Tin Tuirtle Design

Installing Tubes in a JMP-1

clock September 18, 2011 16:08 by author Bald Turtle

After I got in from working on the shed tonight I decided to retube my Marshall JMP-1. Its an older unit that I purchased used in 2006, and manufacture date is around 2003. It has been a great unit and I use it with my Alesis Quadraverb that is 25 years old. The JMP-1 has never been touched but when I got back from China this last time it started sounding really ragged. I had a pair of 12AX7s and decided to go ahead and pull it open to see if I could retube it.

The worst part about this job is pulling off the top to get at the board. There are 3 phillips screws in the back and on on the top that must be removed. Then you have to remove 3 allen head screws from the rack mount ears (6 screws total) before it will come loose. Once its open it is important to guard for static. I use a wrist band cause I am old school, but you can just ground to the case and should not have any problems. My JMP-1 had noname tubes tagged ECC83 so I would bet they are the original tubes. I pulled the schematic from Dr. Tube's site which is a great site for any kind of manual or tube amp schematic. I wanted to know which socket was V1 and V2. I had a Mullard 12AX7 that has some nice cleans for V1 and a Ruby Tubes 12AX7A for V2.

Once I screwed it all back together and remounted it in the rack it was back to normal. I wish my playing was good enough to really put it to the test but unfortunately I don't play enough to really do much. I will say it sounds amazing and has an incredible variety of tone. My unit runs into my PC so that I can use it for playback. I have an old, old copy of Reason that I can record with but I just never seem to have the time.

2x12 Guitar Cabinet

clock March 13, 2011 04:46 by author Bald Turtle

Put up a tab for Projects and a quick page for my 2x12 guitar cabinet.  I need to do some more work on formatting and figure out what I really am aiming for with this site, but its fun to get some pics up.



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