Installing Blues Jr. Made in Mexico Mods Blues Jr. Tube Board

This mod is meant to be done in conjunction with other Fromel mod kits, though it can be done on it's own. If you're doing it on it's own please follow the directions and warnings from the Blues Junior MIM mod kit Steps 1 - 7 first before continuing on with this mod.

This tube board is not compatible with any other bias mods - Bill M, etc. If your amp has mods other than the Fromel Supreme, complete, and standby mods it will need to be returned to stock before proceeding with the tube board installation.

DO NOT REUSE THE RIBBON CABLE! We provide instructions for replacing it and can't guarantee a successful mod if you don't!

Install the 9 pin tube sockets in the tube PCB. Place something flat that will cover the tube sockets on top and keep them in place. Flip over both the tube PCB and the flat something so that the tube pins solder side of the PCB is facing you. The tube PCB should be an even height all the way across

Solder the tube sockets. Make sure that they're seated evenly.

Remove the standoffs from the stock tube PCB and install in the new PCB

There will be one standoff from the stock tube board that doesn't get used

Insert the new wires into the component side of the PCB, including the 4" wire at P1. I like to use painters tape to hold them in place while I flip it over and solder them.

Trim the ends after soldering to make sure none of the connections will short out on the chassis

DO NOT REUSE THE RIBBON CABLE! We provide instructions for replacing it and can't guarantee a successful mod if you don't!

Desolder and disconnect the two green heater filament wires WJ8 and WJ9 from the stock Tube PCB

Clip all of the ribbon cables in half, then on the main PCB cut them lengthwise all the way to the PCB separating them into two leads. Clip the ribbon cable leads extending past the pad on the solder side and add some leaded solder to the pads- makes it easier to remove without damage.

Gently tug on one of the separated ribbon cables while rocking back and forth and heating the solder connection with your soldering iron.

Remove all of the solder from the pads on the main PCB

Remove R51, R52, and C33

Remove R8

Jumper C33

Remove R54 and R55

Insert the wires coming from the Tube PCB into the solder holes on the Main PCB and solder on the tube socket side. I find it's easiest to do this by soldering a few at a time and working my way from left to right

Solder the wire coming from P1 on the tube board to the top hole of R8( top when looking at the amp from the control side)

Trim the ends after soldering to make sure none of the connections will short out on the chassis

Wiring V5 on the Cathode biased Blues JR IV's is a little different, you're only going to be connecting 3 wires. See pic.

Twist the green heater wires that you removed from WJ8 and WJ9 together and install on the new tube PCB at P5 and P6 soldering on the tube socket side