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B-15N Power transformer replacement

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  • B-15N Power transformer replacement

    Hello, I've acquired a replacement PT for my B-15N but the wire colors don't match the existing PT.
    The replacement acquired on ebay from DBHarmony has no paperwork or brand name just a series of numbers 300708-1 89300030 and E.I.A. 682 0434. Can anyone help to identify this PT so maybe I can track down its manufacturer for a diagram? Or any suggestions how to procede? --Billy

  • #2
    Does the seller have no documentation to share? Will the seller tell you where the thing came from? Did the seller claim it was a replacement for your model amp, or just for amps in general?

    What wire colors do you have now? Use an ohm meter to determine which wires are related. Windings with heavy wires and measureing less than an ohm should be heater windings.
    Education is what you're left with after you have forgotten what you have learned.

    Comment


    • #3
      Manufacturer is electrical windings, now called TMI
      Transformer EIA codes
      Originally posted by Enzo
      I have a sign in my shop that says, "Never think up reasons not to check something."


      Comment


      • #4
        The seller says he has no documentation, and claims it is a replacement. For those who know about B-15N's the power transformer doesnt fit other models (as far as I have heard).
        The power transformer is E.I.A. #682 which I did find out is made my TMI (formerly Electrical Windings).

        The old Transformer's colors are pretty simple: 2 yellows to a 5AR4 Tube, 2 Reds to another 5AR4 tube, 2 Greens to a 6L6GC tube, Red w/yellow stripe to standby switch, a black to a grounding switch, and a black to the 3 amp fuse.
        The new transformer also has 9 wires: 2 reds, yellow, yellow w/red stripe, white w/green stripe, white w/yellow stripe, white w/black stripe, Green, and black
        I've done minor electronics and can solder but can you explain further how to test the resistance and explane the what the heater windings are. Thanks for alll the help. --Billy

        Originally posted by Enzo View Post
        Does the seller have no documentation to share? Will the seller tell you where the thing came from? Did the seller claim it was a replacement for your model amp, or just for amps in general?

        What wire colors do you have now? Use an ohm meter to determine which wires are related. Windings with heavy wires and measureing less than an ohm should be heater windings.

        Comment


        • #5
          Heaters (also called filaments) are the glowing things inside every tube.

          Your old transformer had the standard wire colors:
          yellow - 5vAC for the rectifier tube heaters
          green - 6.3vAC for the other tube heaters
          red - high voltage - several hundred volts AC
          red w/ yellow stripe - center tap of high voltage winding (often written as r/y)
          black - primary (your 120v mains from the wall outlet)

          Like its schematic symbol suggests, each of these wire groups are a winding of wire inside the core of the transformer. SO if you just had all those wirs sticking up in the air, you would find with your ohm meter that some are connected to others. Specifically the two greens are connected together, the two yellows are connected together, the two reds together with the r/y also, and the two blacks together. And you will also find that none of the groups are connected to any of the others. None of the reds are connected to the greens or the yellows, the blacks to none of the others etc. If any of those rules are violated, the transformer is probably bad.

          Not everyone uses the old color code these days, especially in other countries, but even in the USA, we find for example the 6.3v wires on most Peavey amps are yellow rather than green. SO your new transformer is one of these. SO in the absence of data, I'd get out my ohm meter, and pick a wire. Clip one meter probe to the wire. Now touch the other probe to each of the remaining wires, one by one. Note which other wires it shows a connection to on a paper. Mark that wire somehow - tape, bend it, knot it, whatever. pick the next wire and see what it connects to. Go through all of them, you listed 9, and see which ones connect to which others. And take note of the resistance.

          Heater wires will be heavier wire usually, but they will have a very low resistance, probably less than an ohm. But the high voltage might read 200 ohms or more.
          Education is what you're left with after you have forgotten what you have learned.

          Comment


          • #6
            Originally posted by Billyaxe View Post
            The seller says he has no documentation…
            That’s a really lame transformer company or more likely a really unhelpful employee who answered your question.

            Originally posted by Billyaxe View Post
            The old Transformer's colors are pretty simple: 2 yellows to a 5AR4 Tube, 2 Reds to another 5AR4 tube, 2 Greens to a 6L6GC tube, Red w/yellow stripe to standby switch, a black to a grounding switch, and a black to the 3 amp fuse.
            The new transformer also has 9 wires: 2 reds, yellow, yellow w/red stripe, white w/green stripe, white w/yellow stripe, white w/black stripe, Green, and black…Billy
            My take is this:
            1. The two reds on the new transformer = the two reds on the old
            2. The new wire you list as “yellow w/red stripe” is probably meant to be red with a yellow strip and equals your old red with a yellow strip.
            3. The new green and new “white w/green stripe” are the 6.3 volt heater winding and equal to your old two greens.
            4. The new yellow and new “white w/yellow stripe” are the 5 volt heater winding and equal to your old two yellows.
            5. The new black and new “white w/black stripe” are the primary winding and equal to your old two blacks.


