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PK-88 OPERATING MANUAL
If the tests are valid, verify the signal on U12 pin 27 with an oscilloscope.
Recycle the power switch on the PK-88. Transitions on this pin
shortly after reset indicate that the PK-88 is sending data.
Verify that transitions are also present on U4 pin 13.
6.4.2
Symptom: PK-88 signs on with mutilated data
If the terminal displays strange characters, 'garbage', graphics, etc., one or
more of the following parameter values is incorrectly set and does not agree
between the terminal and the PK-88:
data rate (TBAUD)
data word length (AWLEN)
parity (PARITY)
number of start and stop bits
Set the terminal rate to 1200 baud if possible, seven data bits,
even parity, and one stop bit. These are the default settings stored in
the PK-88's EPROM.
Restart the PK-88 by cycling the power switch OFF then ON (out then in).
The sign on message should appear.
If the PK-88 still prints gibberish:
Verify that the terminal is set to 1200 baud and recycle the power
switches on both the PK-88 and terminal.
If the sign-on message still fails to appear:
Verify signals with an oscilloscope connected to TXD pin 25 of U12, the
Z8530A chip, and then at the X32 baud rate clock (38.4 KHz at 1200 baud)
on pin 14 of U12.
6.4.3
Symptom: PK-88 does not respond or accept commands.
Type a command such as MYCALL or any other command. If the default settings
are in effect, the PK-88 should echo typed characters back to the screen.
Verify that U12 pin 21 shows a positive voltage level.
If the above tests are valid:
Type any keys on the terminal and verify that data is present on U12 pin
27 and U4 pin 11.
If data is not seen, the data is not reaching the PK-88 from the terminal.
Verify J1, the cable, and U4 again.
6-6
TROUBLESHOOTING
PK88-180
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