Power Macintosh 5260 General Maintenance

Rear of a Macintosh Performa 5260/120, the same chassis as the Power Macintosh 5260. The I/O door gives access to the logic board. Photo: Stephen Edmonds, Wikimedia Commons, CC BY-SA 2.5

The procedures below for the Power Macintosh 5260 come from Apple's service manual for the machine, Power Macintosh/Performa 5260, 5280 Series. The 5200 and 5300 manual is titled "(not 5260, 5280)" and its procedures, board part numbers and high-voltage adjustment do not apply.

The 5260 contains a CRT and a power supply and analogue board that carry mains voltage and stored charge. Discharge the CRT before working near it; see CRT Discharge Procedure.

How Apple serviced it

Apple serviced the 5000-series all-in-ones by module exchange (p. 5). The CRT and degauss frame are matched at the factory and are replaced as one unit, and the chassis harness (metal chassis, logic board connector and cables) is a single service module. The logic board slides out of a connector like the one on the Macintosh LC 630 and LC 500 series. Apple's diagnostic for the family is MacTest Pro for Power Macintosh (p. 7).

Getting inside

Remove the drive and control bezel to reach the floppy drive, CD-ROM drive and front panel control board. Remove the I/O door to reach the logic board, hard drive and video options (p. 7). The analogue board, power supply, video board and CRT need the rear housing off. Apple's take-apart order is:

1. Drive and control bezel, floppy drive, CD-ROM drive, front panel control board
2. I/O door, logic board
3. Rear housing, front bezel, internal microphone, rear EMI shield, speakers, hard drive, TV tuner
4. Power supply, video board, analogue shield, analogue board, fan, tilt/swivel base, CRT, chassis/wiring harness

The power supply's connectors to the analogue board (P805, 10-pin; P804, 4-pin; P807, 2-pin) are keyed and fit snugly; Apple suggests loosening their sockets with a jeweller's screwdriver (p. 128).

Memory and cache

The logic board has two 72-pin SIMM slots for 80 ns or faster SIMMs, up to 64 MB. The plastic pin on each slot must engage the hole in the SIMM and the clips on both sides must snap into place (pp. 29, 158–159). The level-2 cache is a card in its own slot; its notches line up with ribs inside the slot (p. 171). Apple's specification pages list 4, 8, 16 and 32 MB SIMMs, fitted singly. The owner's manual has illustrated steps for opening the computer and fitting SIMMs and the cache module, written for users (Appendix B, pp. 136–149).

PRAM battery

Apple's specification pages give the battery type as a 4.5 V alkaline pack, and the symptom charts refer to it as the "4.5 battery". It connects to the logic board by a plug and sits on a hook-and-loop base (p. 177).

To test it, remove the I/O door and the logic board, set the meter to the 10 V DC range and measure across the battery. Apple says to replace it below 3.0 V (pp. 174–175).

Leakage from an alkaline pack is caustic. Neutralise it with a mild acid such as white vinegar, then clean with isopropyl alcohol; see Battery Explosion, Capacitor or Corrosion Damage and Battery Refurbishment.

Resets

Apple's Additional Procedures chapter has two resets to try before replacing a board. For a Cuda reset, take out the power cord, I/O door and logic board and press the Cuda reset switch on the logic board with a flat plastic tool (p. 178). The Cuda microcontroller handles soft power, resets, PRAM, ADB and the real-time clock (p. 21).

For a full logic board reset, unplug the battery as well, wait 5 to 10 minutes, plug it back in, press the Cuda reset switch and refit the board. This clears PRAM, so set the date, time and control panels again afterwards (pp. 179–181).

Adjustment controls

Apple's adjustments are made with the rear housing off and the machine running, using plastic tools only; Apple warns that metal alignment tools are a shock hazard (p. 190). Test patterns come from the Display Service Utility on the MacTest Pro CD.

5260 and 5280 adjustment controls

Control	Designator	Apple's target
Horizontal shift	R410	Raster centred left to right
Vertical shift	R320	Raster centred top to bottom
Horizontal size 2	R440	Raster width 240 mm ± 2 mm (9.5 in ± 1/8 in)
Vertical size 1	R327	Raster height 185 mm ± 2 mm (7.3 in ± 1/8 in)
Focus	On the flyback transformer	Best centre-of-screen focus
Convergence	Yv and Yhc on the yoke	Best convergence of vertical and horizontal lines at top and bottom
Pincushion	E/W 2	Removes barrel distortion
Keystone	R438	Raster the same width at top and bottom
Screen	On the flyback transformer	Left-hand grey bar solid black, next bar very dark
Red, green, blue bias	R910, R940, R970	Darkest grey bars neutral
Red, green, blue drive	R501, R531, R561	Bars shades of grey at full contrast
Sub-brightness	R500	25 foot-lamberts on a photometer (20 ± 3 on the bottom scale of an R77 meter)
Power supply	R828	110 V DC at P805 pin 3, measured to chassis

Sources: Geometry, Video and Power Supply adjustments, pp. 190–214. Apple asks for the cutoff and white-balance procedure after the display has been on for 10 minutes, and whenever the CRT or analogue board is replaced or the screen control has been moved (pp. 201–202). The power-supply adjustment must be repeated whenever the analogue board or power supply has been taken out (p. 213).

Things that are not faults

Apple's first checklist and symptom charts list several behaviours that are normal or external:

• Jitter, faint lines or screen movement can come from nearby electrical equipment or fluorescent lights. Apple's test is to move the unit to another room or building (p. 47).
• Some misconvergence is normal, especially at the edges of the screen (p. 55).
• A misadjusted screen can mimic an analogue board or CRT failure, so Apple asks for the adjustments before a module is replaced (p. 47).
• Some geometric distortion is within tolerance and "setting need not be perfect" (p. 58).
• The internal speakers mute when a plug is in an output jack (p. 35).

Capacitors

Apple's manual contains no schematics or component values for any of the 5260's boards. See Power Macintosh 5260 Capacitor Replacement Guide for the board part numbers and what to check after a recap.

Related pages

• Power Macintosh 5260
• Power Macintosh 5260 Specifications
• Power Macintosh 5260 Troubleshooting
• Power Macintosh 5260 Capacitor Replacement Guide
• Power Macintosh/Performa 5260, 5280 Series Service Source
• Hard Drive Maintenance and Repair
• Recommended Tools