Macintosh SE User Manual download pdf

Classic Mac Tech Docs, v1.1: No warranties expressed or implied. Use at your own risk!

Classic Mac Tech Info

1.0 Introduction

Except for minor variations, the analog board for the Mac Plus described in this document

is the same as that used in earlier models (the 128K and 512K/512Ke), and contains the

horizontal, vertical, video and power supply circuits. The horizontal and video circuits are

also virtually identical to those used in the SE and SE/30, but the vertical and power sup-

ply circuits are completely different. As will be obvious from the schematics, the vertical

circuit in the classic machines makes sparse use of ICs, so it is a bit “partsy.” However, it is

a reliable design with no history of unusual problems. The power supply, on the other

hand, is notoriously prone to failure, as there is no fan inside the unit (Steve Jobs objected

to the noise, and preferred to risk overheating the machine instead).

2.0 Video Circuit

The video ampliﬁer is a simple shunt-peaked common-emitter ampliﬁer:

FIGURE 1. Video ampliﬁer

IC U2 is a quad open-collector NAND, one gate of which is connected as a simple inverter

to present the video signal to Q7 with the proper polarity (a low at J4-1 corresponds to

white). Resistor R25 is the NAND gate’s pullup resistor. Diodes CR13 and CR14 form a

Baker clamp to prevent saturation of Q7 when driven hard, thereby speeding up response.

Inductor L4 is a shunt peaking element for boosting the high frequency response of the

video ampliﬁer. Diode CR12 is a protection device, clamping the collector of Q7 to a max-

+5V

+30V

+12F

J2-9

J2-3

J2-1

J2-5

J2-6,7

J2-8

+12-15kV

R25

470

R27

220

2N3904

CR13

CR14

R14

27µH

CR12

R20

220

27µH

NE2

NE1

C15

C16C17

Note: C15-17 are

0.01µF capacitors

with 1.5kV spark

gaps

J4-1

9” CRT

CR12-14: 1N4150

(similar to 1N914)

From

horizontal

circuit

1 2 3 4 5 6 ... 17 18

Summary of Contents

Page 1 - Classic Mac Tech Info

Page 2 - 3.0 Horizontal Circuit

Page 3

Page 4 - 4.0 Vertical Circuit

Page 5

Page 6 - 5.0 Power Supply Circuit

Page 7

Page 8

Page 9

Page 10 - 6.0 Connectors

Page 11

Page 12

Page 13

Page 14

Page 15

Page 16

Page 17 - 7.3 Keyboard Repair

Page 18

Macintosh SE User Manual

Browse online or download User Manual for PC/workstation barebones Macintosh SE. Mac Plus, analog board schematic and Tech Notes [en] [fr]

Summary of Contents

More documents for PC/workstation barebones Macintosh SE

Comments to this Manuals