1URack_8Input_AB_2Output_Mixer
Eurorack-compatible 1U 8-channel mixer with selectable A/B outputs.
Assembly Instructions:
A. Resistors
1) 8 x 2K2 on all R_LEDX positions (R_LED1 - R_LED8) 2) 8 x 10K on all R_ChannelAB_OAin_RinX positions (R_ChannelAB_OAin_Rin1 - R_ChannelAB_OAin_Rin8) 3) 2 x 10K on R_ChanA_OAin_Rf1 and R_ChanB_OAin_Rf1 4) 2 x 22K on R_ChanA_OAout_Rin1 and R_ChanB_OAout_Rin1 5) 2 x 1K on R_ChanA_OAout1 and R_ChanB_OAout1
B. Capacitors
1) 2 x 100nF on C_ChanA_POSBY1 and C_ChanB_POSBY1 2) 2 x 100nF on C_ChanA_NEGBY1 and C_ChanB_NEGBY1 3) 1 x 100nF on C_PW_BYNEG1 4) 1 x 100nF on C_PW_BYPOS1
C. SOIC components
1) 2 x TL072 on U_ChanA_OA1 and U_ChanB_OA1
D. ThroughHole Components
1) Solder one fader per section (1-8, A and B). Will only fit one way 2) Solder one Jack socket per section (1-8, A and B). Will only fit one way 3) solder one switch per input section (1-8). Orientation does not matter. 4) Solder pin headers in the power supply holes (2x5).
Troubleshooting:
- Signal check:
Run a VCO signal into each of the inputs and check the signal at both outputs. You can use either an amplifier or an scope at the outputs. It can be helpful to draw a 2x8 grid for the inputs/outputs so you can mark each one in turn as you check.
If any of the inputs fail to produce a signal at an output then check that input section. If no signal appears at one of the output then check that output section. See below for further checks....
- Visual Inspection:
Most problems will arise from bad solder joints on the SMT components so be sure to make a final visual inspection when done. You might find it easier to do this after cleaning the flux off the pcb first. If in doubt retouch the solder joint.
- Electrical check:
Check for +/-12V voltages at the power supply pins. Also check pins 8 (positive) and 4 (negative) on the two SOIC TL072 OpAmps.
Use a DMM to check the continuity between component pins.
Check the resistance on pins connected to each resistor after soldering. If you get an open circuit reading then resolder the component. Seeing a resistance value significantly less than marked, can be a sign that another component has bad solder joints.