Apple Studio Display 17 Troubleshooting Guide

Studio Display (17-inch CRT), blue and white version (Apple Service Source)

Fault-finding on the 1999 Apple Studio Display 17 (M6221LL/A and /B). Apple's symptom charts work at module level and end with the main deflection and CRT/video board module; the chassis maker's service manual goes further, with flowcharts that name test points, voltages and components. Read CRT Discharge Procedure before opening the display, and Apple Studio Display 17 General Maintenance for the take-apart steps and Apple's voltage checks.

First checks

• The display works with Power Macintosh computers running Mac OS 8.0 or later, except the PowerBook Duo 2300.
• The cable ends in a VGA connector. Apple supplied a VGA-to-Macintosh adapter for computers with the older Macintosh video port.
• Bowed or bent raster edges, jitter and faint lines can come from metal furniture, fluorescent lights and appliances; move the display to another room to check. Use the on-screen geometry controls for small imperfections. Apple says CRTs rarely fail.
• Power light colour: the chassis manual's power-management table gives green in normal operation and amber in standby, suspend and off.

Apple's symptom charts

In every chart Apple's last cure is to replace the main deflection board and CRT/video board module and then do the diagnostic adjustments.

Apple's symptom charts, Studio Display (17-inch CRT)

Symptom	Cures in Apple's order before the module	Service Source page
No raster, LED on	1. Check all cables for bent pins; tighten the thumbscrews. 2. If the LED is amber, try a known-good monitor to confirm the computer's video signal. 3. Adjust brightness and contrast. 4. Wake a screen saver.	Troubleshooting 4
No raster, LED off	1. Press the power button; check the power cord. 2. Test the wall socket. 3. If plugged into the computer, check the computer is on. 4. Check the cable between the main deflection board and the user controls board.	5
Screen flickers	1. Check cables and thumbscrews. 2. Move the display, ideally to the middle of the room. 3. Keep other monitors at least 18 in away. 4. Set the refresh rate above 60 Hz. 5. Check again.	6
Screen blurred	At the highest resolution small text may look soft. 1. Reseat external and internal cables. 2. Adjust H and V convergence. 3. Adjust focus (the two top controls on the flyback). 4. Check focus again.	7
Screen too bright	1. Adjust brightness and contrast. 2. Check the high voltage. 3. Check the B+ voltage. 4. Adjust the Screen control on the flyback.	8
Colours too green, red or blue; screen unreadable	1. Check the video connector for bent pins. 2. Tighten the cable. 3. Try a known-good monitor on the computer. 4. Reseat the cables on the CRT/video board.	9
Rainbow effect on a full-white screen	1. Move the display away from other equipment. 2. Switch off for a few minutes, then degauss the outside with a hand-held coil. 3. Replace the CRT: the aperture grille may have been damaged by a severe knock.	10
Thin vertical lines on the screen	The fine wires of the aperture grille can stick together after cold or vibration. Tap the sides of the case firmly with the heel of the hand under the Apple logo, right then left; if needed, tap the centre of the screen through a soft cloth with a rubber mallet, gently at first. Replacing boards will not help.	10
Raster too short, tall, narrow or wide	1. Select Recall in the OSD; if the geometry worsens, reset it in factory mode. 2. Adjust width and height.	11
Raster not centred	1. Select Recall; if worse, reset geometry in factory mode. 2. Move the display. 3. Adjust horizontal position. 4. Adjust vertical position.	12

Apple's flowchart for a suspected hardware fault checks, in order, the high voltage (27 kV), B+ (180 V), heater (6.3 V) and RGB cathode voltages (65-85 V). Readings out of range on high voltage, heater or RGB mean the board module; all in range means Apple next tries the CRT.

