of the machine.  Success! it runs nicely from about 40 Volts and has much more torque at low speed than the original controller and is altogether much better – I haven’t tried it above about 140 volts as I haven’t needed to, but it runs very well – I’m not sure that I’d use the Variac’s ability to feed voltages above the mains voltage, and I’ll be careful when turning it to higher voltages for the first time.   If you have an old SEIG X2 with a motor that says 240V A.C. and has two wires (plus a yellow/green earth) going to the motor and you have trouble with the control board, look on ebay for an old  Variac, or Variable transformer capable of 2 or 3 Amps or more, and connect it up via a 3 amp 400Volt bridge rectifier.  I took the potentiometer out of the original control box and drilled out the hole and replaced it with a two pole single throw switch using ‘faston’ blade terminals…. Wish I’d done it years ago!  The Variac  will be too big to mount on the machine so it will have to sit on the bench or a shelf – but that is a small price to pay for getting the machine working again, and you can’t buy anything much better for the price…

I’m still left wondering what the original control board did with all its complicated circuitry?

old post……

I have a small  Axminster  SEIG X2 milling machine ( the same miller is widely sold under different brands) that is 5 or more years old.   It is a bit wobbly and weak for cutting steel, but I can usually manage by taking small cuts, although it does chip tools occasionally when the work jumps into the tool particularly if I forget and cut in the wrong direction.  For a long time it has had an annoying problem with the motor drive circuit – the speed control potentiometer has a switch to turn the power on, but you have to wait some variable time between switching the pot on and advancing it to run position or it doesn’t run at all.  The delay is a bit variable, between a few seconds and a couple of minutes when its first turned on.  I gather from the internet that this is a known problem.   I’m going to have a go at finding the problem – a timing issue of seconds to minutes that gets shorter as the circuits warm up suggest electrolytic or tantalum capacitors as the source of the problem, but I’ve failed so far to find a circuit diagram of the circuit on the board.   Axminster will sell me a board for £101 but don’t have facilities to repair boards, so I am challenged to find a solution… watch this space as I flounder around……

I took my testmeter into the shed and had a look at voltages – the speed control pot has -5.7 Volts across it, and when it starts properly the voltage stays at -5.7 at all speeds.  If its not starting as you turn the pot, the voltage drops to about -4 V at ‘full speed’ position.  The back of the board is a mass of surface mount stuff, so I’m not sure I can work out the control circuitry – there are a couple of multipin I/Cs that don’t have numbers on them, but I’m pretty sure the problem is in the very first stages of the speed control  – I just need some way of pinning it down a bit….


Well, I didn’t find anything wrong, but whatever I did or didn’t do, it is now much better and starts almost instanly 90% of the time – I begin to believe some of the comments on the web concerning bad joints….  A mystery, but since its functioning I will use it and worry when it goes wrong again….



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