Apple Macintosh Powermac Performa 275 Service Manual
K
Service Source
Macintosh Color Classic II/
Performa 275
K
Service Source
Basics
Macintosh Color Classic II/
Performa 275
Basics Overview - 1
Overview
This manual includes
complete repair procedures
for the Macintosh Color
Classic II/Performa 275.
Figure: Color Classic II/Performa 275
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Service Source
Specifications
Macintosh Color Classic II/
Performa 275
Specifications Configurations - 1
Configurations
Standard
Options
4 MB RAM, 256K VRAM, 3.5-in. hard drive (many sizes),
internal 1.4 MB floppy drive, user-removable logic board, 9in. color display, built-in speaker and microphone, keyboard,
mouse, ADB and power cables, system software installed on
hard drive (requires System 7.1)
Memory expansion kit
256K VRAM SIMM upgrade
Apple IIe emulation card
LC Ethernet card
Math coprocessor
Anti-glare, anti-static CRT
Specifications Processor - 2
Processor
CPU
Coprocessor
Addressing
Motorola 68030 microprocessor
33 MHz
Built-in Paged Memory Management Unit (PMMU)
256-byte instruction and data caches
Socket for optional Motorola 68882 floating-point coprocessor
33 MHz
16-bit data bus
32-bit address bus
16-bit internal registers
Specifications Memory - 3
Memory
RAM
ROM
PRAM
4 MB of dynamic RAM on board
Expandable to 10 MB (100 ns or faster SIMMs)
Dual SIMM expansion slot (two 30-pin connectors)
Includes RAM disk software
1 MB of main ROM on board; 2 MB maximum of main ROM
256 bytes of clock/calendar/parameter memory
Long-life lithium battery
Specifications Memory - 4
VRAM
256K of VRAM on board
Expandable to 512K of VRAM with 256K VRAM SIMM (100 ns or
faster VRAM SIMM)
68-pin VRAM SIMM connector
Specifications Disk Storage - 5
Disk Storage
Floppy Drive
Hard Drive
Internal 1.4 MB Apple SuperDrive
3.5-inch, internal 40, 80, or 160 MB SCSI hard drive
Specifications I/O Interfaces - 6
I/O Interfaces
Serial
SCSI
Apple Desktop Bus
Two RS-232/RS-422 serial ports; mini DIN-8 connectors
One SCSI parallel port; DB-25 connector
Connects up to six external SCSI devices
Two ADB ports; mini DIN-4 connector
Maximum of three ADB devices recommended
Maximum current draw: 500 mA
(Mouse draws 10 mA, keyboard draws 25 mA)
Specifications I/O Interfaces - 7
Sound
Processor Direct Slot
Sound-input, external microphone port, 8-bit monaural sound,
sampled at 22 or 11 kHz
Monophonic sound-output jack for external audio amplifier or
headphones
Macintosh LC-compatible, 96-pin PDS expansion connector
Specifications I/O Devices - 8
I/O Devices
Keyboard
Mouse
Microphone
Speaker
Standard 80-key Apple keyboard with numeric keypad; ADB
connector
Soft power-on switch
2.5 mm travel, 18 mm vertical and horizontal pitch
Two-level tilt adjustment
Apple Desktop Bus Mouse II
New, ergonomic design
Built-in electret, omnidirectional microphone
Adjustable sound control on front of bezel
Specifications Sound and Video - 9
Sound and Video
Sound Generator
VRAM
Video Display
Monophonic 8-bit digital-analog conversion using 22 KHz
sampling rate for sound input (capable of driving stereo
headphones or other stereo equipment through the sound jack)
Standard: 256K of VRAM on board; displays up to 256 colors;
Supports 1, 2, 4, or 8 bits per pixel
Enhanced: 512K of VRAM; displays up to 32,000 colors; Supports
1, 2, 4, 8, or 16 bits per pixel
Built-in, 10-in. diagonal (254 mm), 9-in. viewable (228 mm)
screen
Trinitron CRT
512 pixels by 384 lines; 76 dpi
Adjustable contrast control on front bezel
Specifications Electrical - 10
Electrical
Line V oltage
Frequency
Maximum Power
90–240 VAC; Universal power supply
47–63 Hz, single phase
100 W
Specifications Physical - 11
Physical
Dimensions
Weight
Height: 14.5 in. (37.0 cm)
Width: 9.9 in. (25.2 cm)
Depth: 12.6 in. (32.15 cm)
22.5–23.2 lb. (10.2–10.5 kg)
Specifications Environmental - 12
Environmental
Operating Temperature
Storage Temperature
Relative Humidity
Altitude
50–104° F (10–40° C)
-40 to 116° F (-40 to 47° C)
20–95% noncondensing
0–15,000 ft. (0–4722 m)
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Service Source
Troubleshooting
Macintosh Color Classic II/
Performa 275
Troubleshooting General/ - 1
General
The Symptom Charts included in this chapter will help you
diagnose specific symptoms related to your product. Because cures
are listed on the charts in the order of most likely solution, try
the first cure first. Verify whether or not the product continues to
exhibit the symptom. If the symptom persists, try the next cure.
