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Started here....
http://ivanrichards.com.au/2011/12/16/more-about-rivera-amps-the-ninja-boost-mod/
But that article only describes the Ch.2 Ninja boost mod, the easier mod of the two. I had to scrape the bottom of the internet to find help with the Ch.1 Lead boost mod. (the bold underline sentence is the critical piece of info that allowed me to finally figure out what to do for Ch.1.
If you visit this thread over at tdpri, you can see and hear how these boost mods were done.
http://www.tdpri.com/forum/amp-tech-center/456473-rivera-boost-mods-r55.html
http://ivanrichards.com.au/2011/12/16/more-about-rivera-amps-the-ninja-boost-mod/
But that article only describes the Ch.2 Ninja boost mod, the easier mod of the two. I had to scrape the bottom of the internet to find help with the Ch.1 Lead boost mod. (the bold underline sentence is the critical piece of info that allowed me to finally figure out what to do for Ch.1.
If you visit this thread over at tdpri, you can see and hear how these boost mods were done.
http://www.tdpri.com/forum/amp-tech-center/456473-rivera-boost-mods-r55.html
Find Resistor R117 (value is 220k) on the circuit board. Note that Rivera completely replaces Resistor R117 with a one meg pot, this allows a wider range of adjustment (even to more boost than normal). However I just wanted to be able to reduce the amount of boost, so I wired the pot in series with R117. Here’s how I did it. Heat one lead and lift it up using your tweezers or a small screw driver. Take one conductor in the wire and tin the end with solder. Stick it through the hole the resistor came out of and solder it in. You don’t normally have to take the entire circuit board out to do this since it is plated through. Just make sure the wire doesn’t come back out. Another alternative is to snip the resistor lead so enough is left on both sides to solder to. The conductor could be solder to the remaining part of the leg that is in the board.
Take the other conductor in the wire and solder it to the end of the resistor. Make sure you tape off this end or use heat-shrink tubing. Finally, take the shield twist it together and solder it a ground point (I used the ring in the center of V2’s socket).
Now solder the other end of the wire to the potentiometer. Solder one connector to the middle pole on the pot. Solder the other connector to the right outside pole. Cut off any excess shield on this end of the wire. You only need to connect the shield on one end and it is better to connect it near the circuit board as the instructions indicate.
Alternate: An alternate method of doing this is to adjust the normal sound by replacing resistor R116 with a resistor and 1 meg pot. The value of the resistor depends on how close to normal you want to be able to go. To start with dead stock, use a 1.2 meg resistor in series with the 1 meg pot. This will allow you to get halfway to the stock Ninja Boost setting in normal mode. You can use a lower value for the resistor or eliminate it altogether and just use the 1 Meg pot to start closer to the Ninja sound. This makes channel 2’s normal sound more like a hot-rodded Fender sound. SRV fans might like this variation. I got this idea that from Rivera users who use Channel 2 with the Ninja always on, because they prefer that tone more. The alternate mod lets you get close to that sound all the time, while retaining a boost option.
Channel One Boost Ideas
The Channel One Boost Mod is the same as the Ninja Boost mod but the resistor is different. On an R Series amp there is no resistor. On an original Knucklehead the Boost resistor is R160. On the R Series amps (like the R-55, R-100, Suprema and Chubster), the Jake Studio Combo, Fandango and Quiana the R-160 resistor is not there. To do the Mod you’ll need to find the leg of photo-resistor PH106 that attaches to the junction of R119 and R130. This leg would go to one conductor of the wire going to the potentiometer, the other conductor of the wire goes to the junction where you removed the leg of the photo-resistor. This is not a mod for a novice as you could ruin the photo-resistor if you make a wrong connection.
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