Electronics things are so fun. It’s like a little treasure hunt trying to figure out exactly how to hook them up right so you don’t blow them up. Electronics wizzes even have a special name for “blowing stuff up”, it’s called “letting the Magic Smoke out”. (The first time you hear one of them say this, you’ll marvel at how clever this person is. After you hear lots of them say it, well, you’re now part of the club. Well. At least they won’t throw you out of the club right away.)
So back to my story. I got a Vicor DC-DC converter that a buddy found on eBay. It came in a box. 
It looks like this. (The smaller one.) That was it… god forbid it should be labeled with where the wires go, or come with a little sheet. What fun would that be? So, a little trick I learned from somebody in the club, Mr Wizard himself, actually, is to look for markings that are model numbers and see what I can find. This is marked with ” VI-J41-CY-B1″. I figure the VI is Vicor, so I search for various combinations of those numbers and get nothing.
Long story short, I go to the Vicor site and find the page for the VI-200 and VI-J00 series products, (There are no products actually named VI-J00, that’s the class of product, and the specs are built into the name, see? What fun would it be if they actually told you the product name?) …and find this sheet. It’s the mechanical drawing for the unit, and shows this diagram with the explanation of where you hook up the wires.
Just click on this one, it will get bigger so you can see.
This is called the “pinout”, or, “where you connect the wires to make it work diagram”. See what you’ve learned? You can now be at a party talking to an Electrical Engineer and take a deep sigh, and say, “Damn, man, I was hooking up the Vicor VI-J41-CY-B1 yo (that J31 is such a piece of crap ain’t it? Nothing like the J41 with the BusMod and the heat sink option, unless of course you’re talking the HAM version…*) and damn near let the Magic Smoke out when my dog ate the pinout… ” then dash to the bar to refresh your drink. Except if he’s an EE, he’s probably at the bar. And won’t leave. (If you happen to notice a hot woman you know, are friends with, can talk to or even have “relations” with, do not, under any circumstances go talk to her if you want to remain “in the club”.)
Here’s the cool part of the treasure hunt, though. This is what they show on the site for a product shot of what I have. 
Doesn’t look anything like what I have. I’m a photographer, I know these things. It’s actually a clever disguise to make the treasure hunt more fun. It turns out, the unit I got has the BusMod unit attached, basically so you don’t need to solder connections to it and can just screw mount them. Here’s what the site says, it’s awesomely Wizardly.
* “Rugged chassis-mount housing for VI-J00 module (add-B1 suffix to module number for preinstalled)” Not for use with HAM module.
Now wait. I would ONLY use the HAM module, since everything I run and I myself am totally HAM. Oh. OK. Whatever.
If you’re standing in a bar with no chance of being with a woman, and need some awesome geeky reading material, check out the complete technical resources for the Vicor VI-J41_CY-B1 here.
If you just want to slap it on your bike and get 12V from your 72V pack then connect the high voltage ground to pin 4 and positive to pin 1, and 12V output positive goes to pin 5 and 12V ground to pin 9.
Like this.
Yeah so one more thing nobody tells you anywhere, until of course you blow yours up and then everybody chimes in and says oh NOOOO don’t do it THAT way, I did it THAT way and blew up about 6 of them. The switch you put in on the high-voltage side? It should be on the positive. That is, the negative 72V always is connected, the positive is switched on and off. Because if you don’t it will let the Magic Smoke out.
Funny. The Vicor guy who commented below didn’t think to mention that either…
PS
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OK, if you want to actually look like you know what you’re doing, there are a couple of other things that this Vicor will do. I have to tell you, but I’m going to make it sound like I figured it out myself. What can I say, I have a supremely hot wife and can talk to women, I have to do everything I can to maintain my cover and stay in the club.
You can turn this thing on and off. Let’s say you want to leave it tied to the high voltage pack, always on, and want to turn the 12V on and off, like, say, parking lights or a radio or something. That’s what the “gate” pins are for. If you connect pin 2 to ground (pin 4) it will turn the unit off. If you use this, you need to put a 1 uF capacitor from 2 to 4 (gate in to -In). Otherwise the unit will shut down and won’t turn back on without being completely disconnected.
I have no idea why.
You can also “trim” the voltage. That means adjust the output voltage a little bit. +/- about 10%. Why you would do that, I wouldn’t know. (One of the dirty little secrets of electronic component design is that they can all operate within a voltage range. For example, anything rated 12V can probably do just fine between 9V and maybe as high as 18V. So if you need to adjust the trim, I suspect you already know how.)
Thanks to you-know-who-you-are. I won’t tell the rest of the club that you have a hot wife. I promise.
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