(Note: If you have replaced a module, reinstall the original module
before you proceed to the next cure.)
If you are not sure what the problem is, or if the Symptom Charts
do not resolve the problem, refer to the Flowchart for the product
family.
For additional assistance, contact Apple Technical Support.
Troubleshooting Symptom Charts/Video - 2
Symptom Charts
Video
Screen is black, too
dark, or too bright;
audio and drive
operate
Screen is bright and
audio is present, but
no video information
is visible
1 Adjust contrast button on front bezel.
2 Adjust brightness. Use Brightness Control Panel.
3 Check yoke cable connection.
4 Perform video adjustments. Refer to “Video” in Adjustments
chapter.
5 Replace analog board.
6 Replace CRT.
1 Perform video adjustments. Refer to “Video” in Adjustments
chapter.
2 Replace analog board.
3 Replace CRT.
Troubleshooting Symptom Charts/Video
(Continued)
- 3
Single vertical or
horizontal line is
displayed
Predominant color
tint or color cannot be
adjusted
Video
1 Replace analog board.
2 Replace CRT.
1 Perform video adjustments. Refer to “Video” in Adjustments
2 Replace analog board.
3 Replace CRT if red, green, or blue cannot be turned off using
(Continued)
chapter.
appropriate controls.
Troubleshooting Symptom Charts/Video
(Continued)
- 4
Picture breaks into
diagonal lines, or
picture rolls
vertically or
horizontally
Out of convergence
(color bleeds from
text or lines)
Black screen spots
(burnt phosphors)
Video
Replace analog board.
1 Perform convergence adjustment. Refer to “Convergence” in
2 Replace analog board.
3 Replace CRT.
Replace CRT.
(Continued)
Adjustments chapter.
Troubleshooting Symptom Charts/Video
(Continued)
- 5
Video
Screen jitters or
flashes
Out of focus 1 Perform focus adjustment. Refer to “Focus” in Adjustments
1 Verify that adjacent computer equipment is properly
2 Check that all ground cables are secure.
3 Replace analog board.
2 Replace analog board.
3 Replace CRT only if one part of display remains out of focus
(Continued)
grounded. Move electrical devices away from monitor.
Temporarily shut off all fluorescent lights in area.
chapter.
despite adjustment of focus controls to their limits.
Troubleshooting Symptom Charts/Video
(Continued)
- 6
Flashing or wavy
screen or monitor
emits high-pitched
noise
Raster size too short/
tall or narrow/wide
Linearity bad (size of
text/graphics differs
at top, bottom, or
sides of screen)
Video
Replace analog board.
1 Adjust horizontal or vertical size control. Refer to
2 Replace analog board.
Replace analog board.
(Continued)
Adjustments chapter.
