MKL audio mod PCB

Neo Geo MV1FZS 5V and Stereo Mod

When I finally fixed my consolized MV1FZS last month and was able to play some games again, I notized that it outputs mono sound only. It is now time to make some some additional modifications to it.

5V Mod

MVS boards need both 5V and 12V voltages, and 12V is used for the audio amp only. As I’m going to add a new stereo audio circuit, there is no need for the 12V feed anymore. This consolized MVS draws the 12V from the now obsolete XL6009E1 DC-DC converter:

XL6009E1 DC-DC converter
XL6009E1 DC-DC converter

Once again mmmonkey provides a good resource for the modification tutorials. I need to remove 4 components and change some traces. For full details, please read the tutorial ‘MV-1FZ 5V Only Mod’.

12V amp area
12V amp area
12V amp area
12V amp area

Stereo Mod

Once I was done, I was finally able to begin with the stereo modification. In order to achieve this, 3 audio signals need to be tapped at the marked solder points, but first the connection between left and right audio channels needed to be broken by removing the two SMD resistors (1 and 2). Again, please read the tutorial ‘MV-1FZ Stereo Mod’ for details.

Tap audio signals
Tap audio signals

I went for the more sophisticated stereo splitter and amp by MKL. There is also a SMD variant, but I didn’t have the time to order and build the PCB for it. Instead I designed a perfboard for the components I had available. Pay attention to the NPN transistor, as I had to use a BC546 instead of a 2SC1815 and had to rotate it accordingly. I don’t like the 5V connection across the PCB, so if I ever have to do that again, I will probably rotate the transistors by 180° and have the VCC rail in the center of the PCB.

MKL audio mod PCB - front
MKL audio mod PCB – front
MKL audio mod PCB - back
MKL audio mod PCB – back
MKL audio mod PCB - front
MKL audio mod PCB – front
MKL audio mod PCB - back
MKL audio mod PCB – back

A shielded cable connects the 3 signals to the mixing PCB, I glued it in place were the DC-DC converter was before.

Tap audio signals
Tap audio signals
MKL audio mod PCB
MKL audio mod PCB

After I connected the separate audio channels to the SCART socket, and play-tested it for a couple of hours, I finally removed the electrical tape and secured all sensitive areas with Kapton tape:

PCB protected with Kapton tape
PCB protected with Kapton tape

In the meantime, Universe BIOS v4.0 has been released, so I took the opportunity to upgrade this board to the free version v3.3.

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