Component-level flowcharts

The chassis maker's manual traces the main faults to components. Its test points, in the order it checks them:

Chassis manual flowcharts (PDF pp. 13-20)

Fault	Checks in order	If a check fails, suspect
No power, power light off	Fuse F901; C991 positive terminal, 318 V DC; square wave at the drain of Q902; voltages at D921, D922, D931, D924, D925 and D926	F901; IC902; IC901, Q902 or D906; the diodes concerned; otherwise IC903
Raster but no picture ("no character")	IC302 pins 3, 8 and 12 (12 V) and pin 17 (5 V); IC302 pins 2, 6 and 11 (signal from the computer); IC302 pins 29, 32 and 35; IC303 pins 2, 8 and 12; R, G and B cathode voltages	5 V or 12 V line, P302, P305; signal cable; IC302; Q330-Q332; IC303; otherwise the CRT socket
No raster, power light green or amber	Amber: signal cable P801. Green: turn the Screen control on the flyback clockwise from minimum; D925 cathode 180 V, D924 cathode 80 V, IC911 output 12 V, D932 cathode 7.2 V; IC801 (microcontroller) pin 21 at 5 V and IC701 pin 2 at 10 V	Primary circuit of T901 and T902; CRT socket or board; otherwise IC801 or IC701
No vertical deflection (one horizontal line)	IC601 pin 2 (T901 pin 18), 15 V; IC601 pin 4 (T901 pin 15), −12 V; IC701 pin 8 sawtooth	Supply lines; IC701; otherwise IC601 and the vertical circuit
Display does not enter standby	Sync at IC801 pins 42 and 1; IC801 pins 6 and 7 waveform; IC801 pins 14 and 16 at 5 V; IC901 pin 7, 15 V; B+ lines 12 V, 15 V, 80 V and 5 V	The computer; X801 or IC801; IC801; Q903 or IC905; otherwise T901
No degaussing	IC801 pin 22 at 0 V; Q915 collector 5 V; RL901; P902	IC801; Q915; RL901; P902; otherwise TH901 or the degaussing coil
No tilt (rotation)	IC201 pin 8, 15 V; IC201 pin 4, −12 V; IC201 pin 5	D922 or the 15 V line; D931 or the −12 V line; IC801; otherwise P203 or the tilt coil
No on-screen display	IC301 pin 4, 5 V; negative horizontal pulse at IC301 pin 5; negative vertical pulse at pin 10; signals at pins 13-15 when the front controls are used	P305 or IC912; Q301 or P305; Q302 or P302; IC301 or IC801; otherwise IC302

The 318 V reading at C991 is across both reservoir capacitors: C991 and C992, 470 µF 250 V each, sit in series across the bridge rectifier with 220 kΩ balancing resistors.

Flyback, arcing and high voltage

• A graphite display that arced and sparked was given a new flyback, which worked for about ten minutes before the picture collapsed. Afterwards the power light gave three amber flashes and there was no high voltage at the neck board. The owner found the horizontal output transformer shorted and replaced it, the damper diode and some high-voltage capacitors without curing it. Another owner with the same symptoms had reflowed all the joints and greased the anode cap and flyback.
• On the VCF forum, CRT repairers warn that the flyback is blamed far more often than it fails: a failed horizontal output transistor is more likely, and cracked solder joints round the flyback are common. Diagnose with a scope before replacing parts or reflowing the whole board.
• A CRT Studio Display (size not stated) that clicked while the picture slowly shrank and then jumped back was diagnosed on the VCF forum as a high-voltage discharge. The suggestions were to check the spark gap on the neck board for dust, to look for arcing under the anode cap, and to clean the cap and the glass round it before refitting it with a thin film of silicone dielectric grease.

For capacitor values see Apple Studio Display 17 Capacitor Replacement Guide and Capacitor Failure Symptoms.

Related pages

• Apple Studio Display 17
• Apple Studio Display 17 General Maintenance
• Apple Studio Display 17 Capacitor Replacement Guide
• Studio Display (17" CRT, 16" viewable image size) Service Source
• CRT Discharge Procedure