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Help needed diagnosing problem with variable speed router motor.

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  • Help needed diagnosing problem with variable speed router motor.

    I have an Elu MOF177e router, probably 30 years old. Not been heavily used or abused and generally well cared for. I needed to use it yesterday after a period of say a year of no use. On switching on the motor will turn ok but there is a lot of flashing from the brushes. There is possibly a slight pulsing nature or stuttering as it turns. The variable speed works in that it will slow and speed the motor ok.

    I stripped the top of the router, blew out what little wood dust was in there and pulled and checked the brushes which were ok except for a little pitting on one edge which I assumed was from the flashing.

    Checking on line I was surprised to find that I can still get spare parts for this machine. It still exists as a DeWalt model. The problem is figuring out what I need to replace. As I see it the items that could be faulty and can be replaced are 1. the brushes 2. a capacitor which is wired across live and neutral (?suppressor?) and 3. the electronic speed controller.

    The replacement brushes are cheap as is the capacitor but the speed controller is £100.

    My query is whether there are clues in the symptoms about what may be faulty or should I replace the cheap parts first then if it doesn't work replace the speed controller.

    I don't really know a lot about motor speed control and could do with another set of eyes to run over my logic.

    Thanks guys


  • #2
    ELU made great tools. I have a combo table saw/compound mitre saw. Black & Decer bought the right for ELU & then made the B&D tools yellow & named them DeWalt. If you can't get the speed control working but it works good on high or 1 speed buy a variable speed router control from someone like Harbor Freight where the power tool plugs into it & it plugs into the wall with a knob on the unit to control the speed. $19.95- $5 with a 25% coupon=$14.95.
    Last edited by flylo; 01-14-2018, 05:41 AM.
    "Let me recommend the best medicine in the
    world: a long journey, at a mild season, through a pleasant
    country, in easy stages."
    ~ James Madison


    • #3
      The problem with my one that had those symptom's was the bearings slowing it down.
      Once I replaced the bearings it has been fine since, you could try some penetrating oil and see if it speeds up.

      I have tools I don't know how to use!!


      • #4
        Could also be a dirty commutator. The segments should be bright and shinny not dull and brown that comes with age.


        • #5
          I have an old one mof somthing, pre b& d, as pointed out the bearings probably need a clean and lube, plus commutator, clean the copper, and the brusholders, do all the cheap stuff, at least that will get eliminated before paying for a new cercuit board,
          I bought a second (more like 4th) hand 1/2 " to rout out stair housings, it was/is an animal of a thing, I couldent slow it, due to the taper on the housing cutter of 95 degree you have to go full depth, I should have taken the bulk with a straight bit but as you do, not thinking just carried on, it ate it, so much chips I had to get a dust collector hose on the router to even see, not that I needed to in a jig.
          Whichever it's worth repairing even at 100, couple of carpenters have offered to buy mine at list price for a festool!, I thought they were joking, but no.
          Aparently they command a high price in good condition (I think they were more keen as they had all the elu table, accessories etc myself)


          • #6
            I had the exact same symptoms on my Bosch router. Im afraid it's very likely to be a fault in the armature.

            I wanted to repair it as I had accumulated a lot of extras for it - guide bushes and a few special purpose jigs etc., but the price of a replacement armature was extraordinary - something over £180. I solved the problem by buying a complete, working but rough second hand router on eBay for about a third of that amount and swapped out the armature.

            That one's now a good source of otherwise expensive spares, but I also machined down the old armature to make a collet extender which would have cost almost as much new as I paid for the router...!




            • #7
              Do the sparks carry around in a circle around the commutator? That can indicate an open commutator segment.

              Keep eye on ball.
              Hashim Khan


              • #8
                Thanks for all the ideas.

                I think I'll start with the simple stuff first, clean up the commutator and look at the bearings etc.

                Sparks do not go round in a circle, I know what you mean Jerry but it's not like that plus there is a stuttering sound.

                Mark, I know these things are worth fixing, compared to modern routers they are incredibly well made and robust and very powerful.
                As you say ideal for routing out stair stringers and housings.

                Will keep you all posted with progress.



                • #9
                  I loved Elu.. Still have the belt sander and planer from the same period. For those that don't know, Elu tools were made in Switzerland, then Elu was bought by B&D Professional then merged with Dewalt.

                  If it's a conventional series wound motor (likely from the day) simply using a 2 wire"in line" connection to the motor, you can bypass the speed control to test that. Inspect the armature throughout. Look for an open segment (look and probe carefully at the wires right where they come to the commutator - crimps get loose; then for shorts or burnt wiring. A shorted or burnt segment will often look a different (darker) color than the other windings. The commutator surface should be smooth and the individual segment insulators slightly undercut.

                  I just "inherited" a new'ish dying 12 inch slide compound miter DeWalt saw. Hey, if you can fix it you can have it". Huh, like you want it back if I can't?.

                  Ran slow, noisy, sparked a lot, and overheated. Armature "looked" good, but the field was burnt. Crap. Close look at the armature showed one coil discolored and charred at one end. $190 in parts... Would have only needed one part if the idiot that ran it stopped when it started running bad.
                  Last edited by lakeside53; 01-14-2018, 12:07 PM.


                  • #10
                    Also what can happen with a motor of that age, the commutator could need turning and/or undercutting.
                    The material often used between the com bars was mica, which if not undercut at sometime during the motor life, can cause excessive brush wear and sparking, now more modern materials are used that generally wear at the same time as the copper.
                    On these generally, there is no need for undercutting.


                    • #11
                      Here's a list which may be outdated as I know Skil or Stanley bought part or the US rights to husqvarna a few years back. In most cases except maybe Dewalt the quality suffered while chinese brand quality is getting better just as I saw japan do in my years.
                      "Let me recommend the best medicine in the
                      world: a long journey, at a mild season, through a pleasant
                      country, in easy stages."
                      ~ James Madison