Repairing a NES controller - Select and B seem fused?

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RetroProf
Posts: 8
Joined: Thu May 11, 2023 2:27 am

Repairing a NES controller - Select and B seem fused?

Post by RetroProf »

I had a working NES controller, and I bought a junk Famicom controller, so as to place the NES controller PCB inside the FC shell. They are identical. The junk FC controller obviously had no control plug, since it was hardwired inside the FC originally.

One problem: the "M bend" of the cables inside the controller are in different places, since on the NES the cable comes out the top, and the FC out the left side.

I swapped the PCB and it worked fine for a bit, but now has developed a nasty glitch:

Pushing either Select Button, or B button, activates the following buttons at the same time:
Select
Start
B

Pushing Start by itself works normally (I think).

I've tested this using Snake's Revenge since each button has its own unique function.

Theory: I moved the M bend around quite a lot, trying to untwist it, and I think I've broken the wires inside at that junction. It was pretty stiff and this plastic rubber is brittle after 40 years.

Or could it be a problem with the PCB control chip?

I tried cleaning the NES controller PCB but this did nothing. It's very clean anyway.

I cannot work out why it's only the Select and B buttons, why they activate Start, and why Start by itself works just fine.

Any ideas on how to fix this?

I have since put a different NES controller in the FC shell, being more careful with the M bend, and it works fine.

So I now have:
1x broken NES controller PCB
1x FC controller PCB (untested)
2x NES controller shells

I popped the plug on the NES pad using two pliers at the same time to push in the little nibs and slide it out. I was hoping that maybe I could just plug the FC's cable into it, but I discovered that the 5 wires are connected differently. On the FC the cable end has a little square block with 5 rows of double teeth pins. On the NES the cable end connects to 5 long rods which are held in place.

In a worst case scenario, if the NES cable is at fault (because I broke the wires inside), I could cut the FC cable, and attach each of the 5 wires to the corresponding 5 rods in the NES plug (thus using the FC PCB and FC cable, and only the NES plug at the end).

But what if it's not the cable at fault?

I have a basic voltage tester and a box full of electronics tools and soldering iron.

Can anyone help me solve the mystery of why this controller is broken? Or suggest repairs I can attempt?

I could just buy another one for £15, but I like the idea of repairing stuff.
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