Troubleshooting Microprocessors & Digital Logic (1980): Intro and TOC

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1. An Introduction to Digital Logic Techniques

Detailed IC Information-Internal Chip Circuit Diagrams-Digital Signals and Pulses-Resistor-Transistor Logic-NOR Gates- Diode Gates-Transistor-Transistor Logic-Digital Devices.

2. Microcomputer Applications and Operations

Data Processor Term-The Microprocessor versus the Microcomputer-Binary Codes-System Interfacing-Input/ Output Devices-The INTEL 8080A Microprocessor- Flowcharts-Minicomputer Speech Entry Applications- Speechlab Model 20 Hardware Operation.

3. The Microprocessor and Its Support Device

Busses-Tri-State Logic-Simple Bus System Examples-Data Storage-The Clock and Its Operation-Positive and Negative Edges-Rise and Fall Time-Propagation Delay-Clock and Trigger Pulses-Digital Waveforms and Timing-The 7490 Decade Counters.

4. Using the Oscilloscope for Digital Troubleshooting

Frequency Divider Waveforms-Divide-by-Eight Circuit Waveform-Propagation Time Measurement-Digital Circuit Time Relationship-Clock or Pulse Generation-Crystal Check Procedure-Power Supplies for Logic Systems-Microcomputer Power Supply-Lab Science VLA-1000 Logic Analyzer- Microprocessor Applications-Spike or Glitch Locator- Delayed-Sweep Scope Trace.

5. Using Logic Probes for Digital Circuit Troubleshooting

TTL Logic Signal-Ways that ICs May Fail-The Model DP-50 B & K Logic Probe-Logic Probes by Continental Specialties-DP-1 Pulse Generator Probe-Troubleshooting Gates-Logic Monitors-Hewlett-Packard Model 548A Logic Clip-Temperature Probe Applications-Handling MOS Devices.

6. Selected ICs Found in Consumer Products

GE Color TV AA Chassis-Zenith Triple-Plus Color Chassis- Zenith FM Stereo Multiplex Chip Operation.

7. TV Electronic Tuning Systems

Basic Phase-Locked Loop-Motorola IC Stereo Decoder- Additional Phase-Locked Loop Review-Checking PLL and VCO Circuits-RCA Direct Address Tuning System-FS Scan Remote Service Procedures-General Electric Remote/Electronic Tuning System.

8. Video Cassette Recorder and Videodisc Player Servicing

Sony VCR System-The Magnavox Model VH 8000 Video Player.

9. Radio Shack's TRS-80 Microcomputer

TRS-80 System Block Diagram-Isolation of a Defective Computer Section-Signal Condition-CPU Problems-Addressing Problems-RAM Problems-Address Decoder Tips-Keyboard Information-The Video Divider Chain-The Video RAM-Video Processing Problems-Sync Generator Service Points.

10. Troubleshooting Microprocessor Systems

Clocks-Power-Up Reset-Interrupts-Signal Degradation- Memory System Checks-Using Self-Test Programs-ROM Testing-RAM Testing-Multiplexed I/O-Interfaces-Troubleshooting Trees-Note the Problem-The Front Panel-Check the Manual-Types of Failures-Checking the Easy Things First-Common Production-Line Troubleshooting Problems- Board Swapping-Stress Testing Technique-Power Supply Shorts-How to Isolate the Fault-Digital Failure Modes- Isolation Techniques-Feedback Loops-Conclusion.

11. Video Games

Clock Circuits-Radio Shack Model 60-3051 Video Game-Video Game Troubleshooting-RCA Studio II Video Game-Motorola Video Modulator MC1372 Chip.


There is no doubt about it-a whole new ball-game is in progress for the electronics service technician as he moves into logic- and microprocessor-equipped devices that are now rapidly coming onto the consumer market. These items run the gamy t from digital clock timers to sophisticated video game terminals and microprocessor controlled home microcomputers.

This guide will contain practical digital/logic troubleshooting information for the electronics hobbyist. You may wish to think of this as a "service workshop in a book" about digital device servicing where we will have a meeting of the minds on these very sophisticated marvels. In fact, some of the applications the microprocessor can now perform will just about "blow your mind." Plus, almost every day some new device or technique crops up.

Two things which come to mind and are boggling at this writing are the bubble magnetic memory chip and research on ways to actually manipulate the atoms within a solid-state device to read and write back millions of memory data bytes that are nonvolatile.

This guide explains basic digital logic information and microprocessor operation, plus ways to troubleshoot them. Care has been taken in writing this guide so that the TV and electronics technician can understand these concepts and then put them into practical use.

The main purpose of this guide is to help you dig right into the digital logic operating systems and quickly locate and solve any problems. Not only will dual-trace triggered-sweep scopes and logic probes be used for these troubleshooting methods, but your own logic will be brought into play.

This guide begins with a basic introduction to digital techniques and applications. We will look at various logic gates, hardware and software. Next will be a peek at microprocessor design, programming techniques and computer language information.

Ways to use the scope for testing, (TTL) logic gates and clock pulses will be given next, along with how to capture glitches, or spikes, on a scope or logic probe. Then regulated DC power supply checks will be covered. More logic probe testing techniques follow that. How to use a probe pulser generator to jog a pulse through various gates for frame freeze time IC testing.

Then a description of various microprocessor chips found in current consumer products and ways to service them in actual bench check operations. These chips found in color TV and stereo systems will be thoroughly covered.

The guide continues by delving into operation and troubleshooting of direct address remote control color TV systems with electronic tuning. This section will also include some notes on phase locked loop (PLL) operation and testing techniques.

Moving onto another section, some selected logic circuits and ways to troubleshoot them, as pertains to video tape recorders (VCRs) and videodisc players, will next be encountered. Home and hobby microprocessor-based minicomputers systems will be next on the agenda, and we will look at some actual operations and system diagnosis.

The next item to be dealt with is video TV games. This will include game operation, service tips and how to troubleshoot video TV games.

Also see:

50 CMOS IC Projects

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This page was last updated: Friday, 2007-07-20 17:18,Wednesday, 2023-12-20 12:16 PST