All You Want To Know About Electrohome G07 NTSC Decoder Board (Dragon's Lair)

1kGen

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All You Want To Know About Electrohome G07 NTSC Decoder Board (Dragon's Lair)

I am always surprised when the internet is void of information on certain things. This was one of them. I am simply putting an entry in for anyone who needs to know things about this board, as it has been shrouded in mystery prior.

First off, this is only for the Electrohome G07. While this board will work with most monitors, there are other decoders out there (WG makes one as well) that only work with the specified monitor. See the pics below to understand exactly which board I'm referring to.

"Where do I plug this board in?" This board requires 16v power. It is supplied off of W406 on the G07 chassis. Usually the plug has two female prongs. One would THINK that you'd plug it into the male end of the 2 prong on the decoder board (P101). DON'T DO THIS! If you do, you'll blow a bunch of components (definitely R133 and most likely the IC chip as well). NOTHING GETS PLUGGED INTO P101. It is simply another input for video.

Power gets plugged into pin 1 on P102. Nothing else gets plugged into these prongs. The other prongs here are used to utilize a remote controller for the board (which was never used on arcade cabs). Pin 1 is the pin closet to the edge of the board. Be VERY sure you are plugging into pin 1 so you don't blow anything on the board. See the picture I'm attaching to see where to plug into.

Okay, so you've got power going to your board. Now obviously, the component cable from the LD player goes into the obvious connector. From the solder side of the board, be sure that this is still connected. A small wire should be attached to the center of the this connect and go to pin1 of P101. Nothing goes to pin 2. This is the 75 ohm input for NTSC video. If the wire is missing, you'll need to solder a wire from the center of the plug to pin 1.

The output. Here's where I got massively confused. I'm including a picture that shows exactly which wire goes where. Basically, pin 1 (the pin closest to the composite input) is ground, pin 2 is vertical sync, pin 3 is horizontal sync, pin 4 is red, pin 5 is green, pin 6 is blue. The inputs on your G07 are standard for an arcade monitor, but just to overclarify, the inputs from left to right (if you're staring at the open back of the cabinet) are horizontal sync, vertical sync, ground, blue, green, red. Ridiculous I know. I'm also including pieces from the G07 manual, as well as the decoder board's manual so you can clearly see where everything goes.

The controls. Regardless of what has been posted elsewhere, you SHOULD fiddle with the controls to get your picture just right. And no you don't need a scope or any other fancy technical equipment. Here's your step-by-step process:

1. Hook your G07 up to either another game that has a test screen, or something that can generate one. Get the controls set on your G07 first. While you can do this step after you've setup your decoder board, I still recommend setting your monitor first.
2. Write down where the setting are at when you start so you can go back if mess something up too bad.
3. Start with the contrast (R106) and sub-contrast (R107) controls (see the manual pic for details). Get that right first.
4. Adjust the brightness (R130) so you're getting as nice a picture as possible.
5. Adjust the color (R139) so that the picture looks colorful, but not washed out and over-saturated.
6. The tint (R136) should be close to the middle, but if your color drive is off on your monitor, you may need to lean one way or another.
7. Chroma input shouldn't matter much but you can play with it to get the best possible picture.

And that's about it. If you're not getting a picture, check to make sure no resistors are blown from someone plugging it in wrong->replace the caps->check transistors (you can Google it if you don't know how to do this)->replace the IC chip if you're still having problems. After that, I'm not sure what to say but perhaps someone else can pipe in here on what to do.

Some may disagree with what I've posted here, but since practically nothing is written out there (at worst), though some things can be found if you spend hours Googling about the board (at best), I figured I'd share what has worked for me. Some pictures are posted here, and some on the next reply of this thread.

Good luck and happy slaying.
 

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Thought it might be a good idea to link to this thread from here as well. The additional information from @alggamer on resistor 128 was very helpful to me when determining how best to power my board both in testing and once I eventually get it all installed in the cabinet. I chose to use an external 16V power adapter ($14.95 off Amazon) to avoid having to mess with soldering on the monitor PCB (not using a G07 so would have to determine best place to draw power to the decoder) and/or having to remove R128 and solder in a jumper on the NTSC board if using a 12V power source.
 
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More info and a few pics of the 'does it just work' test I did. No monitor or NTSC board adjustments at this point.

I cut the end off the 16V adapter wire, determined the hot lead with a multi-meter, then connected that to pin 1 on P102 and the ground to pin 2 on P101. For the connections from P103, I followed the pin out in the NTSC decoder board manual posted above and ran those to the corresponding pins on the monitor.


20231101-131712.jpg20231101-131745-001.jpg
 
Thought it might be a good idea to link to this thread from here as well. The additional information from @alggamer on resistor 128 was very helpful to me when determining how best to power my board both in testing and once I eventually get it all installed in the cabinet. I chose to use an external 16V power adapter ($14.95 off Amazon) to avoid having to mess with soldering on the monitor PCB (not using a G07 so would have to determine best place to draw power to the decoder) and/or having to remove R128 and solder in a jumper on the NTSC board if using a 12V power source.
Just an update on this. Turns out using the external power adapter resulted in some noise in the picture. These lines were not originally present in my testing, but materialized over time. When I switched over and jumped off a 15V trace off the CRT, the lines went away.

lines.jpeg
 
The noise could be a result from using a stand alone adaptor. Those are usually not the best at filtering out line "noise". If you're using a switching power supply, the 12vdc off of them is clean and smooth enough to operate the card with the R128 jumper in place. Nice work all around.
 
This takes me back. When I first got my Dragon's Lair it did not appear to have ever really been worked on since leaving the factory. My theory is that the player died and it was put in storage.

The only issue I had with it when I brought it home was that during certain scenes I would get a vertical roll. Any bright flash caused the monitor to lose sync. I was able to correct that problem by making adjustments to the monitor and the decoder board (also have the NCST board recapped).

I used a video test laser disc called "Video Essentials" to set up the monitor and it worked very well.

Here's my thread (circa 2014).
 
Wanted to add a note here that 1kGen mentions jumping off W406 from the G07 in the opening post. It should be W403 as noted at the bottom of the NTSC board documentation shown. If you jump off W406, the monitor will go into high voltage shutdown....ask me how I know 😂
 
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