Infinity Interlude Series, Service Manual, Page: 16 / 37

IL120s ADJUST BIAS PROCEDURE
(Mandatory when any output MOSFET transistors Q3,4,7,8 are replaced)
1. Amplifier should be unplugged and OFF.
2. Remove Amp assembly from cabinet; remove rear plastic cover if present. All wires exiting
the cover can remain connected unless they will prevent you from removing the amplifier or
accessing potentiometers on the Linear board PCB in the following steps.
3. Locate the Linear board assembly (PCB with the output transistors)
4. Adjust R11 and R27 fully Counter Clockwise. See diagram below.
5. Apply 120 VAC power to unit, Turn power switch ON.
6. Verify LED illuminates on the front gain control dial unless you have disconnected the plug.
7. Connect voltmeter set to DC millivolt range to twin pins on terminal J7, on Linear board
8. Verify initial voltage is less then 0.1 mV.
9. Adjust R11 Clockwise until voltmeter reads 0.3 mV + the initial current from step #8.
10. Adjust R27 Clockwise until voltmeter now reads 0.6 mV + the initial current from step #8.
11. Turn amplifier OFF. Disconnect AC power to unit.
12. Remove voltmeter from terminal J7.
13. Replace cover (if present), wires if disconnected, and replace amplifier back into cabinet.
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