Kurzweil K2600 Series, Service Manual

Page: 95 / 172

Troubleshooting
Power Up Problems
5-9
Power Up Problems
Dead, No Power
1. Before opening the unit, verify the following:
• The AC cord is good and properly connected to the unit.
• The AC outlet is supplying power.
• Check the fuse located in the AC entry module. If the fuse is blown, replace it. (Refer
to Chapter 6,
Parts Lists to verify the correct value of the fuse for the unit you are
servicing.
2. Refer to the Power Supply Board schematic. Check all supply voltages.
3. Refer to the Interconnect Diagram. See page 5-14 for keyboard models or page 5-15 for
rack models. Check all related connections.
Blue Screen
1. Check the LCD Contrast pot in the scanner circuitry.
2. Check the stranded wire cable at J108 on the Power Supply Board. This cable connects to
the scanner circuitry. Its destination depends on the K2600 model you are servicing, refer
to the following note.
Note : If you are servicing a K2600R rack unit, this cable connects to J701 on the Front
Panel/Scanner Board. If you are servicing a K2600 keyboard, this cable connects to J709 on
the Scanner Board.
3. Check the fl at ribbon cable from the LCD Board to J804 on the Engine Board.
4. Disconnect and reseat the cables.
5. Check the solder connections.
6. On the Engine Board, check the signal paths and supplies for the components at the
following locations:
• Check U10 (74HC245).
• Check the supplies and crystal signals for U1 and the Flash ROMs, U4 and U5.
• If the unit does not have a Digital I/O option installed, remove the jumper pin on
JP803.
• Check the continuity between J814, Pin 8 and R149 (opposite side of designator
silkscreen). R149 is a small surface-mount resistor located on the component side near
the DAC connector.
• Check Y1 crystal.
• Check buffers U8, U12, U34 through U39. These buffers are connected to U3,
microprocessor.