Announcement

Collapse
No announcement yet.

Johnson Loredo T25-R Power Transformer

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

  • Johnson Loredo T25-R Power Transformer

    It has an open primary. Transformer has no markings. Three secondary windings: HV, Heaters, and another for SS circuits. No schematic to reference. Anyone have info on this?

  • #2
    Maybe ask them?

    http://www.johnsongtr.com/contact.html
    "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

    Comment


    • #3
      I'll give it a shot. Hopefully their customer service is better than their part selection.

      Comment


      • #4
        This looks almost identical to a Blues Jr. May go that route depending on how/if Johnson replies.

        Comment


        • #5
          This might help.

          T25-R_schematic.pdf
          "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

          Comment


          • #6
            Open primary? OK so you are at the what is there to lose stage. And no matter what, the old transformer has to come out. So remove the transformer, and take the end bells off and check the wiring. Transformers are wound with enameled wire, and then the insulated wires that go outside are soldered to the ends of those. Those solder joints can fail and the wires can break. You might get lucky and find a simply repaired condition. Also, MANY transformers have thermal fuses inside. Usually they are buried in the winding, but you can see the silvery wires from them contrasting with the copper wires of the windings.
            Education is what you're left with after you have forgotten what you have learned.

            Comment


            • #7
              Wait...Laredo?

              As in Tommy Webber?
              Education is what you're left with after you have forgotten what you have learned.

              Comment


              • #8
                Enzo, I thought about this and was heading that route but one of the screws has a nut that is stripped, go figure. I just didn’t feel like dealing with it this evening. Maybe tomorrow I will break out the bigger tools and manhandle it open. The Dude, thanks for the schematic. Also, I need to eat some crow here as Johnson has already gotten back with me. That was really fast.. in fact the fastest I have ever experienced through email. They said the chances of them having a power transformer are close to zero..well dang.

                Comment


                • #9
                  Can you upload a picture and maybe some dimensions?
                  "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

                  Comment


                  • #10
                    I had never heard of a Johnson tube amp. I have had some of the Reptone amps and really liked them, very underrated compared to other amps in the class. When I was gigging I would always through the 15 watt in as a backup to my tube amp.

                    Comment


                    • #11
                      Here are pics of the amp.
                      Click image for larger version

Name:	20190222_070352.jpg
Views:	1
Size:	3.01 MB
ID:	853148

                      Click image for larger version

Name:	20190222_070357.jpg
Views:	1
Size:	2.44 MB
ID:	853149

                      Click image for larger version

Name:	20190222_070401.jpg
Views:	1
Size:	2.78 MB
ID:	853150

                      Comment


                      • #12
                        Transformer:
                        Click image for larger version

Name:	20190222_070452.jpg
Views:	1
Size:	2.21 MB
ID:	853151

                        Click image for larger version

Name:	20190222_070504.jpg
Views:	1
Size:	2.31 MB
ID:	853152

                        Click image for larger version

Name:	20190222_070514.jpg
Views:	1
Size:	2.27 MB
ID:	853153

                        Click image for larger version

Name:	20190222_070539.jpg
Views:	1
Size:	2.20 MB
ID:	853154

                        Click image for larger version

Name:	20190222_070555.jpg
Views:	1
Size:	2.37 MB
ID:	853155

                        Comment


                        • #13
                          I have this transformer opened up. Looks like the thermal fuse is open. I'll get one of these on order and also replace these Chang filter CAPs. How do you all repair the cut transformer tape?
                          Last edited by tdlunsfo; 02-22-2019, 02:21 PM.

                          Comment


                          • #14
                            Originally posted by tdlunsfo View Post
                            I have this transformer opened up. Looks like the thermal fuse is open. I'll get one of these on order and also replace these Chang filter CAPs. How do you all repair the cut transformer tape?
                            "Paper" layers can be patched with adhesive Kapton tape/foil. The copper foil (if cut) needs to be thoroughly soldered across its width to produce a perfect short circuit winding. You may need an extra piece of copper foil for mending or completely replace it.
                            - Own Opinions Only -

                            Comment


                            • #15
                              Originally posted by Enzo View Post
                              Wait...Laredo?

                              As in Tommy Webber?
                              Young Laredo, my, how you've grown...
                              Last edited by eschertron; 02-22-2019, 07:52 PM. Reason: full movie quote
                              If it still won't get loud enough, it's probably broken. - Steve Conner
                              If the thing works, stop fixing it. - Enzo
                              We need more chaos in music, in art... I'm here to make it. - Justin Thomas
                              MANY things in human experience can be easily differentiated, yet *impossible* to express as a measurement. - Juan Fahey

                              Comment

                              Working...
                              X