First question, do you have a multimeter?
If not, go buy a cheap one that can check for continuity, it’ll be the best tool a modder can get 
(I simply cannot recommend enough learning how to use a multimeter just to check for continuity)
If you don’t know how to use a multimeter to check for continuity, here’s a great tutorial that i used (given from toodles) and as a result, now, I can’t go without my multimeter when doing any form of modding.
Here’s my basic trouble shooting guide, when one board fails to load or no boards load (basically go down the imp’s 7 points you solder to):
[LIST]
[] Ensure the three boards are grounded. Do this by, having one probe on the ground point of the imp and use the other probe and touch the ground of the cthuhlu, then a ground on the madcatz, if you get a successful beep, then proceed to the next step if not, resolder your grounds.
[] Ensure the three boards are powered. Do this by, having one probe on the vcc point of the imp and use the other probe and touch the vcc of the cthuhlu, then the +5v on the madcatz, if you get a successful beep, then proceed to the next step if not, resolder your power points.
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Most of the time, that’s all thats necessary, however there’ll be your odd occasion when you get the “unrecognised usb device” chances are you’ve switched around your data points, placing the - in the + or vice versa. If that’s the case do the following:
[LIST]
[]Ensure the #2 + wire goes to the + wire on the second PCB that you want “activated”. Do this by, having one probe on the #2 + point of the imp and use the other probe and touch the + point of the second PCB you want activated, if you get a successful beep, then proceed to the next step if not, resolder your points.
[]Ensure the #2 - wire goes to the - wire on the second PCB that you want “activated”. Do this by, having one probe on the #2 - point of the imp and use the other probe and touch the - point of the second PCB you want activated, if you get a successful beep, then proceed to the next step if not, resolder your points.
[]Ensure the #1 + wire goes to the + wire on the first PCB that you want “activated”. Do this by, having one probe on the #1 + point of the imp and use the other probe and touch the + point of the first PCB you want activated, if you get a successful beep, then proceed to the next step if not, resolder your points.
[]Ensure the #1 - wire goes to the - wire on the first PCB that you want “activated”. Do this by, having one probe on the #1 - point of the imp and use the other probe and touch the - point of the first PCB you want activated, if you get a successful beep, then proceed to the next step if not, resolder your points.
[/LIST]
If those are all okay, and in you’re case the cthuhlu still won’t activate, then you will need to look at the way you’ve wired up the “guide” point on the imp
[LIST]
[*]Ensure the guide wire goes the point where its going to “switch” the pcbs (ie. bomberman has two versions of doing this, the original version was through the guide button, the new version is through the RS swtich). If you do the guide button way, make sure there’s continutity between the imp guide and the madcatz guide. Do this by, having one probe on the guide point of the imp and use the other probe and touch the guide of the Madcatz pcb, if you get a successful beep then you should have proper continuity, if not, resolder your guide point. If you’re doing it with the RS method, do the same thing as above, but make sure you’re soldering to the correct point.
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If all the above steps have been taken and none of your boards are loading, then check the USB connection on the IMP itself.
The above steps is the steps i’ve taken to troubleshoot ALL of my mods, and never have i needed to go beyond that, i’ve been able to see where i’ve gone wrong and points that “look” properly connected doesn’t necessarily mean there’s continuity through them.
What I highly recommend is checking for continuity between ALL boards and ALL solder points BEFORE installing the USB cable on the IMP. This way you know that all boards are connected properly and SHOULD work once you connect the USB cable.
That being said, if it still doesn’t work, then it’s beyond my scope and one of the more electric guru’s might be able to help you out.
I hope this little trouble shooting guide can help other people that has problems with this mod, I can safely say that I’m now approaching my 12th dual mod and I’ve learned a few things a long the way
