Ac Boards; Testing The Ac-Sensor Board (Pcb B3A7Xr00); Testing And Calibrating The Ac-Control Board (Pcb B3B3Xr02) - Classe Audio Delta Series Service Manual

AC Boards

Before you begin, perform a detailed visual inspection of the AC-sensor and AC-control boards. Check for
missing components, missing solder or accidental solder bridges (especially under surface-mount ICs). Check
direction of all ICs, capacitors, and diodes, and other visible problems.

Testing the AC-Sensor board (PCB B3A7XR00)

Check all components.
Connect a tested mini-toroid transformer (ToroidTech TR0005-0015) to CON1 (primary) and CON2
(secondaries)
Insert 400mA fuse at F1
Connect Earth from AC plug to MH1
Connect 120Vac between N4 (neutral) and N5 (line)
Power-up
Verify that the voltage on pin 3 of the voltage regulator is 5.0Vdc
Verify that the first secondary of the mini-toroid (on BR1) measures 11.5Vac
Verify that the second secondary of the mini-toroid (on BR2) measures 3.3Vac
Use your oscilloscope to look at the voltage on pin6 of IC1. It should be a 60Hz square wave with 5V peaks.
Use your oscilloscope to look at the voltage on pin6 of IC2. It should be 5Vdc.

Testing and calibrating the AC-Control board (PCB B3B3XR02)

Check all components.
Turn trimpot R7 CCW to end (minimum).
Connect the AC-Control board to a tested AC-Sensor board with mini-toroid transformer (see above)
Power-up the assembly and adjust your variac to precisely 120Vac
Connect your voltmeter's ground probe to pin5 of IC2 on the AC-Sensor board
Probe test point T1 on the AC-Control board
Turn trimpot R7 CW until the voltage on T1 rises to 1.43Vdc
To test the digital portion of the circuitry on this board, refer to the following section.
CA(P)2100 AMP Service Manual v1.4 inc voltage change info .doc Page 13 of 50