Apple AppleVision 850 Display Troubleshooting Guide

Main deflection board of an AppleVision 850AV with the electrolytic capacitors marked (photo: Elemenoh, TinkerDifferent)

Fault-finding for the AppleVision 850 and 850AV (20-inch ColorSync) displays, from Apple's Service Source and from owners' repairs. Apple's manual notes that many modules returned for repair were in fact working, and asks for its first checklist to be read before anything is replaced. Cures are in Apple's order of likelihood. Allow the display about 20 minutes to warm up before judging it.

The CRT anode runs at 27 kV. Discharge it, remove the anode cap and fit an ongoing ground lead from the anode aperture to the CRT's ground strap before replacing any module; see CRT Discharge Procedure.

First checks

• The display works with computers whose video falls within 30-94 kHz horizontal and 48-120 Hz vertical; some computers need a video card.
• The raster is never a perfect rectangle, colour purity is never perfect over the whole screen, and some misconvergence is normal. Magnetised metal furniture causes bowing, bent edges and colour blotches; fluorescent lights and appliances cause jitter. If the picture changes when the display is turned through 90 degrees or moved, the location is the cause.
• A misadjusted screen can look like a failed main deflection board or CRT.
• When testing with a second, known-good monitor, do not use an AppleVision 1710 or 1710AV: the AppleVision software is not compatible between the two lines and can behave erratically.

Symptom charts

Apple's symptom charts (Service Source, Troubleshooting pp. 4-9)

Symptom	Cures, in Apple's order
Black screen, power light off	Check the power cord for damage and continuity with an ohmmeter. Check the outlet, the power switch and that the computer is on. Replace the main deflection board and adjust the display
Black screen, amber power light	Check the computer's video with a known-good monitor. Check the cables, including the ADB cable. Follow the hardware diagnosis below
Black screen or one colour, slanted horizontal lines, green power light	Check the front brightness and contrast are not at minimum. Install AppleVision software 1.5.2 or later and restart holding Command-Option-A-V. Discharge the CRT and check the CRT/video board is firmly on the CRT neck: it should not move when gently rocked, and a grinding noise from the neck means the tube is damaged. Check the red and white wires are secured in the CRT socket. Check for high voltage (a rustling sound at switch-on or off). If the set-up data can be downloaded, replace the main deflection board; if not, refer to Apple
Distorted shape	Turn the display at least 90 degrees or move it. Click Factory Settings in the Geometry section of Monitors & Sound. Adjust the AppleVision controls
Screen one colour	Check the video cable pins. Check the cable is secure. Select a standard white point (D50, 6500 or 9300) and click Recalibrate. Check the CRT/video board is tight on the CRT neck
Blotches of colour	Move the display away from external speakers and large metal objects. Leave it off for 20 minutes and retry. Degauss it with a hand-held degaussing coil. Adjust Rotate in the Geometry section
Very bright screen; display may shut down	Adjust brightness and contrast. Check and adjust the high voltage
A 2 in (50 mm) vertical bar on the right side dimmer than the rest	Check the cables. Check for interference. Replace the main deflection board
Poor focus	Set convergence in Monitors & Sound. Adjust H and V focus on the flyback. Use the utility's H-Focus control for edge focus. Check the red and white wires in the CRT socket. Adjust convergence by hand
AppleVision software not working, or the display not listed in Monitors & Sound	Reinstall the software and restart. Check the ADB connection by changing resolution from the control strip
Screen freezes at startup	Check the yoke wires to BF1 and BL1 on the main deflection board are not clamped in with the ribbon cables; separate them
Jitter or a wavy picture at 1152 × 870 on a Power Macintosh 9600	Not the display: early Apple/IMS video cards (serial below Fx705xxx) cause it; Apple replaced them with 661-1409
Two thin horizontal lines across the screen	Not a fault: the support wires of the Trinitron aperture grille

Apple also lists jitter on a Power Macintosh 5500 (serials TY705 to TY715) or Power Macintosh 6500 (XB708 to XB718), and a blurred picture on a 6500 (XB708 to XB723) at 832 × 624 and above, as faults in the computer. A 6500 should not be set above 1152 × 870.

Diagnosing a hardware fault

Once cables, power, software and the front-panel settings have been ruled out, Apple's procedure uses the Display Service Utility.

1. Run the utility, select AppleVision 850/850AV and click Create File (about three minutes).
2. If the utility cannot talk to the display, remove the housing and measure between chassis ground and the end of resistor RP128 nearest IC IP6 on the main deflection board. At 11.5-15 V, Apple returned the display for unit replacement. Below 11.5 V or above 15 V, replace the main deflection board and try again.
3. If Create File succeeds, click Adjust Geometry, which checks the high voltage, and measure it with the probe. If the high voltage is correct (27 kV), the CRT/video board is the suspect; if there is none, the main deflection board.

The high-voltage measurement is on the general maintenance page.

Faults found by owners

These are individual repairs reported on the TinkerDifferent forum, not Apple data.

• An 850AV showed a correct picture only at 1024 × 768 and 60 Hz, and a narrow, distorted raster in other modes. The secondary power-supply capacitors on the main deflection board tested good; CL43 was 22% low and was replaced along with CL6, without effect. A new TDA4858 deflection controller and new 100 µF capacitors on the neck board did not cure it, and the controller's horizontal sync input and drive output followed the resolution correctly. The fault was not found.
• Another owner reported that very similar symptoms on a 17-inch AppleVision 1710 or ColorSync 750 came from the control logic on the neck board. Replacing the capacitors in the digital section and fitting a blank 93C66 EEPROM restored a stable picture, at the cost of the ColorSync calibration: the display then works as a plain multiple-scan monitor.
• The calibration data held in the display can be reloaded from its backup copy by restarting with Command-Option-A-V; one owner warns that this can make matters worse if the backup is also bad.

Related pages

• Apple AppleVision 850 Display
• Apple AppleVision 850AV Display
• Apple AppleVision 850 Display General Maintenance
• Apple AppleVision 850 Display Capacitor Replacement Guide
• 20" ColorSync Displays Service Source
• CRT Discharge Procedure