DRAGON'S LAIR / SPACE ACE OPERATOR CONVENIENCE PANEL (Volume Controls) PINOUT
Written by Shaun Wood - 23 June 2021

INTRODUCTION

It has been discovered that there is a mistake in apparently every Dragon's Lair / Space Ace main harness, and it affects the volume controls
located on the operator convenience panel (OCP) inside the coin door.

This document has three purposes:


PROCEDURE

IMAGE 1 - "Original" factory wiring for Dragon's Lair volume controls



THE FIX:
Looking at the Molex connected to the volume controls, find the wires coming from pins 5 and 6.  (see image 1 above)
On mine, one is RED and the other is BLUE.
Where they connect to the potentiometer, pull the terminals off and swap their positions.
You should then have pin-5 connected to the center lead, and pin-6 connected to the side lead.  (see image 2 below)


IMAGE 2 - "Corrected" audio wiring for Dragon's Lair volume controls

Note - This is the correct way to assemble a Volume (OCP) Harness, no matter if it is an original factory harness, or a reproduction.


THE FULL EXPLANATION

"But my game works fine.  Why do I need this?"

Good question.  The problem stems from a reversal of two pins going to one of the volume control potentiometers.
Because of this mistake, we are varying the strength of the input signal by shorting it to ground.
Yes, this certainly lowers the volume, but if you turn the volume all the way down, you have tied an active signal directly to ground with no resistance.
This is hard on the signal source and creates noise to the entire system.  Not good.

The correct configuration keeps a constant load on the signal source and varies the amount of signal going to the main board's amplifier,
and it also wires the left and right channels in the same way.


Let's take a look at the actual mistake.
Here is a diagram of the 9 pin audio Molex on the main harness side:

Note that the incoming audio signal from the laserdisc player (red) is being delivered to pin-6, and the CPU pin-16 is getting the output signal from pin-5.

Now let's look at the harness design plan as stated in the Dragon's Lair schematics...


According to the documentation, the incoming disc audio signal for the RIGHT channel enters the Molex at pin-5, and the volume out signal
leaves the Molex at pin-6, going to the main board at pin-16.
Somewhere between design and production, these two wires got reversed.

"If the mistake is in the main harness at these two pins, why not use a pin extractor and swap the wires?"

Unfortunately, pin-6 is male, and pin-5 is female, so swapping the pins would prevent the Molex from closing.

Changing the wiring at the potentiometer is easy, requires no tools, and takes all of 30 seconds.
So you should make this fix immediately on all Dragon's Lair and Space Ace games after confirming the error in the harness.

However...  You are responsible for all work you decide to do on your game.  Neither I nor the Dragon's Lair Project are responsible if you damage your equipment.
Follow this guide at your own risk, and... ENJOY THE GAME!


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