Author Topic: Mini Mill Woes  (Read 5339 times)

Offline RayW

  • Full Member
  • ****
  • Posts: 735
Re: Mini Mill Woes
« Reply #15 on: April 17, 2020, 03:32:32 PM »
Thanks all for your replies and suggestions. I must admit that I am completely out of my depth where electronics are concerned.

Andrew and Admiral-dk - I am happy that the little orange component has not melted as I initially thought. I think Admiral is correct and that the middle one has been sealed to avoid adjustment as there is clear printing on all three components.

Don - Can you explain more how to test the speed pot please. I have checked the voltage by connecting my voltmeter to the live input on the on/off switch and the negative to the input side of the pot and I get a reading of 240 volts. With the pot in the off position, if I connect the negative to the output side I also get 240v. If I then switch the pot on, the voltage on the output side drops to 74 regardless of the position of the pot.

Jason - I have heard that trick too, but as there is zero reading at the connections for the motor, that wouldn't work.

Zephyrin - Do you have any photos of the modification to your X2 please?

Mike - That looks good but the wiring up might be beyond me

Ray

Offline Don1966

  • Full Member
  • *****
  • Posts: 6817
  • Columbia, MS
Re: Mini Mill Woes
« Reply #16 on: April 17, 2020, 05:50:53 PM »
Ray you have a red, yellow and white wire on the pot. This is your reference voltage put you meter on the red and yellow wires the two outer wires it should have 5 or 10vdc on it depending on the manufacture. Make sure to turn the unit on with the pot switch.... if you have the voltage check again the voltage on the white and yellow when varying the pot. The voltage should vary as you turn the pot. Like Jason suggested a lamp across the motor output terminals can help to see if your producing an output. Just make sure the lamp is 240 v rating.

Don

Offline Barneydog

  • Full Member
  • ****
  • Posts: 211
  • Just outside Leicester, United KIngdom
Re: Mini Mill Woes
« Reply #17 on: April 17, 2020, 07:05:47 PM »
Hi Ray,
Since you have ordered one fit tge new speed control but I doubt it is that.
The pots are factory set for max and min speeds, torque cut out etc. My board packed up some years ago as tgey are VERY prone to do. I swapped mine for a simple dc speed controler off ebay for about a tenner and works fine just has no torquw cut out but who really needs it....just listen to the motor. The boards are the same rubbish as tge lathes. My C3 lathe has a torque problem ie it cuts out too early. For example it kept cutting out today drilling stainless 303 with a 3.2mm drillbit. I will either swap for cheap dc controler or try to adjust the torque pot. Problem is finding which to adjust. I think little machine have all the board specs on their site.
Not worth buying board just use cheap 200v bc controler from ebay.

Jules

Offline RayW

  • Full Member
  • ****
  • Posts: 735
Re: Mini Mill Woes
« Reply #18 on: April 17, 2020, 08:07:48 PM »
Thanks Don and Jules. Tried taking a reading across the terminals you suggested Don, but got zero reading. Do I assume that this means the pot is faulty? I will solder the new one in when it arrives and see if that cures the problem. If not, I am tempted to go with your suggestion Jules and fit a simple speed controller. If possible I would like to find one with forward and reverse although the times when i have wanted to run the mill in reverse have been very few and far between. As for torque cut out, my mill has been converted to belt drive so the belt will usually just slip if the cutter is overloaded.


Ray

Offline jadge

  • Full Member
  • ****
  • Posts: 503
  • Cambridge, UK
Re: Mini Mill Woes
« Reply #19 on: April 17, 2020, 08:34:08 PM »
To state  the obvious if you use a bulb as a load it needs to be an incandescent bulb. Is the motor brushed DC? In which case the output of the board will be a PWM signal rather than a DC voltage.

Andrew

Offline Jasonb

  • Full Member
  • *****
  • Posts: 9464
  • Surrey, UK
Re: Mini Mill Woes
« Reply #20 on: April 17, 2020, 08:38:47 PM »
yes they ar ebrushed DC.

