NES VRC6 mod with CV3/Akumajou Densetsu cart

Gyromite

Gyromite

So this all started with reading about how gyromites occasionally containing famicom converters. Due to early supply constraints during the NA release, the first run of gyromite carts all contained these funky little adaptor, which allowed them to resell famicom gyromite in the US. So I tracked down my gryomite cart, felt it was clearly super heavy and cracked it open.

Gyromite, disconnected from the FC converter

Gyromite, disconnected from the FC converter

The inside of Gyromite, with FC converter

The inside of Gyromite, with FC converter

A converter! Hooray! So immediately I decided I wanted to make my self an Akumajou Densetsu cart. CV3 is my favorite castlevania, and I much prefer the Japanese version to the US version (mostly due to the music, but also because I hate level based damage scaling). So I went and google and found this cute mod. Now I REALLY needed to make that cart. So I ordered an Akumajou Densetsu famicom cart and began planning out the rest of the mod. I didn’t wanna do the wire-out-of-cart mod — that’s cute but kinda ugly. So I began researching how I’d do the console mod. Turns out there are like a million small variations on how to do this, so that took me forever to work out.
Also had to take the time to do my version of the cover. Callan’s nice looking and was the basis for mine, but certain elements, like weirdly cropped art and the logo didn’t work for me. Since there was no good scans of the CV3 splash art, I had to sorta rebuild the logo. In the end, I did the label with photo paper and some glue. Worked much better than the ‘label’ method. Label method gets the label thickness right, but lacks the clarity of a nice print.

Akumajou Densetsu with my custom logo

Akumajou Densetsu with my custom logo

I cannot explain how much hell this was to get out of that fucking case

I cannot explain how much hell this was to get out of that fucking case

Anyways eventually I got all my components and decided my course of action. One source of confusion for this mod was the resistors. Resistors are required to balance the audio of the VRC6 with the NES, else the VRC instruments will overpower everything. Most recommend 47k resistors, but other recommendations, especially with famicom carts, went up to 100k resistors. So instead I just got a 100k pot. There were also several different unused pins you could use on the nes for this mod and I decided to use the same one as the powerpak. I doubt I’ll be buying a 120$ powerpak any time soon, but hey, best to be careful. Then I could also adjust the volume accordingly.

The annoying thing with the powerpak pin is it required me to wrap a wire around the converter. It also sucked because that pin was harder to solder without interfering with the contacts. Worked out fine in the end. The internal mod on the NES was much simplier. The NES has extended audio capables, but they were only made to work through the expansion port on the bottom of the NES. Soldering the pot between expansion port 9 (the expansion music min) and port 3 (audio out) was all that was needed to get the mod working. The pins didn’t take solder well, so it was a bit of a pain, but working on those pins felt less risky, so it wasn’t that big a deal.

Connecting to pin 54 on the other side

Connecting to pin 54 on the other side

Connecting to pin 45

Connecting to pin 45

Pin 3 and Pin 9, with the pot through the front. Just need a nice dial now.

Pin 3 and Pin 9, with the pot through the front. Just need a nice dial now.


Anyways here’s a little peak at the mod. Sorry for the poor quality and rotated video. I’ll probably stream the game tomorrow.

4 thoughts on “NES VRC6 mod with CV3/Akumajou Densetsu cart

  1. That is just plain rad. I’m curious now though how much the whole thing set you back, next to the cost of just finding yourself a famicom, maybe get in on the experience of shouting a Pols Voice to death sometime.

  2. I spent 40 bucks on Akumajou Densetsu and 3 dollars for the potentiometer. The gyromite adaptor is worth like 20 bucks, but I had that already and I could find one for like 2 or 3 dollars. A famicom is about 60 bucks, but I’d still need the game. a FDS would be fun at least though because I could do whatever with it since it’s apparently easy to copy games?

    Still, the mod it’s self cost barely anything but time and I love an excuse to play with my soldering iron anyways.

  3. I can’t attest to the label (wow, great work), but I can offer a little advice on getting a cheap adapter:

    1) They’re heavier
    2) They have 5 screw backs – not 3
    3) The pins are different – they are not symmetrical.

    And only look for the following games to save time:

    1942
    Clu Clu Land
    Donkey Kong Jr.
    Duck Hunt
    Elevator Action
    Excitebike
    Golf
    Gumshoe
    Gyromite
    Hogan’s Alley
    Mike Tyson’s Punch-Out!!
    Pinball
    Raid on Bungeling Bay
    Rygar
    Soccer
    Stack Up
    Tennis
    Urban Champion
    Wizards and Warriors
    Wrecking Crew

    Mind you, a lot of these titles would cost you more than the $20 asking price on ebay, but I’m not sure those adapters will work the same in the console (pretty sure they stick way out of the console).

  4. Oh sweet, I’ll check my Golfs, Duck Hunts and Soccer carts tomorrow. Have duplicates of a few of those (dad loved garage sales back in the day) so I might get lucky. Dunno what else I might important (JP Ninja Gaiden 3 maybe?) but it’s good to have options!

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