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6. Troubleshooting of MODEM printed circuit board
6.1 Demodulator
Preparation
(1) Set the MODEM selector on the back panel to INT side.
(2) Connect AFSK OUT TX and AF OUT on back panel.
(3) Set RX/TAPE selector on front panel to RX position.
(4) Set the other switches on the front panel to be ready to send and receive in RTTY mode.
(5) Feed CTR+E from keyboard, and set in echo-back mode.
(6) Transmit RYRYRY from keyboard.
In this operation, a self-diagnosis loop is made.
In normal state
Regardless of the selected position of RX/TAPE selector on the front panel, transmission
and reception are formed in loop, and RY signals are sent and received. (However, it is all
right if 300-baud signal is not formed in normal loop in TAPE position.)
In MODEM board trouble
When the RX/TAPE selector on the front panel is at RX, a normal loop is formed, but when
at TAPE side, normal loop is not made.
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