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Vox Valvetronix AD120VT power selector

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  • #1

    Vox Valvetronix AD120VT power selector

    Hi,
    A friend of mine owns an AD120VT ( I own one too ), and he was complaining about audible power losses while playing. I opened it ( after fixing mine I already knew what mess I would have found inside; Enzo is right when he says they're awful to fix ) and I was able to pinpoint the reason for this behavior:The ( output ) power selector is defective, its contacts don't work properly.

    I would like to know if someone can indicate a suitable ( dimensionally and electrically speaking ) replacement, and where it could be found.

    Thanks to all in advance and best regards

    Bob
    Last edited by Robert M. Martinelli; 02-09-2009, 07:45 AM.
    Hoc unum scio: me nihil scire.
    Tags: None
  • #2
    Ah geez I hate those...

    I forget, isn;t that control just a pot? Clean it a zillion times, what is there to lose?
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      Originally posted by Enzo View Post
      Ah geez I hate those...

      I forget, isn;t that control just a pot? Clean it a zillion times, what is there to lose?
      Hi Enzo!

      I knew I was touching an "uncovered nerve" of yours!

      As I said before, these amps are great as long as they work.....

      Anyway....

      nope, it's a 4 way selector ( 1+1 W, 15+15 W, 30+30 W, 60+60 W ), already tried to clean it using what I think to be the best contact cleaner in the world ( 390 CCS ) but the d@mn thing refuses to operate properly, It's mechanically out of whack, if I exert some strength on the shaft the amp gets louder, so I definitely think the selector needs to be replaced.

      I have tried to search the internet for the P/N shown for it on the AD120VT service manual, but.....nothing.

      Anyway.....thanks!

      Best regards

      Bob
      Last edited by Robert M. Martinelli; 02-09-2009, 11:11 AM.
      Hoc unum scio: me nihil scire.

      Comment

      • #4
        OH...


        It is a couple resistor ladders, so possibly there is a broken pc board connection or cracked resistor? DO resistance checks on the switch contacts, look the resistor values up in the schematic.


        I THINK the Vox part number is V904530012. That calls out a number RS-2401-156P-20 which means nothing to me. But You might look into Radio Spares.
        Education is what you're left with after you have forgotten what you have learned.

        Comment

        • #5
          Originally posted by Enzo View Post
          OH...

          It is a couple resistor ladders, so possibly there is a broken pc board connection or cracked resistor? DO resistance checks on the switch contacts, look the resistor values up in the schematic.

          I THINK the Vox part number is V904530012. That calls out a number RS-2401-156P-20 which means nothing to me. But You might look into Radio Spares.
          Hi Again Enzo,

          Unfortunately I'm pretty sure it's the selector itself, as I told you it's mechanically out of whack ( the shaft has some axial "play" and when I move it there's an audible volume change in all the positions ) the resistors and the PCB/solder joints are OK.

          I looked into the RS catalog but, guess what, no luck.....I think I will have to take it off and try to see if I can fix it, but I'm no surgeon .

          Thanks!

          Best regards

          Bob
          Last edited by Robert M. Martinelli; 02-10-2009, 07:26 AM.
          Hoc unum scio: me nihil scire.

          Comment

          • #6
            The mechanical thing was why I suggested cracked somethings. Pressure on the shaft will also transfer to the surrounding board and connections. If it isn;t, it isn;t. I was hoping to spot something simple for you.

            Same thing with the RS. Probably just coincidence.

            Is there any possibility of ordering Vox parts where you are? Have you contacted Vox to see if you could chat someone up and ask who makes that part for them. Maybe tell them you can't seem to find someone to supply the part, maybe Vox would throw one in the mail to you?
            Education is what you're left with after you have forgotten what you have learned.

            Comment

            • #7
              Hi Enzo,
              yeah, I've been dealing with the Murphy's law a number of times lately.....

              I have read terrible stories about Vox's customer support, I've visited their site and there's not even a link for contacts or customer support....they only have a list of local representatives...looks like they don't want to have a direct contact with customers, which is pretty bad news for a Vox enthusiast like I am.

              I'll try to contact their local rep, but I'm also going to search for a suitable replacement...even if I don't find a "direct" replacement, chances are I can find something similar and make it fit ( I have a 1/2 lb. hammer that could do the job easily enough ).

              Thanks for your time and help.

              Best regards

              Bob
              Hoc unum scio: me nihil scire.

              Comment

              • #8
                Well, the switch itself is just a 2P4T rotary, right? Current and voltage handling needs are minimal. Should be able to find a small rotary switch. All we have to deal with then is the physical fit.
                Education is what you're left with after you have forgotten what you have learned.

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                • #9
                  Originally posted by Enzo View Post
                  Well, the switch itself is just a 2P4T rotary, right? Current and voltage handling needs are minimal. Should be able to find a small rotary switch. All we have to deal with then is the physical fit.
                  Yup, that's exactly when the hammer I was talking 'bout will come handy.....
                  Hoc unum scio: me nihil scire.

                  Comment

                  • #10
                    PCB rotary Sw Vox amp

                    Hey guys... I know this is an older thread, but did anyone ever find that switch part for the Vox AD 60/120 amps? I recently acquired one in need of (several) repair problems, and this is my last part needed. RS2401-15SP-20 the power out selector. This is just simply a cheap switch component in my opinion, and one that probably shouldn't even be replaced. Oh well, I thought I would give it a shot before I just fix the output at the 60 watt max setting.

                    msjulstad@gmail.com

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                    • #11
                      You can order it from any MArshall dealer or from marshallparts.com
                      Education is what you're left with after you have forgotten what you have learned.

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                      • #12
                        Thanks!

                        Many thanks, I appreciate it!!

                        soundzz

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