Speed Controller – Mini Lathe

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Speed Controller – Mini Lathe

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  • #370593
    Derek Leggott
    Participant
      @derekleggott56008

      Hi all, I wonder if anybody has any ideas on this problem. I've just bought and received a new mini lather: MosaicAL 600w 7×12 2500rpm with variable speed.

      Everything is absolutely fine apart from the issue i'm about to explain.

      I switched the lathe on and it worked perfectly. I adjusted the variable speed control to speed it up and then reduce speed and it was great for about 20 seconds. The there was a pop like a fuse blowing and the lathe went to full speed. No matter what i did with the speed control knob it stayed at full power.

      I have contacted the supplier but any ideas would be great.

      Many thanks

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      #26172
      Derek Leggott
      Participant
        @derekleggott56008
        #370690
        I.M. OUTAHERE
        Participant
          @i-m-outahere

          Sounds like the switching transistor has popped and gone short circuit . I have had IGBT 's do this but that was because i didn't pay attention to the gate voltage i was supplying it ! If it is new then claim warranty but get them to fit the new board or parts required to fix it then test it before you accept it back .

          #370694
          Derek Leggott
          Participant
            @derekleggott56008

            Thanks XD. I took the back of the lathe off to look at the board and there was an item that had blown. It could be a transistor. It has the words MIN below it and the one next to it has the words MAX below it. This one is sound. I also noticed that the earth strap that should have been connected to the lathe was just hanging loose!!

            I've got in touch with supplier to get it sorted anyway. Thanks again.

            #370695
            Neil Wyatt
            Moderator
              @neilwyatt

              Looks closer to a Warco WM180 than the lathes we normally call 'mini lathes'.

              Certainly sounds like a blown speed controller board, don't try fixing it yourself. The supplier shoudl be able to sort this out if all you have done is switch on and adjust the speed.

              Neil

              #370703
              JasonB
              Moderator
                @jasonb

                Looks more like that one somebody was asking about a week or two back and the general feeling was that it should only be switched on/off with a barge pole.

                #370730
                I.M. OUTAHERE
                Participant
                  @i-m-outahere

                  By the sounds of it the min / max being written below the components would to me indicate a potentiometer .

                  If you still have the back off would it be possible for you to post a few pictues of the board just for future reference if any one else needs it later on ?

                  I would definately be asking the seller to inspect the repair or replacement unit before you get it back ! Having the earth diconnected is extremely dangerous and could have killed you ! I would also be making them aware of that fact and also that it doesn't come up to the electrical standards of your country that they are required by law to adhere to !

                  I personally would want a refund then go and buy a machine from a more commonly know brand and seller – you will find them advertizing on this website on the right hand side of the page .

                  #370737
                  Derek Leggott
                  Participant
                    @derekleggott56008

                    img_0241.jpgHere are the photo's of the board.

                    img_0240.jpg

                    #370739
                    JasonB
                    Moderator
                      @jasonb

                      Are you sure that earth lead was not sandwiched between the main body of the lathe and the cover, probably in teh hole far left of first photo.

                      They are adjustment Potentiometers

                      #370743
                      Derek Leggott
                      Participant
                        @derekleggott56008

                        Hi Jason

                        There's a screw in the main body bottom left that it should be attached to via a nut. It hadn't been fixed and was just left floating around.

                        As a newbie to this is a Potentiometer the knob that adjusts the speed?

                        #370745
                        JasonB
                        Moderator
                          @jasonb

                          The knob on the front fixes to a large potentiometer "pot" to adjust the speed.

                          The four small blue components are also potentiometers but are adjusted with a screwdriver at the factory to give the desired running characteristics, they are not something that you should need to adjust.

                          #370747
                          Anonymous
                            Posted by Derek Leggott on 07/09/2018 08:55:35:

                            As a newbie to this is a Potentiometer the knob that adjusts the speed?

                            No, it's a preset pot. It will be used during manufacture to set a limit (minimum looking at the silkscreen) that the actual speed control pot will work between.

                            To blow the preset apart like that means something is seriously wrong. I suspect it's had mains, or the output voltage up it, which is worrying. One would hope that it's an assembly fault rather than a design flaw.

                            Don't even think about getting the board repaired; the supplier needs to replace the whole board.

                            Andrew

                            Edited By Andrew Johnston on 07/09/2018 09:11:29

                            #370751
                            Martin W
                            Participant
                              @martinw

                              A much more worrying aspect about this is that it appears that the NEUTRAL line is fused instead of the live line. If the fuse was to blow it would leave all the electronics at mains, 240VAC, potential which could prove lethal.

                              In this state the lathe will not comply with basic standards and certainly it will not comply with european/UK regulations. I would demand a full refund and get the seller to collect the lathe. If UK based then I would also raise this with the relevant trading standards authority.

                              Martin

                              #370754
                              Neil Wyatt
                              Moderator
                                @neilwyatt

                                I think you might find the 'unattached' earth lead was sandwiched between panel and housing using one of the fixing screws.

                                Not a very good idea as it could be insulated by the paint.

                                Let us know how you get on.

                                Neil

                                #370757
                                Michael Gilligan
                                Participant
                                  @michaelgilligan61133
                                  Posted by Neil Wyatt on 07/09/2018 09:51:21:

                                  I think you might find the 'unattached' earth lead was sandwiched between panel and housing using one of the fixing screws.

                                  Not a very good idea as it could be insulated by the paint.

                                  .

                                  To expand a little on "Not a very good idea" …

                                  Probably illegal to sell [but I don't have the patience to check]

                                  Certainly a nasty case of 'spoiling the ship' cost-cutting !

