ATARI ASTEROIDS DELUXE User Guide

ASTEROIDS DELUXE

SIGNATURE ANALYSIS

GUIDE

Introduction

This guide is intended as an aid to troubleshooting the Asteroids Deluxe video game PCB.
The Signature Analyzer used to produce this guide was an HP5004a. If it is found that the
signatures hold up for other makes/models of Signature Analyzers then please let me know
and I can add some kind of compatibility list to the document. Suggestions of any kind to
improve this document are always welcome.

To get the most out of the guide you’ll need

Signature Analyzer (HP5004a)
Schematics for Asteroids Deluxe
6502 NOP card (See the separate document 6502NOP for instructions on how to build
your own NOP card)
IC Clips
Some jumper wires (3 or 4 should be sufficient)

The scope of the guide is limited in that it will not enable you to fault find the entire PCB. It
should, however, be good for the following sections of the PCB:

Address Bus Buffers, Address Decoding Circuitry, Clock Circuit, Program ROMs and
Data Buffer, Vector Generator Address Selector, Vector Generator RAM Select, Vector
Generator ROMs and the Vector Generator Data Buffer.

The Clock Circuit test is very limited. The reason being is that I much prefer to check the
clock chain with a scope. If you want to figure out the signatures for the Clock Circuit then
pass on the information and I’ll include it in the document. If you want a detailed description
of these sections (and more) please refer to the Asteroids Deluxe schematic / drawing
package.

Using The Guide

For those of you who have used Atari Signature Analysis guides before then this should look
familiar and there’s probably no need to read through this section. For the rest of you,
here’s a quick run down. Every section should start with the settings for the Analyzer,
something like this

A. SA Settings for xxxxx Test

Probe Trigger IC Pin Test Pt.

Start +ve C2-25
Stop -ve C2-25
Clock -ve C2-39 φ2

The probe column refers to either the Start, Stop or Clock probes from the Signature
Analyzer.

The trigger column sets up the Start/Stop/Clock buttons on the front of the Analyzer. I have
used –ve to indicate the negative going edge of the pulse (or the falling edge).
I have used +ve to indicate the positive going edge of the pulse (or the rising edge).
The IC Pin column refers to the point where the appropriate probe should be attached.
The Test Pt. column refers to an equivalent Test Point on the boards where the probe may
be attached.

For example, in the example above the Start probe should be connected to pin 25 of IC
C2. The Start button on the front of the Analyzer should be in the fully out position to
indicate a positive going edge. Similarly, the Stop probe should be connected to the same
IC/Pin as the Start probe but the Stop button on the Analyzer should be pressed in to
indicate a negative going edge.

The section immediately following the set up procedure contains the signatures for that part
of the test. The same structure for the Set Up was employed as explained below.

B. Signatures

Logic Probe Signal Signature
On IC/Pin Name

C1-20 +5V 0003
C1-9 AB0 UUUU
C1-12 AB1 FFFF

Here, with the Analyzer probe on pin 20 of IC C1 you should get a reading of 0003. On
pin 9 of IC C1 you should get a reading of UUUU. And so on.

A signature denoted by an (*) indicates that signature may be unstable. Try taking the
signature with a 1Kohm resistor connected between the probe tip and +5V.

Down To Business

One of the things I like about this testing method is that you don’t need to have the PCB in
the cabinet. If you prefer to work in the back of the cabinet then that’s fine. If you have a
bench/test area with a +5V PSU (as I’m sure most of you have), then you can sit
comfortably at the bench. Simply connect Ground (pins 1 and 22 on the edge connector)
and +5V (pins 2 and 21 on the edge connector) to the PCB and you’re ready to start.

Just set up the Analyzer as indicated and start probing for those signatures. Always
remember to have the Watchdog disabled as this will lead to permanently unstable
signatures.