Mitsubishi V20, V21 Service Manual

MITSUBISHI ELECTRIC

2003

™

own

HIGH SPEED TROUBLESHOOTING

V20 & V21 CHASSIS

V20 Chassis

VS-A50 WS-A48 WS-A65 VS-50111 WS-48311 WS-65311 VS-60111 WS-A55 WS-65411

WS-55311 WS-73411 WS-55411

V21 Chassis

WS-48511 WS-65511 WS-73711 WS-B55 WS-65611 WS-55511 WS-65711 WS-55711 WS-65712

MITSUBISHI DIGITAL ELECTRONICS AMERICA, INC.

9351 Jeronimo Road, Irvine, CA 92618-1904

Down To 1 - High Speed Troubleshooting

CONTENTS

INTRODUCTION 3

SAFETY PRECAUTIONS 4

PCB FUNCTIONS AND LOCATIONS 6

TROUBLESHOOTING CHARTS

Audio 7 Video 8 Power 10 Convergence 12

ADJUSTMENT DATA

Convergence Master 13

PARTS LIST 14

PCB FUNCTIONS AND LOCATIONS 15

TROUBLESHOOTING CHARTS

Audio 16 Video 17 Power 19 Convergence 21

ADJUSTMENT DATA

Convergence Master 22

PARTS LIST 23

V20 CHASSIS

V21 CHASSIS

INTRODUCTION

DOWN to 1 Goal: Isolate the faulty component 9 out of 10 times.

Required tools: Signal Generator such as Sencore VP300 or VP301

DOWN to 1™ High Speed Troubleshooting

The troubleshooting of any PTV chassis involves one of two methods. The first involves an exhaustive checking of all suspect DC and AC voltages, waveforms, and the like. This is all possible given the necessary time and equipment. The second occurs most frequently in field service, where time is often insufficient and equipment unavailable or impractical. It is then that all of a technician’s practical experience must be brought to bear in order to make an educated guess as to where the product failure or difficulty may lie. This second method is the focus of this publication and the DOWN to 1 discipline.

Color, Pattern and Perception

Observation is key to an overall evaluation strategy. The details gathered from a precise observation can go a long way toward arriving at a repair solution in a timely and efficient manner. With this understanding, MDEA has brought the combined technical expertise of its years to bear in creation of the DOWN to 1™ method. For simplicity and easy memorization, color, pattern and perception are employed as the primary tools.

Color

• Each component has its corresponding unique color.

Pattern

• For each troubleshooting case, the component to replace is identified by an oval color pad at the terminating end of its path.

Perception

• A perceived problem provides deductive reasoning clues to its solution.

Main Power Signal Terminal 2HDW 3DYC Jungle Conv-Gen DM Assembly

CRT(s)

SAFETY PRECAUTIONS

NOTICE: Observe all cautions and safety related notes located inside the receiver cabinet and on the receiver chassis.

WARNING:

X-Radiation warning

The surface of the cathode ray tubes (CRTs) may generate X-Radiation, so take proper precautions when servicing. It is recommended that a lead apron be used for shielding while handling the CRT. Use this method if possible.

When replacing the CRTs, use only the designated replacement part since it is a critical component with regard to X-Radiation. High voltage must be set as prescribed in the V21 Service Manual under the section titled Electrical Adjustments.

Leakage current check

Before returning the receiver to the customer, it is recommended that leakage current be measured according to the following methods.

1. Operation of this receiver outside the cabinet or with the cover removed presents a shock hazard from the receiver's power supplies. Work on the receiver should not be attempted by anyone who is not thoroughly familiar with the precautions necessary when working

on high voltage equipment.

2. Do not install, remove or handle the picture tubes in any manner unless shatterproof goggles are worn. People not so equipped should be kept away while the picture tube is being handled. Keep the picture tube away from the body while handling.

3. When service is required, observe the original lead dress. Extra precaution should be taken to assure correct lead dress in the high

voltage area. Where a short-circuit has occurred, replace those components that indicate evidence of overheating.

1. Cold Check

With the alternating current (AC) plug removed from the AC source, place a jumper across the two AC plug prongs. Connect one lead of an ohm

meter to the AC plug and touch the other lead to each exposed metal part (i.e. antennas, handle bracket, metal cabinet, screw heads, metal overlay, control shafts, ( etc.), particularly any exposed metal part that has a return path to the chassis. The resistance of the exposed metal parts having a return path to the chassis should be a minimum of 1Mega Ohm. Any resistance below this value indicates an abnormal condition and requires corrective action.

(continued next page)

SAFETY PRECAUTIONS

(continued from preceding page)

2. Hot Check ...Use the circuit shown below to perform the hot check test.

1. Keep switch S1 open and connect the receiver to the measuring circuit. Immediately after connection, and with the switching devices of the receiver in their operating positions, measure the leakage current for both positions of switch S2.

2. Close switch S1, energizing the receiver. Immediately after closing switch S1, and with the switching devices of the receiver in their operating positions, measure the leakage current for both positions of switch S2. Repeat the current measurements of items 1 and 2 after the receiver has reached thermal stabilization. The leakage current must not exceed 0.5 milliampere (mA).

V20 Chassis - PCB Functions and Locations

PCB-Terminal PCB-Signal PCB-Doubler PCB-Main PCB-Power

A/V Inputs Control uPC PIP-POP Horizontal Defl. Power Supplies A/V Selection Tuning Picture Format Vertical Defl. High Voltage 3D-Y/C VCJ 3:2 Pull Down Audio Amp. SVM NTSC Video Convergence Line Double Convergence Amps. Decoders Generator 480i to 480p DBF

V20 Chassis - Audio Problem

Audio problem

Supply

Audio

problem any

or all NTSC

sources

Main Power Signal Terminal 2HDW 3DYC Jungle Conv-Gen DM Assembly

signal to antenna

input.

Check Monitor

Output. Good

audio?

YES

PWB-Main

Supply signal to different

line

inputs

PWB-Terminal

Have audio

to speakers?

YES

PWB-Signal

CRT(s)

+ 19 hidden pages