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SECTION FIVE:
SYMPTOM CHECKLIST


This section gives a brief summary of common problems and their most probable causes. For more detail, refer to the section of troubleshooting in this document, or the Diagnostic Cartridge Troubleshooting Guide.


5.1   DISPLAY PROBLEMS

Probable Cause

No power (check LED), bad COMBO IC, bad VIDEL IC. See Section 3.3: Troubleshooting a Dead Unit.

VIDEL IC, COMBO IC, SDMA IC, MC68030. Use diagnostic cartridge with terminal connected via RS232 port.

Bad SIMM modile, COMBO IC, VIDEL IC. Use the diagnostic cartridge.

Video cable or connector. SGC DAC, VIDEL IC. Check signals with oscilloscope.

Verify that the monochrome monitor detect bit is being 	grounded when monochrome monitor is plugged in. 	Check MFP GPIP bit 7; replace MFP.


COMBO IC. Use diagnostic cartridge.

Modulator, phase locked loop. Trace signal with oscilloscope.

Symptom

Black Screen


White Screen


Dots/Bars on Screen


One Color Missing


Monochrome Monitor Fails to Sync but Color Monitor Okay

Scrambled Screen

TV Output Bad

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5.2   DISK DRIVE PROBLEMS


5.3   KEYBOARD PROBLEMS


5.4   MIDI PROBLEMS


5.5   RS232 PROBLEMS

Probable Cause

Power supply, AJAX IC, SDMA, PSG chip, IRQ lines shorted to ground. See if Select light goes on, if not, check PSG outputs. Listen for motor spinning. If not, check power supply. Swap disk drive or try external drive. If not working, check SDMA Controller and AJAX IC with diagnostic chart.

AJAX IC, SDMA Controller, disk drive.

Data on diskette, disk drive, AJAX IC, SDMA, or COMBO IC. Swap diskette, retry. Use diagnostic cartridge to check AJAX IC, SDMA Controller, COMBO IC; replace disk drive.

Symptom

Disk Won't Boot


Disk Won't Format

System Crash after Loading Files

Probable Cause

Bad keyboard, 6850, MFP.

Symptom

Red Screen:
Keyboard not responding

Probable Cause

Bad opto-isolator chip, 6850, inverter (74LS06).

Symptom

Red Screen: MIDI Errors

Probable Cause

Bad SCC, 1489 receiver, 1488 driver, or PSG chips,
±12 VDC:DC inverting power supply.  See Section 3.12.1.

Symptom

Red Screen: SCC Error

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5.6   PRINTER PORT PROBLEMS


5.7   HARD DISK PORT PROBLEMS


5.8   DMA SOUND

Probable Cause

 Bad PSG, MFP chips.  See Section 3.17.1


Bad ASCI port cables, terminator resistors, bad LS244, LS245 drivers.

Symptom

Red Screen: Printer Error

Shadow Printing

Probable Cause

Bad SDMA Controller, COMBO IC, AJAX IC (loading the bus), 5380SCSI Controller. See Section 3.15.1

Symptom

Red Screen: DMA Error

Probable Cause

+8V regulator, ±supplies, DSP IC, CODEC IC, SDMA IC.

Symptom

No Sound