Lexicon MC-1, Service Manual

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MC-1 Service Manual
5-6
E9 AC3 MEM / DTS AC3MEM Tests
This test verifies the AC3 MEM and/or the DTS AC3MEM test is performed on their respective boards. The
tests send patterns to the 3 memory IC's on the AC3 or DTS option board. The test patterns are similar to
the test patterns that other memory sections of the unit are tested with. Data is written to and read from
memory with 55555h, AAAAAh, FFFFFh, and 00000h.
E10 DTS 56K Test
The DTS 56K Test is a SPI, (serial peripheral test), which sends a serial stream of data to the 56004 on the
DTS board. In this test the 56004 is verified to be able to boot and to pass data. The test does not fully
verify the audio processing function of the 56004. However, if the 56004 can pass this test, which also
exercises the CPU of the 56004, most of the internal workings of the chip are operational. First the 56004 is
reset and after it comes out of reset the test program is loaded. The 56004 has internal ROM so if it comes
out of reset, it has booted and completed its internal boot program. This indicates that a fair amount of its
internal circuitry is working. Then test data patterns are sent via SER_CTRL_DATA, pin 15 of the
connector, and read back via SER_RETURN_DATA on pin 21. If the data returned matches what was sent,
the test passes.
E11 RS232 Wraparound Test
This test verifies the RS232 port is working by comparing the transmitted signal (at pin 2 of J2) to the
received signal (at pin 3 of J2). If the signals are the same, the test passed. In order to test this circuit, an
RS232 Wraparound plug is needed and must be installed at the female D9 connector (J2) on the rear panel
of the MC-1 labeled “RS232”. Once this is installed, power cycle the MC-1 and verify the following message
is displayed on the top half of the VFD about 20 seconds after power up:
SERIAL PORT A PASSED
This message is displayed for about 2 seconds before entering normal operating mode. If the message isn’t
displayed, the test failed. To troubleshoot this type of failure, use the front panel buttons (except for On/Off)
or the encoder. Each time a button is pressed or the encoder is turned, a message is sent out the RS232
port at pin2 of J2. Therefore, this will activate the TXDA signal coming from U90 (Z85230) pin 16. In the
situation where the test passes, the TXDA signal is present at U90 pin 14 (RXDA) as long as the
wraparound plug is connected. Another way to test this circuit is to verify the IR Receiver (green) LED lights
briefly when a button is pressed or the encoder is turned. This approach can be helpful when
troubleshooting intermittent failures. Please note this test resides only in the power on diagnostics.
Extended Diagnostics
Extended Diagnostics contain a set of tests which check the MC-1's functionality more extensively than the
Power On Diagnostics tests, as well as troubleshooting tests which can be used to help isolate the source
of circuit failures.
The Extended Diagnostic tests are accessible via two methods. The first method is by pressing and holding
the
REC/ZONE 2 and EFFECT ▼ front panel buttons when powering on a MC-1.
The second method is to press and hold the SELECT remote key, after all the VFD segments are
illuminated, while powering on a MC-1.
Any of the above methods will display the following message in the VFD display.
EXTENDED DIAGNOSTICS
Select a Test
Once this message is displayed the front panel buttons or IR remote key can then be released.