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Simms Watt 100w Head

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  • Thanks for the comment HTH.
    Any recommendations for type/specs of suitable choke?

    Originally posted by Chuck H View Post
    Being as josegrad was using his as a bass amp (IIRC) a choke would seem like a better choice than a resistor.
    In theory this is a bass amp, but works nicely for guitar as well :-)

    Comment


    • While changing pots I have the impression this component got a bit too hot.
      Is there a way to test such a small cap with a normal multi-meter?
      Or would the only option to turn on the amp with the light bulb limiter in place?

      Click image for larger version

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      I'm not even sure if it is 220uF of pF...

      It is this one used in the Master pot.

      Click image for larger version

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      Update: Must be 220pF. 220uF are not in this shape as I see.

      Comment


      • Yes, it is 220pF.
        It is a 'bright' cap that allows some highs to bypass the master volume.
        If you find the amp too bright, you can leave it removed. Or you can try other values (47pF, 470pF for example) to let more or less highs through.
        It is probably ok, it should read very high or 'open' resistance on your meter.
        Originally posted by Enzo
        I have a sign in my shop that says, "Never think up reasons not to check something."


        Comment


        • Originally posted by g1 View Post
          ...It is probably ok, it should read very high or 'open' resistance on your meter.
          Yes, resistance reads very high. I'll go on and keep it.

          Comment


          • Originally posted by josegrad View Post
            Thanks for the comment HTH.
            Any recommendations for type/specs of suitable choke?

            In theory this is a bass amp, but works nicely for guitar as well :-)
            Check out this website, it shows you how to calculate the specs of the choke you’ll need (LC filter)... http://www.valvewizard.co.uk/smoothing.html

            You could just buy an off the shelf ‘choke for 100w Marshall’ and you’ll be fine. However, a little reading and calculating your requirements will teach you something and is more worthwhile imo.
            HTH - Heavier Than Hell

            Comment


            • Originally posted by HTH View Post
              I put a choke in one of mine and I’d recommend anyone doing this - I just prefer the feel.
              HTH what do you mean by "I just prefer the feel", do you mean it changes the sound somehow?

              I have these options:
              https://en.uraltone.com/electronic-c...-marshall.html

              ----

              Auch! I found 3 cold solders that were apparently causing all the clicks and noises.
              I fixed those and the amp now runs smoothly \O/

              I'm very close now with this beast, I'm planning to check the BIAS again to get a good level.

              Thanks guys!

              Comment


              • A few hours ago I decided to jumper (?) the channels. So guitar to Normal channel 1, and then cable from Normal channel 2 to Brilliant channel 2. And it worked just fine, both channels on. I put a reverb pedal in the short cable and it sounded really nice. I played for 20 minutes and switched off with no problems.

                Now I turned on the amp and the small pilot light bulb blinked a couple of times and no power on. I'm about to open it again...

                But does this ring any bells? Would this channel jumpering be the cause?

                Fuses are ok.

                When I try measure between ground and the terminal of the mains switch I don't get any reading.


                UPDATE

                Apparently the problem was a jumper that is located in the main transformer. It wasn't making good contact. After cleaning it the contact is ok and the mains seem to work.
                The amp is now playing with me, had to take the chassis two times, first time only to discover that the problem was the power cable, now this.

                By the way, the jumper is now at 200, there is another position for 240. Europe is 220, does it make any difference having it a 200 or 240?

                Click image for larger version

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                Attached Files
                Last edited by josegrad; 02-02-2019, 11:07 AM.

                Comment


                • Hello hello,

                  Itīs been almost 4 years since I manage to revive this amp with help of people in this forum.

                  The amp still works. But I feel Iīm misusing it. I donīt play live anymore, I donīt have too much time play home either. So it is just sitting there.
                  I switch it on monthly to see that it still works. Lately Iīve noticed it would probably require a proper service.

                  But this is not a home practice amp. It deserves, and probably needs, to be played loud.

                  So Iīve been thinking about selling it, but canīt make the decision.
                  Iīm sure someone would make a better use of it, but it is so hard to get rid of these things.

                  I could get a Yamaha THR or something like that, which would be much more convenient for home use for example, and still save some money if I would sell it.

                  Does it make sense to keep it just for keeping it, any experiences/comments to share?

                  Cheers!

                  Comment


                  • As soon as you get rid of it you'll probably regret it. If you on't really need the money and have the space, why not keep it. Who knows you may have someone come into your life that the amp may inspire. Hey whats that thing over there with the lightbulbs in it?
                    And thing of how you felt when you got it up and running the accomplishment you felt.
                    nosaj
                    soldering stuff that's broken, breaking stuff that works, Yeah!

                    Comment


                    • Thanks nosaj. It is so easy to convince me to keep it...

                      Comment


                      • Hello again,

                        This amp is still with me. I turn it on every now and then and use it a bit.

                        It has two channels, the second channel is fine. But on the first channel I get a very annoying radio signal, if I move the guitar around it can almost change between different radio stations.

                        I opened it again and with a wood stick I tried to locate some bad connection, but I didnīt find anything. It happens with any guitar, and the cable should not be the problem either, if it was the cable I guess it should pick radio signal regardless of the channel.

                        Does anyone have any good hint to locate the cause of radio signal coming in?

                        Thanks in advance.

                        Comment


                        • Radio interference is usually blocked by the input grid stop resistors except in extreme cases. Check to see if your input grid stop resistors are right on the tube or if (and this is more likely) there's a long run of lead wire from the resistor to the input grid. If you move the resistor to the tube pin itself it may stop the radio getting in. I think the Valve Wizard site has some good stuff on the matter too. IIRC one solution was a smaller grid stop and then a low value cap to ground. The value being such that it squashes RF but not audio frequencies.
                          "Take two placebos, works twice as well." Enzo

                          "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                          "If you're not interested in opinions and the experience of others, why even start a thread?
                          You can't just expect consent." Helmholtz

                          Comment


                          • Check that the input jack on the bad channel has a good solid ground. Sometimes corrosion builds up between the jack and chassis if that is what is used to ground the jack.
                            WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
                            REMEMBER: Everybody knows that smokin' ain't allowed in school !

                            Comment


                            • Thank you loudthud and Chuck H I will take a look at those points!

                              Comment

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