Kurzweil PC88 - Credits

Chapter 2 Diagnostics
NVRAM Test
This test checks that the values in the microprocessor
RAM are those left by the RAM test. The NVRAM Test is
intended to confirm the operation the memory protection
and power circuitry. In order to accomplish this, one
should completely run the RAM Test, then remove
power from the unit for several minutes. Turn power on
while simultaneously holding buttons 1,2, and 3 to re-
enter diagnostics, and select the NVRAM Test.
Failure of this test indicates a failure of the memory
protection and power circuitry or PSRAM.
MIDI UART Test
This test performs a loop-back test of the serial port by
sending a 23-byte pattern over the external MIDI link.
This test requires a MIDI loop, connect a MIDI cable
between the MIDI In and MIDI Out connectors.
Failure of this test could be caused by a the failure of
the serial port, other MIDI circuitry.
On the Engine Board check the following: U5, R40,
R47, R46, R49, C67, C68, C69, C1.
On the I/O Board, check U1, PC910, and associated
components at MIDI Connectors. Also, check the cable
between I/O and Engine Board.
Note that a short between the transmit and receive
lines could cause this test to pass falsely yet cause the MIDI
ports to be inoperative. This is probably the case if the test
passes with no MIDI loop cable installed.
PC88 Service Manual
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