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⭐️ Yamaha ERG121 ⭐️very low volume problem, Help! ⭐️

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  • ⭐️ Yamaha ERG121 ⭐️very low volume problem, Help! ⭐️

    Hi I'd really appreciate some help with getting my Yamaha ERG121 playing right.

    Bought s/h and hasn't been used in a while.

    Problem is the volume stays really low so the amp needs to go right up causing loads of buzzing.

    The condition in general is excellent, I've looked at the internal wiring and it all looks solid and matches the wiring diagram linked below, from what I can see.

    The plug input was a bit corroded so cleaned that all up fine.
    The 5 way switch seems to work
    Volume works
    Tone works

    I just don't know how to narrow down what the problem is.

    Can someone give me help or advice, or point me to some help please

    This appears to be the wiring for the model and it appears unaltered-

  • #2
    Get a Digital Multimeter and set to ohms (resistance) range. Turn the tone to brightest, volume to max and plug a lead in. Measure the resistance between the tip and sleeve of the other end of the lead using the meter. Check in all switch postions. You should get under 10K ohms in all positions. If higher than this then open 'er up and we'll need to do some testing inside. Also, turn the tone fully the other way and check you get the same readings.
    Experience is something you get, just after you really needed it.


    • #3
      Oh thanks for taking this on nick

      Right so I've tried to do what you said ....

      Set the multi meter at the 2000k on the Ohms (this seems to work best and I think I saw it on a youtube vid, not one that actually help!)

      Volume and Tone at Max
      1/Neck Hum - 245K
      2/mixed - 245K
      3/Single- 245K
      4/mixed- 245K
      5/Bridge Hum- 245K

      Volume Max, Tone Min
      All same results

      Note: lowering the volume does lower the resistance to zero

      It is already opened up just to check if the wiring looks the same as the diagram, which it seems to. Also the wiring and soldering looks good. Better keep it open

      I like the way your instructions sound like you know exactly what your looking for, because I really don't haha


      • #4
        Well, you do have an open connection somewhere, probably the switch is bad or the white wire from the switch to the tone control is broken or has a bad solder joint. Let test some more to narrow it down.

        So, inside and again on the ohms range put one probe on the metal body of the volume and the other probe on the following points report the ohms on all 5 places:

        Click image for larger version

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        Experience is something you get, just after you really needed it.


        • #5
          I agree with nickb that theres probably a bad connection somewhere. Since you mentioned the switch seems to function properly I would start my testing in the areas at and after the switch output. Points 1 and 2 on his drawing above, and also the output from the volume to the jack and the jack connection. I'd touch these up with solder and see what happens. I'd also do the ground connections, esp. the back of the volume pot. I'd probably go there first actually.


          • #6
            Please do the tests suggested by Nick on post #4 first, and report results.
            Then based on what was measured we can suggest other hypothesis.
            Suggesting possible "solutions" without first getting answers to simple and precise instructions which do have a definite purpose will only confuse the OP.
            Sorry for being a procedure Nazi but we are dealing with somebody at the far far away end of a Net connection doing the testing for us and we need results to proceed.
            Juan Manuel Fahey


            • #7
              Thanks for all the suggestions. I've taken some pics.

              I noticed that the 5 way switch is flipped 180 in the guitar so hopefully the pics will confirm I'm doing the checks right.

              Main elecs
              Click image for larger version

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              Jack plug
              Click image for larger version

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              Tone pot
              Click image for larger version

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              Switch/Vol pot (annotated how I tested)
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              Test results

              Ok so resistance between volume pot back and 1 - 5 (based on diagram and my interpretation of how it's installed)

              1 - 245K
              2 - 245K
              3 - 11K
              4 - 7K
              5 - 11K

              The jack plug looks ok to me as do the connections but hopefully the pics will help get another opinion or the results will just make sense.
              They seem to be showing a pattern for 3 to 5 for HSH pickups, beyond that I'm a bit lost haha!!
              Last edited by Stewbee; 03-05-2018, 02:20 PM.


              • #8
                Nicely done The switch is bad.
                Experience is something you get, just after you really needed it.


                • #9
                  Cheers awesome

                  So you can tell that it's just the switch that's gone!!

                  As if to confirm, I've just fiddled the switch back and forth a million times ...ish, and you can get sound from the centre single coil, just.

                  Ok so can I ask for some advice on a replacement. It's a standard 4cm/strat spaced one from my measurements.

                  This one seems ok:

                  Any thoughts?


                  • #10
                    Looks good. I have a 3 way version of one of those. It feels better than the original due to the very positive detent feel, yet smoother too.
                    Experience is something you get, just after you really needed it.


                    • #11
                      Excellent, looking forward to getting it to do the swop.



                      • #12
                        Originally posted by Stewbee View Post

                        Test results

                        Ok so resistance between volume pot back and 1 - 5 (based on diagram and my interpretation of how it's installed)

                        1 - 245K
                        2 - 245K
                        3 - 11K
                        4 - 7K
                        5 - 11K
                        Interpreting your results:

                        3) 4) and 5) shows the DC resistance of each pickup winding, so at least they are fine.

                        11k is compatible with Humbuckers, 7k with single coils, so far they match.

                        1) and 2) "should" show the pot resistance in parallel with at least 1 of the pickups, since there is no "OFF" switch position, so it should be "a little less than 11k" or "a little less than 7k" if any single pickup is selected or about 4k if in any setting 2 pickups are in parallel (plain Ohms Law applied to 2 x 11k and 7k resistors in parallel) BUT you only see 245k, the DC resistance of the Volume pot alone, same as measuring across the pot, so "something is not joining both circuits, pickups and controls".
                        Might be a wire, poor solder or the switch itself.
                        Since wiring of different elements to the switch checks fine, only switch itself remains suspect.


                        Any part can fail, a switch more probably so because its moved often, and its shaft can be bumped, but besides that you mentioned "the jack was somewhat rusty" ... that makes me think of humid storage place and possible corrosion.
                        After all due to the slot open to allow for switch lever movement, switch contacts are exposed to ambient air.

                        In regular Strats I have replaced rusty switches which stayed in any position you left them, just because of rust and grime.

                        In fact I was once bitterly accused by a customer for "stealing his valuable 5 position switch and replacing it with a cheap 3 way instead"

                        Fact is I *kept* his real vintage Strat switch , precisely because of the "Mojo Factor" by repeatedly squirting it with WD 40 and moving it back and forth.

                        The paper towel I put under it to catch drippings became deep orange brown, go figure.

                        Maybe it also caught all the Mojo carried away
                        Of course switch reverted to showing 3 sharply defined clicks instead of mushy "stay anywhere" as before.
                        Juan Manuel Fahey


                        • #13
                          Oh, thanks for that explanation Juan that helps, and the good story.

                          My old switch wasn't worth saving, but it actually looked ok inside which threw me.

                          Anyway I matched the wiring position like for like on the new one and ... it works fine, perfect.

                          Can't believe I got it sorted so easily, makes me want to get my dads old Strat sorted out

                          Thanks for all the help, no way could I have done it so quickly.


                          • #14
                            A bit late to the party!

                            I like the 5 way wafer switch, like used in a strat pickguard.
                            That gives you combo 2 & 4 settings.
                            Another thing that I would experiment with is the tone pot.
                            Normally one lead is left open, not grounded like the volume pot.
                            Try taking the ground off of the 3rd terminal, see which way sounds best?

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


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