Announcement

Collapse
No announcement yet.

David Schwab's DeArmond repair

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • David Schwab's DeArmond repair

    David repaired this ancient beauty for me. It should be here any day...Click image for larger version

Name:	CRW_2326.jpg
Views:	1
Size:	2.69 MB
ID:	867053
    Can't wait!

  • #2
    David- Did it need to be rewound?

    Comment


    • #3
      Yes, I had to rewind it, and replace the cable to the control box. They are delicate and tedious to work on!

      I'll post some photos of it soon.
      It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. Albert Einstein


      http://coneyislandguitars.com
      www.soundcloud.com/davidravenmoon

      Comment


      • #4
        Originally posted by David Schwab View Post
        Yes, I had to rewind it, and replace the cable to the control box. They are delicate and tedious to work on!

        I'll post some photos of it soon.
        Must'a been tough going with that nasty (hand) injury you've had lately, good work.
        -Brad

        ClassicAmplification.com

        Comment


        • #5
          Originally posted by RedHouse View Post
          Must'a been tough going with that nasty (hand) injury you've had lately, good work.
          It was done before that, thankfully.
          It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. Albert Einstein


          http://coneyislandguitars.com
          www.soundcloud.com/davidravenmoon

          Comment


          • #6
            OK, here's some photos I took of the process.

            This is the pickup with the chrome bezel off:



            I had already unsoldered the cable and as you see I have a jewelers screwdriver inserted to pry the pickup from the baseplate. The bobbin material is extremely thin and brittle!



            You can see that some of the bobbin has chipped away. I used a number of different thin objects, including a couple of X-Acto knives and a .009" nut file, to slide under the pickup to free the contact cement. I had to move very slowly as to not crack the flatwork.

            And it's free!

            It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. Albert Einstein


            http://coneyislandguitars.com
            www.soundcloud.com/davidravenmoon

            Comment


            • #7
              Here's the bottom of the bobbin:



              Here's the top. I wasn't sure how the top cover plate was attached, but it was just a little contact cement.



              You can see the different size magnets. Also the magnet that would be under the B string is lower than the rest.



              Notice the bare hookup wire from the start lead. it was a solid wire. The finish wire was also solid and had cloth insulation, which was falling apart..
              Last edited by David Schwab; 01-16-2013, 08:12 PM.
              It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. Albert Einstein


              http://coneyislandguitars.com
              www.soundcloud.com/davidravenmoon

              Comment


              • #8
                Peeling off the very old masking tape:



                The pickup was wound with 44 AWG plain enamel.



                It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. Albert Einstein


                http://coneyislandguitars.com
                www.soundcloud.com/davidravenmoon

                Comment


                • #9
                  Please explain how it works?
                  Can't tell from the pics.
                  Where is the magnet?
                  Are they rod magnets in the P/U, or wound on a bar Mag, or what?
                  Thanks,


                  "If Wishes Were Horses, Beggars Would Ride!" Scottish Proverb 1600s
                  Terry

                  Comment


                  • #10
                    Here most of the tape is removed:



                    Because the coil was open, I weighed the bobbin to get an idea how much wire was on it. It weighed 22 grams.



                    Now all the wire is stripped from the coil.



                    Notice the separate core for the B/E strings. The two plain strings must have been a lot louder, so most of the coil is wound around the other four strings, and then less for the top two. I have had people tell me that the top two strings are weak when using modern gauges, so I decided to wind one coil, instead of the stock setup.
                    It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. Albert Einstein


                    http://coneyislandguitars.com
                    www.soundcloud.com/davidravenmoon

                    Comment


                    • #11
                      Another view. You can see the cracked part of the flatwork, from where i released it from the base:





                      The control box. This one had three caps! The third cap is under the large .02F cap. I drew out a diagram. I'll scan and post that later.

                      It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. Albert Einstein


                      http://coneyislandguitars.com
                      www.soundcloud.com/davidravenmoon

                      Comment


                      • #12
                        Because the bobbin was so fragile, and was separating from the magnets, I was concerned about it coming apart when I wound it. So the first thing I had to do was stabilize it. I did that with CA glue, and masking tape. I put some glue around the magnets, and pressed the tape down. This is the bottom.



                        Here's the second core is glued in. The core was clear plastic.



                        I continue with the glue and tape:

                        Last edited by David Schwab; 01-16-2013, 08:14 PM.
                        It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. Albert Einstein


                        http://coneyislandguitars.com
                        www.soundcloud.com/davidravenmoon

                        Comment


                        • #13
                          A few times I had to place the bobbin in a small drill press vice while the glue set. Once I had it feeling firm, I soldered the start of some 44 gauge poly to a hookup wire, and threaded it though the hole. I should have used a bare wire, but I removed the insulation later. I taped the start in, and wrapped a little taper around the core.



                          On to the winder. Because I was concerned with the bobbin coming apart as I wound, I used a small piece of perf board and a neo magnet to hold the top tight. If I had a tail stock winder I could have done it that way. But this worked fine.



                          Steve said he wanted it wound a little hotter. The problem was I had no idea how much wire was wound on the bobbin. So I wound it and looked to see when it was getting full. At this point I decided I didn't want to risk winding any more wire. The two ends were starting to flair up a little and lifted from the magnets.
                          I got 8,069 turns of wire on it. The finished bobbin weighed 28 grams, and read just under 10kΩ.

                          Last edited by David Schwab; 01-16-2013, 08:16 PM.
                          It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. Albert Einstein


                          http://coneyislandguitars.com
                          www.soundcloud.com/davidravenmoon

                          Comment


                          • #14
                            David, thank you so much for these exquisite photos, and meticulous recounting of the reconstruction. I feel like I was there at the bench!

                            The use of differential polepiece widths and the differential windings around the wound and unwound strings is absolutely fascinating and thought-provoking.

                            One of the thoughts it provokes is whether there is, in any sense an equivalency between polepiece width and magnet type. For example, could use of Alnico 5 for the low E and G, with Alnico 2 or 3 used for the A, D, B and E replicate what the different polepiece widths do in that context, or is the effect more one of timbre than sensitivity?

                            I guess a more general question is whether there are any pickups currently in production that use different polepiece widths.

                            In any event, thanks again. This is a real delight to look at.

                            Comment


                            • #15
                              I made my finish connection and taped up the bobbin. I had to apply some more glue and clamp the ends in the vice to push the flaring down a bit.

                              I wasn't going to wax pot it, but then I decided it would make it firmer, which is a good thing. So I put it in the wax for about 6 minutes.

                              Here it is back in the baseplate.


                              And all put back together! The original coax from the pickup to the control box had to be replaced. The center insulation was turning into dust, and it had shorted out to the braid.



                              These photos make it look like a quick repair, but it really took a while because I had to work very slowly, and also just plan out every step ahead of time. Then I would to dry runs to see the best course of action. Something simple like reattaching the dress plate on the front of the pickup was equally tricky!
                              Last edited by David Schwab; 01-16-2013, 08:19 PM.
                              It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. Albert Einstein


                              http://coneyislandguitars.com
                              www.soundcloud.com/davidravenmoon

                              Comment

                              Working...
                              X