Problem with second-hand amp.

Posted by Arthur Payne on April 1, 2019 at 7:28am

 Hi All,

I have a query about an amplifier I have just acquired, a second hand Roland Cube X20 . It’s in really good condition and all it’s features work fine but when I plug in the jack, before it’s connected to the guitar, I get a distinct hum. This almost disappears when I hold the the other end of the lead - except if I touch the jack tip – then it really screams.

The hum also almost disappears if I touch any metal part of the amp.

When it’s connected to the guitar the hum is still there but not so obvious when it’s being played.

I don’t know much about amps or electronics but I feel that the amp may have an earthing issue. Then again, it might be quite normal. This is my first experience with an amp so I really wouldn’t know.

Any help/suggestions would be greatly appreciated

Regards

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Replies

  • Paul Craig April 1, 2019 at 5:39pm

    Since it's making a good bit of racket before the guitar is plugged in, I think your problem is the cord or amp jack being loose or bad ground connection at the jack. It's not uncommon to get a little noise in tube amps, but solid state shouldn't have that problem. So if the amp's jack is tight, try another cord before doing anything else.

    • Arthur Payne > Paul Craig April 2, 2019 at 6:00am

      Many thanks to all for their suggestions.   Yes, it was the cord.   A quick solder job and all is fine.

  • the anonymous pick April 1, 2019 at 8:13am

    Easy steps first .  You may get alot of suggestions here ,  some involving taking the amp apart etc .. before you  try any of this , try plugging it into a different location in the house .(or extension cord to another outlet) many things can effect the amp . including  lighting and other outside influence .  a simple relocation may  be all it needs . 

    • BrianQ. > the anonymous pick April 1, 2019 at 3:08pm

      Yes pick, all amps made in the last 30yrs are specifically made to not have grounding issues. with that said, check the obvious: Guitar wiring-pickups,switches,pots&output jack. Also check your cable, this is why people spend too much on cables-less money- problems, more money-less problems, cheap or failing cables make lots of noise! unscrew the ends & see if the wire has breaks- this is usually the cause? Check the outlet you are using- it may have a ground problem, this is why I always use a quality power strip & never straight in the outlet (pro tip) Lighting ballasts also make noise. Good luck, it doesn’t sound like you’ll need to take that amp apart, that’s a bad idea if you don’t know what you’re doing & could end up costing you to get it fixed? 

  • Edgel R Gillespie II April 1, 2019 at 7:42am
    Last time I had a similar problem like this, I went through all the grounds first. Meaning, the first ground was the output jack on the guitar. That fixed one situation. The next problem was the cord, I resoldered both plug heads on the cord I was using. And then the third problem was actually a wall Sounder joint on one of the points. If your shop has a chip in it, the chip might be bad. But going over all the grounds is the first step I have found, in most cases if the problem. It takes time to find to weak connection. Good luck
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