Overview

The remote mixer PCB kit was developed to eliminate the possibility of clicking sounds that can couple into the output of the x0xi0 though the mixer circuitry as a result of its close proximity to various gate and trigger signals. This happens because the x0xb0x mainboard and x0xi0 top PCB are placed very close together. The installation of the PCB kit simply moves the location of the mixer circuit away from the trigger and gate circuitry. The kit should be installed with both the stock x0xb0x mainboard and the custom version.

 

Preparation

The tools required for installing the mixer kit are a soldering iron, desoldering tool, cutters or shears, and patience ;) The kit contains all new parts so you are not burdened with having to save all the parts from your original x0xb0x mixer circuit if they are already installed.

 

Step 1. Remove parts from existing mainboard mixer circuitry

(If working with a new mainboard PCB skip this step)

If you are working on a mainboard that has already been stuffed you will have to remove the following components from the mixer circuitry before continuing.

 

  • R136
  • R153
  • R154
  • R155
  • R156
  • R157
  • R158
  • R160
  • R161
  • R165
  • C52
  • C53
  • C56
  • C58
  • C59
  • Q33
  • Q34

 

After removing these parts it’s a good idea to clean the PCB in this area before continuing. It should look like this (stock mainboard & custom mainboard):

 

 

 

Step 2. Assembling the new mixer PCB – Resistors

The mixer PCB has the same part designations as the original mainboard parts so the part numbers follow the same designations. Install the resistors first:

 

  • 100 Ohms - R136
  • 1k Ohms - R161
  • 10k Ohms - R157, R158, R160
  • 47k Ohms - R155
  • 100k Ohms - R153, R154, R156, R165

 

Step 3. Assembling the new mixer PCB – Capacitors

If you are installing your kit into a stock Pactec case you will need to be careful of the clearance of the capacitors. If you are installing the kit into the custom aluminum enclosure you can install the parts as normal without regard to clearance issues.

 

Specifically, C52, C56, & C59 should be installed with some extra lead length so that they can be bent sideways as it may be necessary during final installation:

 

 

Step 4. Assembling the new mixer PCB – Transistors

If you are installing your kit into the stock Pactec case the transistors should also be installed with enough lead length so that they can be bent as in the picture above.

 

Q33 - 2SA733(A)P

Q34 - 2SC536F

 

Step 5a. Wiring a stock mainboard

The wires included should be connected as follows:

 

  • Red wire – right pad of R157 (5.33V)
  • Yellow wire – right pad of R136 (12V)
  • Red wire of shielded cable – top pad of R161 (out to main output & headphone)
  • White wire of shielded cable – C59(-) (in from volume control)
  • Shield – pin 2 of J7 (ground)

 

 

 

Step 5b. Wiring a custom mainboard

The wires included should be connected as follows:

 

  • Red wire – right pad of R157 (5.33V)
  • Yellow wire – bottom pad of R136 (12V)
  • Red wire of shielded cable – top pad of R151 (out to main output & headphone)
  • White wire of shielded cable – C59(-) (in from volume control)
  • Shield – C52(-) (ground)

 

 

Step 6. Wiring to the mixer PCB

The small PCB is going to eventually mount at the base of the enclosure for both the stock enclosure and the aluminum enclosure, so the same guidelines apply for either enclosure and either mainboard.

 

  • twist the red & yellow wires together as you can see in the pic and make sure they are long enough to reach the bottom area of the mainboard.

 

 

  • connect the other end of the red wire to pad 6 on the mixer PCB
  • connect the other end of the yellow wire to pad 9 on the mixer PCB
  • connect the other end of the red wire from the shielded cable to pad HP on the mixer PCB
  • connect the other end of the white wire from the shielded cable to pad VR8 on the mixer PCB
  • connect the other end of the shield to pad C on the mixer PCB

 

Step 7. Wiring the remaining connections on the mixer PCB

         remove the yellow wire connecting pad B on the x0xi0 I/O PCB to pin 1 of J7 on the x0xb0x mainboard (this is the connection from the mixer output to the overdrive circuit input)

         Remove the wire connecting pad 3 of J7 from the x0xb0x I/O PCB and mainboard PCB (this is the external Mix In)

         connect the included white wire from pad B on the mixer PCB to pad B on the x0xi0 I/O PCB

         connect the included black wire from pad J7-3 on the mixer PCB to J7-3 on the x0xb0x I/O PCB.

 

Step 8a. Mounting the mixer PCB on mainboard for use with stock enclosure

        remove the 7/16” standoff and associated hardware from the lower middle mounting location of the mainboard (this applies to both the stock or custom mainboard):


 

        if using the stock mainboard remove C105 and replace with the extra 1uF cap that is included (this is used for clearance).

        install the ” standoff with the male thread through the bottom of the mainboard mainboard and connect to the 3/8” standoff on the component side:

        mount the mixer pcb component side up onto the 3/8” standoff using the smaller ” 4-40 pan head screw and lock washer included:

 

 

Step 8b. Mounting the mixer PCB on custom mainboard used with the custom enclosure

        mount one of the 5/8” standoffs from the component side with the male thread through the PCB. Secure the thread on the other side ot eh PCB with the 4-40 lock nut included.

        Place the mixer PCB over the standoff component side down and mount the second 5/8” standoff with the male thread through the mixer PCB and into the threads of the other standoff.

 

 

 

 

 

 

 

 

 

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