Lexicon MC-1, Service Manual

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MC-1 Service Manual
5-2
VFD Display:
The front panel VFD display is the primary source of information during diagnostics. The exact display
information will depend on the test or tests being executed. When an individual diagnostic test is executed,
the VFD will display the name of that test. Groups of tests, such as during power on diagnostics or burn in
loops, will have a generic message on the top line of the VFD, e.g. DIAGNOSTIC TESTS, when the tests
are being executed. Any failure message will display an E followed by a number that indicates which test
failed.
Front Panel LEDs:
The test number associated with any particular test will also be displayed on the front panel LEDs. The
LEDs will be used in binary format with the MUTE LED as the LSB and the red TAPE LED as the MSB.
Running test number 1 would illuminate the MUTE LED only with all the others off. Running test number 2
would illuminate the BYPASS LED only with all others off. Running test number 3 would illuminate the
MUTE and BYPASS LEDs together with all others off, etc.
If a failure occurs, the red VCR LED is illuminated to indicate the test failure, and the LEDs indicating which
test was running when the failure occurred would also be illuminated. The diagnostics will attempt to
continuously execute the failed test, a test loop, to keep the signal lines active as an aid in debugging the
failure. Due to the MC-1 design of scanning the front panel LEDs, the diagnostics running the test loop, and
reporting the failure once during the loop, the LEDs on time is reduced. This results in the LEDs flickering,
and is normal operation.
Serial Debug Pot:
The Serial Debug Port is available to provide diagnostic status to be viewed on an external PC through one
of the serial ports on the PC. On the rear of the MC-1 is a 5-pin din connector. Pin 4 of the connector is
wired to the serial debug port. Using a terminal or a PC running a terminal program at 19.2kbs, the progress
of the diagnostics can be monitored and test failure information is reported. Also, the error log can be
dumped to the serial debug port, while in EXTENDED DIAGNOSTICS, via the remote
SHIFT/ON key
combination.
Error Log:
An error log, or ring buffer, containing a log of the last 20, 13h, failures is available. If the error quantity
exceeds 20, additional error messages will be stored at the first location in the buffer (FIFO). The error log
is stored in the non- volatile section of SRAM.
Every failure stored in the error log has 6 parts:
#NN E## tXX aYYYYYY
wZZZZZZ rQQQQQQ
1. #NN: Error Log Number: the error log location number, in hexadecimal. It goes from 00 to 13. Turning
the VOLUME knob clockwise allows one to scroll through all 20 error log locations.
2. E##: Failure Number: the E stands for error and the 2-digit number after the E indicates which test
failed.
3. tXX: Failure Type
01 = Address Failure. During an address test the data sent compared to the data retrieved does not
match.
02 = Data Failure. During a data test the data sent does not match the data retrieved.
03 = Timeout Failure. The device being sent data does not return any ready or data transfers
acknowledge.