Tweet
Last year I decided I was going to build a JCM 800 2204 type amplifier & was going to build it in a JTM 45 size chassis. I was going for the lowest (not necessarily cheapest) cost. For the chassis I purchased the surplus 6Mx style available from Weber Speakers; https://taweber.powweb.com/store/chassis/chord2.html. This has holes pre-drilled and worked for my purposes.
Long story short I built the thing & it worked. This year I decided for aesthetic reasons I wanted to put a faceplate on it. I realized the pre drilled holes were off from the JCM 800 faceplate I purchased to I needed to move the input jacks & all controls over one space, including drilling new input jack holes where the original preamp volume control was, no big deal, or so I thought. After moving every front panel item over I found that the new input jack position was directly over the preamp tube socket, which made things a little too tight. I had to fabricate a new preamp tube hole and move all of the wiring for v1 to the right of the input jacks when viewed from the front. (this weber chassis has 2 preamp tube sockets in the front of the amp).
Put everything back together & tried it out. It worked, but now I had this terrible noise in the background. "This didn't happen before?", I thought. I went over the grounding scheme, examined every connection, scoured this forum for hints on why I now have this terrible 60 cycle hum that makes my amp unusable.
I was stumped. Several days later I moved the amp from one table to another to make room for another project. One day I just happened to plug it in while in the new location & realized my problem. I was simply sitting too close to the transformers when checking out the amp originally! No wonder why my telecaster was making so much noise. I believe I get the 'duh' award for that.
Long story short I built the thing & it worked. This year I decided for aesthetic reasons I wanted to put a faceplate on it. I realized the pre drilled holes were off from the JCM 800 faceplate I purchased to I needed to move the input jacks & all controls over one space, including drilling new input jack holes where the original preamp volume control was, no big deal, or so I thought. After moving every front panel item over I found that the new input jack position was directly over the preamp tube socket, which made things a little too tight. I had to fabricate a new preamp tube hole and move all of the wiring for v1 to the right of the input jacks when viewed from the front. (this weber chassis has 2 preamp tube sockets in the front of the amp).
Put everything back together & tried it out. It worked, but now I had this terrible noise in the background. "This didn't happen before?", I thought. I went over the grounding scheme, examined every connection, scoured this forum for hints on why I now have this terrible 60 cycle hum that makes my amp unusable.
I was stumped. Several days later I moved the amp from one table to another to make room for another project. One day I just happened to plug it in while in the new location & realized my problem. I was simply sitting too close to the transformers when checking out the amp originally! No wonder why my telecaster was making so much noise. I believe I get the 'duh' award for that.
Comment