                                  MichaelG.

                                  .

                                  These may be of interest:

                                  https://www.electricalsafetyfirst.org.uk/mediafile/100129855/Buying-Electrical-Goods-Online-A5-Leaflet-2014.pdf

                                  https://www.gov.uk/guidance/electrical-equipment-manufacturers-and-their-responsibilities

                                  Edited By Michael Gilligan on 07/09/2018 10:15:12

                                  #370761
                                  Anonymous
                                    Posted by Martin W on 07/09/2018 09:45:54:

                                    In this state the lathe will not comply with basic standards and certainly it will not comply with european/UK regulations. I would demand a full refund and get the seller to collect the lathe. If UK based then I would also raise this with the relevant trading standards authority.

                                    That's a moot point in countries like Germany where the mains plug can be inserted either way round, so the equipment doesn't actually know which is LIVE and NEUTRAL.

                                    Andrew

                                    #370766
                                    SillyOldDuffer
                                    Moderator
                                      @sillyoldduffer

                                      Some serious power needed to blow a pot that spectacularly and only one component is effected, so the problem might be local to the pot. I wonder if the board is incorrectly stood off from the heat-sink – short pillars, or missing insulation underneath? I vaguely remember another example where a board blew when it touched the metalwork due to a simple installation error. It's the kind of assembly mistake where everything tests OK at the factory but…

                                      Martin's concern about the mains wiring needs checking out; the wire colours imply it's the wrong way round. The 'Live' pin on the plug should connect to the fuse, not the neutral. (This risk of having a fuse in the neutral line is that the equipment is still connected to mains power after the fuse blows, which might be a nasty surprise. )

                                      Hope this misadventure doesn't put you off Derek. Owning a lathe will be good fun once you've got past this hassle!

                                      Dave

                                      #370767
                                      JasonB
                                      Moderator
                                        @jasonb
                                        Posted by Neil Wyatt on 07/09/2018 09:51:21:

                                        I think you might find the 'unattached' earth lead was sandwiched between panel and housing using one of the fixing screws.

                                        Not a very good idea as it could be insulated by the paint.

                                        Let us know how you get on.

                                        Neil

                                        I was going by the fact the paint seems to be missing around that screw hole.

                                        #370769
                                        Michael Gilligan
                                        Participant
                                          @michaelgilligan61133

                                          From what I recall [*] good practice would require

                                          • the connection point to be a threaded post; either welded in place, or a screw tightly lock-nutted
                                          • an earth lead which is long enough to span the distance required to keep it connected, in the situation shown.

                                          img_2272.jpg

                                          As stated earlier, I'm unsure of the legalities.

                                          MichaelG.

                                          .

                                          [*] checking equipment when working at Kodak many years ago

                                          #370800
                                          Neil Wyatt
                                          Moderator
                                            @neilwyatt
                                            Posted by Michael Gilligan on 07/09/2018 11:17:04:

                                            From what I recall [*] good practice would require

                                            • the connection point to be a threaded post; either welded in place, or a screw tightly lock-nutted
                                            • an earth lead which is long enough to span the distance required to keep it connected, in the situation shown.

                                            img_2272.jpg

                                            As stated earlier, I'm unsure of the legalities.

                                            MichaelG.

                                            .

                                            [*] checking equipment when working at Kodak many years ago

                                            I doubt it's long enough to reach that point with the panel in place, I think it went with the one to its right – which seems to have intact paint…

                                            Neil

                                            #370802
                                            JasonB
                                            Moderator
                                              @jasonb

                                              "There's a screw in the main body bottom left that it should be attached to via a nut"

                                              Question was answered earlier

                                              #370808
                                              Michael Gilligan
                                              Participant
                                                @michaelgilligan61133
                                                Posted by JasonB on 07/09/2018 14:58:11:

                                                "There's a screw in the main body bottom left that it should be attached to via a nut"

                                                Question was answered earlier

                                                .

                                                Sorry, Jason blush

                                                As you had previously mentioned 'the hole at far left of the first photo' and there is pretty clear evidence of missing paint there, I assumed that the hole I indicated would be the one.

                                                MichaelG.

                                                .

                                                Edit: Now I'm not sure if you were correcting Neil or me.

                                                Edited By Michael Gilligan on 07/09/2018 15:25:28

                                                #370811
                                                Derek Leggott
                                                Participant
                                                  @derekleggott56008

                                                  Thanks for all your input everyone. It's been very helpful.

                                                  #370824
                                                  wheeltapper
                                                  Participant
                                                    @wheeltapper

                                                    I just found this model lathe on amazon.

                                                    there are two reviews, the second one starts' it had a faulty controller board that the supplier replaced'.

                                                    sounds like a few duff boards going round.

                                                    Roy.

                                                    #370842
                                                    duncan webster 1
                                                    Participant
                                                      @duncanwebster1
                                                      Posted by Martin W on 07/09/2018 09:45:54:

                                                      A much more worrying aspect about this is that it appears that the NEUTRAL line is fused instead of the live line. If the fuse was to blow it would leave all the electronics at mains, 240VAC, potential which could prove lethal.

                                                      In this state the lathe will not comply with basic standards and certainly it will not comply with european/UK regulations. I would demand a full refund and get the seller to collect the lathe. If UK based then I would also raise this with the relevant trading standards authority.

                                                      Martin

                                                      I've bought stuff form China where red was connected to neutral pin and black to live. A simple continuity checker would reveal all. I've also bought kit made in China but bought from UK which had a UK style plug but without a fuse. Trading Standards never got back to me so whether they followed it up I have no idea.

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