Olivetti PR2 plus, Service Manual

Page: 96 / 179

683311W 4-44
The MICR circuit adjustment is made using a sample check with the < character, in E13B format, called
ON US and with code 474245A.
The ON US character is printed using magnetic ink with a percentage of oxide which can differ
according to the sample check used and which is indicated on the check.
The voltage used for adjustment differs according to the percentage of oxide indicated on the sample
check and will be 1 V for 100%; 0.9 V for 90%; 1.1 V for 110%.
When using a check with a percentage of 92%, adjustment consists of using potentiometer P1 to
adjust the voltage between J1 (1) and J1 (2), making sure that the average between the two positive
voltage peaks generated by the print head is 0.92 V as shown in the following figure:
Fig. 4-5
Proceed as follows to make the adjustment:
- Switch the printer to the PR2 emulation for check reading operations
- Use the DAWRMN signal (end of magnetization) on J1 (3) as the oscilloscope trigger
- Display the TEAMP adjustment signal on the oscilloscope by drawing the voltage between J1(1)
and J1(2).
- Activate the adjustment program that sets an E13B magnetization current knowing that the head
forward path corresponds to the check's magnetization phase while the return path corresponds
to the read phase
- Turning the potentiometer clockwise increases the amplitude of the signal, turning it counterclockwise
decreases it.