Troubleshooting Symptom Charts/Video
(Continued)
- 7
Raster tilted or
shifted
Video
1 Verify that distortion is not due to environmental conditions
2 Perform appropriate geometric adjustments.
3 Perform yoke adjustment. Refer to “Yoke” in Adjustments
4 Replace analog board.
(Continued)
(move monitor to different location). Refer to “Monitor
Distortion” in Basics chapter of any large-screen monitor
manual.
chapter.
Troubleshooting Symptom Charts/Video
(Continued)
- 8
Video
Raster distorted
(barrel-shaped,
corners not square,
stretched or
compressed at top of
display, or sides not
perpendicular)
Raster not centered 1 Verify that distortion is not due to environmental conditions
1 Verify that distortion is not due to environmental conditions
2 Perform appropriate geometric adjustments.
3 Replace analog board.
4 Replace CRT (only in rare instances).
2 Adjust horizontal or vertical center control. Refer to
3 Replace analog board.
(Continued)
(move monitor to different location). Refer to “Monitor
Distortion” in Basics chapter of any large-screen monitor
manual.
(move monitor to different location). Refer to “Monitor
Distortion” in Basics chapter of any large-screen monitor
manual.
Adjustments chapter.
Troubleshooting Symptom Charts/Floppy Drives - 9
Floppy Drives
Audio and video are
present, but internal
floppy drive does not
operate
Disk ejects; display
shows icon with
blinking “X”
1 Replace bad disk with known-good disk.
2 Replace floppy drive.
3 Replace logic board. Retain customer’s SIMMs, math
coprocessor, and PDS card.
4 Replace floppy drive cable. See “Flat-Cable Assembly” in
Take Apart.
1 Replace bad system disk with known-good system disk.
2 Replace floppy drive.
3 Replace logic board. Retain customer’s SIMMs, math
coprocessor, and PDS card.
Troubleshooting Symptom Charts/Floppy Drives
(Continued)
- 10
Floppy Drives
Unable to insert disk
all the way
Does not eject disk 1 Insert opened paper clip into hole beside floppy drive.
1 To eject previously inserted disk, insert opened paper clip
into hole beside floppy drive.
2 Switch off system and hold mouse button down while
switching system on (to complete eject cycle).
3 Replace floppy drive.
2 Switch off system and hold mouse button down while
switching system on (to complete eject cycle).
3 Replace floppy drive.
(Continued)
Troubleshooting Symptom Charts/Floppy Drives
(Continued)
- 11
Internal floppy drive
runs continuously
Floppy Drives
1 Replace bad disk with known-good disk.
2 Replace floppy drive.
3 Replace logic board. Retain customer’s SIMMs, math
coprocessor, and PDS card.
4 Replace floppy drive cable. See “Flat-Cable Assembly” in
Take Apart.
(Continued)
Troubleshooting Symptom Charts/Hard Drives - 12
Hard Drives
Internal or external
hard drive does not
operate
Works with internal
or external SCSI
device but does not
work with both
1 Verify that SCSI loopback card is not attached.
2 Verify that internal hard drive has all three terminating
resistor packs on circuit board.
3 Verify that external drive is properly terminated.
4 Replace hard drive.
5 Replace logic board. Retain customer’s SIMMs, math
coprocessor, and PDS card.
6 Replace hard drive data cable. See “Flat-Cable Assembly” in
Take Apart.
1 Verify that SCSI device ID switch setting on external device
is higher than 0. Also verify that ID switch setting on
external SCSI device does not duplicate ID switch settings on
any other attached external SCSI devices.
2 Replace terminator on external SCSI device.
3 Replace SCSI select cable.
Troubleshooting Symptom Charts/Peripheral - 13
Peripheral
Cursor does not move 1 Check mouse connection.
2 If mouse was connected to keyboard, connect it to rear ADB
port instead. If mouse works, replace keyboard.
3 If mouse does not work in any ADB port, replace mouse.
4 Replace logic board. Retain customer’s SIMMs, math
coprocessor, and PDS card.
Cursor moves, but
clicking mouse
button has no effect
1 Replace mouse.
2 Replace logic board. Retain customer’s SIMMs, math
coprocessor, and PDS card.
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