Nes (72-pin) to Famicom (60-pin) converter mod

[Barawer]

Hmm, i checked on my Famicom AV Bubble Bobble and Castlevania 3 (both US and JAP versions) and they worked fined, played for 10+ minutes without a problem.
That's why i think that the problem originates from the original Famicom, will have to do some testing for that though.

[GadgetUK]

Test SMB2 & 3 as well - those were glitching as well, resets and lockups.

[immrbig]

I am using a Famicom AV.

[Barawer]

Tested SMB2&3 - 2 would freeze up in seconds, 3 works fine. Tested in my frontloader, the rom itself is fine..
Did you manage to find some sort of fix for it?
I was told in the past by Bob from RetroRGB that he heard that someone is making an adapter that has everything fixed, maybe we should just wait..

[GadgetUK]

Yes, you've described the issues I had with SMB2!   That's good news!!  I did another fix last week that I finally posted today:-

https://www.youtube.com/watch?v=mOFHj3Bw9Bc

[Barawer]

Wow great job! Would you recommend adding the copper plate or adding a resistor?

[GadgetUK]

I would start with the Copper tape - it's much less destructive to the board, easier to do and will very likely fix the problem without needing that resistor.

[Barawer]

Great! ordered some right now. Will check it out once it gets here and let you know if everything works.
Again, thank you for researching it and finding a solution, once i see how it works for me i will update the guide.

[thecavalry]

Copper tape definitely made the adapter infinitely less glitchy for me. I couldn't get the solder to flow over to where i scratched off the coating. I ended up just running a wire to ground from my solder bead. I have not added the additional capacitor/resistor.

I tested with the Everdrive N8 loading bubble bobble for about 10 minutes without any resets. I also tested with the super mario adventure romhack (which i would get crashes on regularly) and found no issues in the few minutes I spent with it.

I also confirmed it works with SMB2 cart without issues, though I hadn't tested prior to adding the tape. However, I can't seem to get my Metroid cart to work with the adapter. The game itself runs fine from my everdrive, but my cart doesn't seem to want to do anything but hold on the grey screen.

[GadgetUK]

Make sure you smooth the ripples out of the tape as well - just rub over it with tissue or something to flatten it and remove ripples.  Strange that you've still got a problem with Metroid, maybe the 100ohm resistor on the M2 line (and isolation of the existing M2 trace) is required after all.  I cannot get mine to glitch at all now and Metroid works fine for me.  With regards to not being able to solder onto the scratched off ground trace - it sounds like you need some flux!   Thanks for testing!  I've heard from a friend that his is working perfectly also, so it's looking promising!

[thecavalry]

Not needed in this case. I went and gave it a thorough cleaning with a bit of an abrasive cleaner to make sure corrosion wasn't the culprit. (It was particularly dirty from an ebay seller - and I had gotten it to work on my front loader NES with just alcohol/q-tips)

My Metroid cart is completely clean now, and fired right up without any troubles through the adapter. So, it seems the copper tape shield is the magic solution after all.

[GadgetUK]

That's awesome news!!!  Thanks for posting!  =D

[Barawer]

That's great news! I wish mine would arrive already.
I want to make sure, where did you solder the copper to? on nesdev it seems that pin 1 and 72 are the ground ones. Am i correct?

[GadgetUK]

Yes, ground is pin 1 or pin 72 on the 72 pin connector!

[immrbig]

Copper tape, in combination with the 100 ohm resistor AND a capacitor (I used a 47 pF ceramic cap, because that's what I have on hand)  seemed to have fixed my NES ED N8 crashes on my Famicom AV.

However, I was getting some noise in my picture because of insufficient grounding for the copper tape. In addition to the via in the video, I also grounded the tape to pin 72 on the NES side and pin 16 on the Famicom side. I only noticed marginal improvement after grounding to the Famicom side, but grounding the tape to pin 72 on the NES side made a big difference.