Tandy 1400LT - IV-20. Power Supply System

IV-20. Power Supply
The system DC power supply has an approximately 13 watt, 4 Voltage-level regulator. It is integrated into the
system unit and supplies power for the system unit, External keyboard, and its option.
The supply provides 2.5A of +5VDC
+ 1% or -5%, 60mA of +12VDC f 5%, 60mA of -12VDC f 10% and
20mA of -15VDC
f 10%.
The system unit takes approximately (0.3) to (1.8)A
of + SVDC, thus allowing approximately (0.7) A of +5VDC
for the adapters in the Exbus slot and modem slot. The
+ 12VDC and -12VDC are used for powering the
Electronic Industries Association (EIA) drivers for the communications and analog circuits, in the main PCB. The
-15VDC level is used for LCD bias.
Output control
Control 1
: +5V
Control 2
: +12V, -12V, +15V
- High ON
-Low ON
Input Requirements
The normal power requirements are listed below.
Input Voltage
Normal input 15V DC
Minimum input 13.5V DC
Maximum input 20V DC
Input requirement
Current 700mA at 15V DC
outputs
Voltage Max. power (Amp.) Regulation
+ 5v 2.5 A +1% or -5%
+ 12v 0.06 A +5% or -5%
-12v 0.06 A + 10% or -10%
-15V
0.02 A +lo% or -10%
EL Invertor
1. Output voltage frequency
Input Voltage
- 12V = 116V, Vrms = 328Vp-p : 580-700Hz
- 15V = 140V, Vrms = 396Vp-p : 580-700Hz
2. Output waveform
EL OUTPUT
Output level and frequency vary from unit to unit.
Figure 4-45. EL Output Waveform
4-55