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A question for the Valve amp fundies ?

I just purchased a Marshall JVM head last night ? and plugged it into my cab (correct OHM etc)

I started to play around on it and after 10min I started to hear a crackle (almost the sound of pulling a guitar cable out while your amp is on)
I then saw some sparks / fireworks from the amp and noticed 1 VALVE was purple.

I immediately shut it off. Waited a while and swiched back on. I then noticed that that particular valve was not glowing like the other 3 and the amp had min volume.

Now my concern is that there are no heads left in stock, so I have the option for them to replace the valves, however I am concerned that there could be other damage to the amp? or will a re-tube be perfectly fine?

Many thanks



    A valve swap can maybe fix it but something else could have caused that to happen. At best you'll have to have the amp checked for other problems I think.
      Call Karel Mars, he's in Paarl.
        No! It's a brand new head!!!!! TAKE IT BACK! It won't be nice waiting for a new one but play it safe!
          Jacquesg4j wrote: No! It's a brand new head!
          He said he purchased it, he did not say from where?

          shadow1 wrote: I just purchased a Marshall JVM head last night ?
          What shop opens Monday nights?

          Why would you buy an amp like that new? ???
            Gearhead wrote:
            Jacquesg4j wrote: No! It's a brand new head!
            He said he purchased it, he did not say from where?

            shadow1 wrote: I just purchased a Marshall JVM head last night ?
            What shop opens Monday nights?

            Why would you buy an amp like that new? ???
            He did say "they" didn't have any more heads in stock??
              I did indeed purchase it BRAND new from a local music store ?

              They waited for me to get there after work. Pretty bummed about it. I am not sure what to do regarding the amp. They can sort the valves (but who says there is not something else faulty) OR they can give me the JVM 410h Dave Mustaine Signature series but this amp is not listed on Marshalls website and I am always nervous about sig series.
                Ag, let them swop the tubes, try it again... If there's something else wrong, at least you still have some sort of guarentee if it pops the tubes again!
                  Jacquesg4j wrote: No! It's a brand new head!!!!! TAKE IT BACK! It won't be nice waiting for a new one but play it safe!
                  agreed you bought it last night?................take that beeyotch back pronto.
                    THanks for the advise, I am still tossing between returning it or taking a chance on new valves, I am sure its a amp that will serve me SO WELL for what I want to do... (play various styles from hardcore to blues)
                      Can they not do the valve swap and if it goes wrong again then you take it back and wait for them to get new stock?
                        shadow1 wrote: THanks for the advise, I am still tossing between returning it or taking a chance on new valves, I am sure its a amp that will serve me SO WELL for what I want to do... (play various styles from hardcore to blues)

                        I had a brand new Marshall explode on me in the shop (Didn't know yours was new). Take it back, let them deal with it. You should be getting a pristine amplifier that should work for many years but unfortunately it seems that quality control issues are getting a bit too common of late.
                          Thats sounds like a power tube blowout..... or a rectifier...... also you fuse will need replacing probably.....
                          You dont have to take it to the doctor if its a tube issue...
                            Valves go bad - even new ones (in fact, new production are more likely to go within the first few months - if they last through the burn in, they will likely last a few years).

                            Just let them swap out the faulty valve (or set if it's a power valve). If it goes again, let them get it fixed or swap it out for something else.
                            Gearhead wrote: Why would you buy an amp like that new? ???
                            Well someone has to. WHere do you think second hand stuff comes from? ? And a lot of guys like to know the history of an amp and have the manufacturer's warranty.
                              I got a jvm and that happened to me a few weeks ago....... One of the power tubes blew out, took thanothe tube with it and a few resistors too, turns out that JJ don't handle moving around well, hap I fixed by a tech and swopped JJ's for Tung sols.
                              Let's see how they hold up to travelling.
                                Do you guys think fitting new tubes with out a RE-BIAS will be fine?
                                  BOET Really ... RE-BIAS ?????

                                  you've just been given the best advice EVER and you're worried about biasing.
                                    shadow1 wrote: Do you guys think fitting new tubes with out a RE-BIAS will be fine?
                                    If it's power valves being replaced, they must both be changed together with a matched set (two EL34s in a 50W head, four in a 100W) and the amp must be rebiased. It will probably work without rebiasing, but chances are good that it will not sound its best and also a good chance that the new valves will burn out quicker than they should.
                                      5 days later
                                      Alan Ratcliffe wrote:
                                      shadow1 wrote: Do you guys think fitting new tubes with out a RE-BIAS will be fine?
                                      If it's power valves being replaced, they must both be changed together with a matched set (two EL34s in a 50W head, four in a 100W) and the amp must be rebiased. It will probably work without rebiasing, but chances are good that it will not sound its best and also a good chance that the new valves will burn out quicker than they should.

                                      Thank you, I have chatted to the store and they are sending me a new amp (slightly different limited edition) holding thumbs that the tone is the same. Excited to finally get the amp hopefully the end of the week ?

                                      It really helps dealing with accomodating stores in cases like this.
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