Outerworld Arcade Outerworld Arcade
Space Encounters Space Encounters

Midway Space Encounters Sound Board Repair

Space Encounters Sound Board

Triggering sounds on the Space Encounters Sound Board:

Trigging the sounds is quite easy on these boards. You can do it by touching a connected logic probe or even your finger to different locations to hear the sound.

Screech

Enemy Shot

Bonus

Saucer

Wind

Explosion

Player Shot

Crash

Repair Log

PCB #1:

Symptom: Missing Enemy Shot Sound & Explosions

Replacing the LM3900 at D1 brought back the Enemy Shot Sounds.
Replacing the LM3900 at D2 brought back the Explosion Sounds.

Symptom: Steady clicking noise related to the Enemy shot sound.

I may replace the LM3900 at E1 (the input to this sound) and see if this affects it. I can change the rate of the clicking by touching this output at E1 to the input of the LM3900 at D1.

PCB #2:

Symptom: Missing all sounds that have a noise input except the Player's shot sound which sounds like its missing its noise component.

Here's what the Player shot sound was before repair:

And after:

The noise circuit consists primarily of a 4006 at A0 and a 4030 at A1. Using a logic probe I compared a working board to this board and found the following:

4030 (A1) Bad board/ Good Board
Pin-1 = High / Pulse
Pin-2 = High / Pulse
Pin-3 = Low / Pulse
Pin-4 = Low / Pulse
Pin-5 = Low / Pulse
Pin-6 = Low / Low
Pin-7 = Low / Low
Pin-8 = nothing / nothing
Pin-9 = nothing / nothing
Pin-10 = nothing / Low
Pin-11 = Low / Pulse
Pin-12 = Low / Pulse
Pin-13 = High / High
Pin-14 = High / High

Replacing the 4030 at A1 fixed the noise circuit and the Player shot sound is now normal and all explosion sounds are present.

Symptom: Wind sound not present / static.

The output (pin 9) of the LM3900 at C2 was dead. Replacing it fixed the output (and also improved the volume of the crash sound) but the wind sound was still not present.

The 4016 was pretty rusty and using a digital multimeter I found there was no continuity present on some of the legs of the chip. By touching multiple pins with my finger I could hear the wind sound. I'm ordering a new 4016 which I believe will fix the wind sound.

Troubleshooting the GAME ON circuit

The sounds in the game can be heard during both attract mode and game mode. The GAME ON circuit controls the volume of the sounds in each of these game modes. In a properly working game, the sounds are played very quietly during attract mode and at normal volume (adjusted by the volume control pot on the board) during game play.

Poor connections or bad components on the daughter board can cause the game sounds to be stuck in either mode. The tests below on a correctly working board set should help in isolating the cause of the problem.

Space Encounters GAME ON test points on Sound Board

Sound PCB

16-pin connector - Pin 4
positive lead of multimeter
(red+black wire) [GAME ON]

12-pin connector - Pin 8
negative lead of multimeter
(green+yellow wire) [GROUND]

Results:
Attract Mode: +4.3v
Game Mode: +0.2v

Space Encounters GAME ON daughterboard test points

Then testing the other end of the same wires at the Daughterboard PCB,

23 pin connector - Pin 3
positive lead of multimeter
(red+black wire)
[GAME ON]

9 pin connector - Pin 9
negative lead of multimeter
(green+yellow wire) [GROUND]

Should have the same Results:
Attract Mode: +4.3v
Game Mode: +0.2v

Correct results here and not at the Sound Board points to a bad connection in the harness between the two boards.

If neither match begin checking ICs on the daughter board:

7417 @ A2
input pin 13, output pin 12

7404 @ A4
input pin 13, output pin 12

74174 @ A5
inputs pin 14 & 9 (?), output pin 15

Space Encounters Sound Files: