Chapter 3. Service Precaution - Sharp ER-A770 Manual

CHAPTER 3. SERVICE PRECAUTION

1. Adjustment for SRN (IN-LINE) interface
circuit
If transistor Q9 in the transmitter/receiver section has been replaced
or if the SRN level requires readjustment, the following alignment is
required:
1) Tools and Instruments Required
Oscilloscope (50MHz or better)............................................1
ER-A770 ..............................................................................1
2) Dummy Network Specifications
R1 100ΩJ (1/4W carbon)
R2 150ΩJ (1/4W carbon)
C1 0.01µF(mylar firm)
Fig. 1 Dummy network
The oscillator should be connected to the points indicated by
.
: Connect the positive side of the oscillator.
: Connect the negative side of the oscillator.
3) Connections
Main PWB
Fig. 2
Attach the BNC connector to the SRN connector (CN7) on the main
PWB.
4) Alignment Procedure
When Using an Oscillator
a) Checking the 1MHz oscillator output
Using an oscilloscope check the 1MHz oscillator's output waveform.
5V
0V
0.5µS 0.5µS
Fig. 3 1MHz oscillator output waveform
NOTE: The oscillator used should have an output impedance of
50 .
b) Connecting the oscillator and its adjustment
Connect a dummy network or branch-trunk network to the output of
the SRN connector (CN7), and connect the oscillator to the dummy or
branch-trunk network.
R2
R1
C1
BNC connector
Waveform adjustment
Adjust VR1 until the signal waveform as shown in Fig. 4 is obtained
across TP1 and TP2 (GND).
Turning VR1 clockwise extends the interval of T1.
T1 T2
T1=580 to 620ms
T2=380 to 420ms
Fig. 4 Receiver regeneration waveform (with dummy network)
and
2. IPL (Initial program Loading) function
1) Introduction
The application software of the ER-A770 written in the flash ROM.
In the following cases, writing procedure of the application software
into the flash ROM is required
When the flash ROM is replaced with new one. The service part
flash ROM does not include the application software in it.
When IPL writing is required because of change in the software.
The service part ofthe main PWB unit includes the flash ROM with
the application software written in it, and there is no need for
writing the application software when replacing the main PWB unit.
2) IPL procedure
There are two ways of IPL procedures.
IPL from P-ROM via ER-A7RS
IPL from PC communication (Please refer the next section)
The detailed descriptions on the above procedures are given below.
TP2 TP1
Fig. 5 Board location
VOH
VOL