I think that is why the light bulb is suggested as a basic tester won't show anything due to the PWM

Offline jadge

  • Full Member
  • ****
  • Posts: 503
  • Cambridge, UK
Re: Mini Mill Woes
« Reply #21 on: April 17, 2020, 09:03:40 PM »
Assuming that the PWM frequency is high then a digital meter will act as an integrator and will give a reading, albeit not necessarily accurate. An old school analogue meter would be better. The advantage of bulb is that it puts a reasonable load on the output as well as glowing more or less brightly.

Andrew

Offline RayW

  • Full Member
  • ****
  • Posts: 735
Re: Mini Mill Woes
« Reply #22 on: April 17, 2020, 09:29:12 PM »
I tried a bulb across the terminals where the motor connects, but nothing.
Ray

Offline Don1966

  • Full Member
  • *****
  • Posts: 6817
  • Columbia, MS
Re: Mini Mill Woes
« Reply #23 on: April 17, 2020, 09:35:20 PM »
Ray if you don’t get an output across the pot the unit won’t work no matter if you change the pot. It is defected and needs replacing. Without the reference from the pot nothing will work.


Don

Offline jadge

  • Full Member
  • ****
  • Posts: 503
  • Cambridge, UK
Re: Mini Mill Woes
« Reply #24 on: April 17, 2020, 09:52:07 PM »
It is defected and needs replacing.

Agreed. The regular failure of these types of board just go to confirm the saying that any idiot can design a power circuit that will work. But it takes expertise, and costs money, to create a design that works reliably and will survive the external faults that can occur.

Andrew

Offline Allen Smithee

  • Full Member
  • ****
  • Posts: 1130
  • Mordor, Middle Earth
Re: Mini Mill Woes
« Reply #25 on: April 17, 2020, 10:01:14 PM »
I think that is why the light bulb is suggested as a basic tester won't show anything due to the PWM

It certainly should - incandescent lightbulbs will work with AC, DC, Chopped DC or indeed anything that develops an RMS voltage. They just heat up due to the current passing through a resistance, and they don't care which way that current is flowing. Dimmer switches are like PWM - they chop the current into short bursts - the only difference is that they chop AC rather than DC, so we consider them to have chopping angles rather than chopping periods.

PDR
Quidquid latine dictum sit altum sonatur

Offline jadge

  • Full Member
  • ****
  • Posts: 503
  • Cambridge, UK
Re: Mini Mill Woes
« Reply #26 on: April 17, 2020, 10:36:51 PM »
Missing comma causes confusion!

Andrew

Offline Barneydog

  • Full Member
  • ****
  • Posts: 211
  • Just outside Leicester, United KIngdom
Re: Mini Mill Woes
« Reply #27 on: April 17, 2020, 10:51:46 PM »
Ray,
Dont spend too much more money just buy cheap controler from ebay. I have had no use for reverse so just got forward variable. Make sure you buy one with higher wattage than you need...500?

JULES

Offline awake

  • Full Member
  • ****
  • Posts: 303
Re: Mini Mill Woes
« Reply #28 on: April 17, 2020, 11:40:54 PM »
I would venture to guess that on any controller, forward and reverse are controlled simply by swapping the positive and negative poles of the DC output. All you need is a DPDT switch rated for the voltage & current.
Andy

Offline RayW

  • Full Member
  • ****
  • Posts: 735
Re: Mini Mill Woes
« Reply #29 on: April 27, 2020, 11:49:32 AM »
Thanks for all the advice  guys. I have now ordered a Chinese speed controller box and awaiting its arrival. I did receive a new speed controller pot from Arceurotrade so will wire that in to the old board just to see if that was the problem.
I also eventually got a quote from Clarkes for a replacement controller board - £170!!
Considering I have already paid out £115 unnecessarily for a new motor and that I only paid about £250 when I bought the mill secondhand, I think less than £20 for the Chinese unit is a no brainer.
Ray

 

SimplePortal 2.3.5 © 2008-2012, SimplePortal