            Edit: And I see that I was typing while Enzo was answering and he has explained how to Ohm out your windings.
            Last edited by Tom Phillips; 04-20-2013, 01:22 AM. Reason: additional comment

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            • #7
              Make these measuremnets with the power OFF, please.
              Enzo did note "resistance maesurements'.
              Pedantic am I.

              Comment


              • #8
                Yes, no power during resistance readings.

                My mental image was of the new transformer not yet wired, since he had no idea which wire was which. But I should not assume...
                Education is what you're left with after you have forgotten what you have learned.

                Comment


                • #9
                  B-15N Power transformer wiring

                  Thanks guys and Enzo for putting things in simple terms so I can learn along the way. The transformer I am testing is the new one not hooked up. The old one is still in the amp.
                  I did testing with a continuity tester and also with an impedence tester. Here's the ones that matched impedence wise:
                  16awg Green with 16awg White/G at .7 ohms
                  16awg White/Y with 22awg Yellow at .3 ohms

                  I didnt read 200 or so ohms on anything as you expected, so dont know what would be the high voltage wires. I would guess the reds, but is there anyway I can be closer to sure?

                  I got continuity on the following, but 0 resistance:
                  22awg Black with White/B
                  all 22awg Red with Red with Yellow w/R

                  So Enzo, with this info can I assume you are right that I can use the greens, yellows (even though one is 22 guage), and reds in place of those respective colors on the old PT?
                  If so, my next questions will be:
                  I need a wire each to a Standby switch, a grounding flip switch, and a 3amp fuse.
                  I'm not sure how the Yellow w/R relates as a third wire to the red?

                  Many thanks for the help on this. --Billy

                  Comment


                  • #10
                    Yellow/red goes where red/yellow was, standby switch.
                    Black to fuse
                    White/b to ground switch.
                    Originally posted by Enzo
                    I have a sign in my shop that says, "Never think up reasons not to check something."


                    Comment


                    • #11
                      B-15N Power transformer wiring

                      Originally posted by g-one View Post
                      Yellow/red goes where red/yellow was, standby switch.
                      Black to fuse
                      White/b to ground switch.
                      Okay thanks. It looks like I have everything I need to wire up the replacement. Any second opinions out there? Enzo, you ironed out the first 6 wires for me, does the last three agree with you? Thanks to all for the help. --Billy

                      Comment


                      • #12
                        I deal with it conceptually. If you have found the primary wires, apply mains voltage to it and see if the wires make the desired voltages. I trust my fellow posters in this thread.
                        Education is what you're left with after you have forgotten what you have learned.

                        Comment


                        • #13
                          Originally posted by Enzo View Post
                          .. .If you have found the primary wires, apply mains voltage to it and see if the wires make the desired voltages...
                          That’s the verification test you need to do to determine if the transformer is correct for your amp. Especially to clear up the following:

                          Originally posted by Billyaxe View Post
                          16awg Green with 16awg White/G at .7 ohms
                          16awg White/Y with 22awg Yellow at .3 ohms
                          …I got continuity on the following, but 0 resistance:
                          22awg Black with White/B
                          all 22awg Red with Red with Yellow w/R
                          Because it doesn’t make sense that you got the .7 and .3 Ohm readings on the low voltage windings but then got “0 resistance” on the high voltage winding.

                          Comment


                          • #14
                            Originally posted by Tom Phillips View Post
                            Because it doesn’t make sense that you got the .7 and .3 Ohm readings on the low voltage windings but then got “0 resistance” on the high voltage winding.
                            Yes, that's one of Enzo's pet peeves, “0 resistance” meaning zero ohms or no reading open circuit or out of range.

                            Comment


                            • #15
                              B-15N Power transformer wiring

                              Originally posted by Enzo View Post
                              I deal with it conceptually. If you have found the primary wires, apply mains voltage to it and see if the wires make the desired voltages. I trust my fellow posters in this thread.
                              Oh I thought I was very close to solving this, hopefully it's still within my ability based on your instructions. Sorry I have to ask for simple terms.
                              So when you say 'primary' that would be where 110 volts would be applied, right? Did I indicate to you, by what I described, that I found the primary wires?
                              If I know what those wires are, am I applying a hot and neutral and does it matter which is which? Then these 'desired voltages' would be read on the heater wires? And how do I know what voltages they are?
                              Thanks --Billy

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