Editing Apple Monitor III

{{Infobox computer peripheral
| name         = Apple Monitor III
| image        = [[File:Apple III with Monitor III (Apple Museum Prague).jpg|260px|frameless]]
| caption      = A Monitor III on an Apple III at the Apple Museum, Prague
| manufacturer = Apple Computer
| type         = 12-inch monochrome composite video monitor
| model        = A3M0006, A3M0039 (117 V); A3M0024 (230 V)
| interface    = Composite video, RCA phono jack
| compatible   = [[Apple III]]
| power        = 117 V AC ±10 %, 50/60 Hz, or 230 V AC ±15 %, 50 Hz; 27 W typical, 45 W maximum
}}
The '''Apple Monitor III''' is Apple Computer's 12-inch monochrome monitor for the [[Apple III]]. Its owner's manual carries a 1981 copyright and lists three model numbers: A3M0006 and A3M0039 for 117 V supplies and A3M0024 for 230 V.<ref name="om">Apple Computer, ''Monitor III Owner's Manual'', 1981, A3L0020, 030-0193-A, Specifications, p. 6. Hosted here: [[:File:Apple Monitor III Owner's Manual 1981.pdf]].</ref> The monitor connects to the Apple III's black-and-white video output with a phono cable. A microporous nylon glare filter rests in front of the screen.<ref name="om2">''Monitor III Owner's Manual'', pp. 1-5 (safety tips, controls, glare filter care and the problem chart). Second hosted scan: [[:File:Apple Monitor III Owner's Manual 1981 (second scan).pdf]].</ref>

The monitor contains a CRT. Read [[CRT Discharge Procedure]] before opening it.

== Specifications ==
<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:70%;"
|+'''Monitor III specifications (owner's manual, p. 6)'''<ref name="om" />
! Item !! Value
|-
| Picture tube || 12 in (30.5 cm) diagonal; 78° horizontal, 61° vertical, 90° diagonal deflection
|-
| Video input || Composite, 1.0 V p-p ±0.1 V, sync negative, RS-170 compatible; 75 Ω internal termination; RCA phono jack on the cabinet
|-
| Video amplifier || 50 Hz to 15 MHz ±3 dB; 16 discernible shades of grey
|-
| Vertical deflection || 47 to 63 Hz free-running; pull-in range +0 −8 Hz; linearity within 2 %
|-
| Horizontal deflection || 15,200 to 16,300 Hz free-running; pull-in range ±400 Hz; linearity within 2 %
|-
| Resolution || 700 TV lines at centre, 500 at the corners
|-
| Maximum brightness || 40 fL (A3M0006); 20 fL (A3M0039, A3M0024)
|-
| Display zone || 21.4 cm × 16 cm; 80 characters × 24 lines
|-
| Power || 117 V AC ±10 %, 50/60 Hz (A3M0006, A3M0039) or 230 V AC ±15 %, 50 Hz (A3M0024); 27 W typical, 45 W maximum; internal fuse
|-
| Dimensions || 43.7 cm wide, 27 cm high, 31.8 cm deep
|-
| Weight || 7.5 kg (16.5 lb)
|}

The power switch and contrast knob are on the front; brightness, vertical hold and vertical size are on the back, with a hand grip for lifting.<ref name="om2" />

== Hardware ==
Sams's ComputerFacts for model A3M0039 (folder CMT8-1, March 1985) describe a single main board with a regulated supply: AC fuse F901, bridge diodes D901-D904, a series regulator transistor Q901 with IC901, and a DC fuse F902. The B+ control R903 sets 11.6 V at the collector of Q901. The horizontal output transistor Q701 drives the flyback T702, which contains the high-voltage rectifier and also supplies 58.5 V through D252 for the video stage. The vertical stage is an IC (IC601).<ref name="sams">Howard W. Sams & Co., ''ComputerFacts'' CMT8-1, ''Apple Model A3M0039'', March 1985, Troubleshooting Aid and Miscellaneous Adjustments, p. 4, and Troubleshooting, p. 5 (PDF pp. 7-8). Hosted here: [[:File:Sams ComputerFacts CMT8 Apple Monitor III A3M0039.pdf]].</ref> A beam current limiter transistor (Q253) protects the screen from burning during long use.<ref name="sams" />

Apple's own schematic of the monitor is printed at the back of the owner's manual, which tells owners to keep it with the manual.<ref name="om" />

== Service by Apple ==
Apple did not repair the Monitor III in the field. Its Technical Procedures, revised in October 1988, tell the technician not to attempt any repair or adjustment: a defective unit is exchanged for one from service stock, with the customer's serialised rear cover moved onto the replacement and the failed unit returned to Apple. From June 1988 units serviced in Australia went back to Apple as complete systems.<ref name="tp">Apple Computer, ''Monitor III'' Technical Procedures, Section 1, Monitor III Exchange, revised October 1988, pp. 1.3-1.9, with the June 1988 Australian revision notice, in ''Apple Service Technical Procedures: Apple II/Apple III Archived Products, Volume One'', 072-0231 (PDF pp. 4-14). Hosted here: [[:File:Apple Monitor III Technical Procedures.pdf]].</ref> Board-level information comes from the Sams folder and Apple's schematic. See [[Apple Monitor III General Maintenance]] and [[Apple Monitor III Troubleshooting Guide]].

== Documentation ==
The owner's manual (two scans), Apple's Technical Procedures and Sams's ComputerFacts are hosted and described on [[Apple Monitor III Documentation]].

== Related pages ==
* [[Apple Monitor III General Maintenance]]
* [[Apple Monitor III Troubleshooting Guide]]
* [[Apple Monitor III Documentation]]
* [[Apple III]]
* [[Apple Monitor II]], the green-screen monitor for the Apple II family
* [[CRT Discharge Procedure]]

== References ==
<references />

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[[Category:Apple Vintage Accessories]]