DRAGON'S LAIR / SPACE ACE OPERATOR CONVENIENCE PANEL (Volume Controls) PINOUT
Written by Shaun Wood - 23 June 2021
This document details an error in the original Dragon's Lair and Space Ace main wiring harnesses.
YOU SHOULD CONTINUE TO REPRODUCE THIS ERROR IN ALL NEW BUILDS AND REPRODUCTIONS OF THIS HARNESS.
The fix below is simple, and it will be much less confusing in the future if all newly made reproduction harnesses remain identical to the original.
The best solution is to instruct the end user to swap the connections at the potentiometer (no tools needed), as shown below.
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 two purposes:
IMAGE 1 - "Original" factory wiring for Dragon's Lair volume controls
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, the potentiometer varies 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 any work done and for any damage. Follow this guide at your own risk, and... ENJOY THE GAME!
QUESTIONS? COMMENTS? PROBLEMS?
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