Problems when extending cart. connector

vomitsaw · Post by **vomitsaw** » Sun Jul 15, 2007 5:18 pm

As I'm sure many of you already know, re-wiring a 72-pin NES connector off-board is the exact opposite of fun. Discovering there's a problem afterwards is... upsetting, to say the very least. This is the point I'm at now, and I come to you with a good question that I hope can be answered. But first, I'll give a little recap of what I've done so far and what I'm trying to do.

I've ripped the unnecessary crap off the NES board (mystery expansion port and RF modulator), and installed the 7805/4401 video amp directly on the board. That's all fine and dandy and has nothing to do with the problem I'm having. Basically, I just need to extend the cartridge connector well off the board to accommodate a case design which I haven't entirely fleshed out yet. (I'm allowing myself plenty of room to move/twist the cart. connector around). I've wired it to the board using two pieces of hacked-up IDE ribbon cable measuring about a foot or so.

Upon testing it, some games worked fine (Castlevania 3) and others did not (Tengen Tetris), resulting in random artifacts appearing on screen. I thought at first that maybe the games were dirty. Cleaned em, same problem. The connector also gets a damn good grip on the games, to the point where I can literally lift the game up in the air and wiggle it to my heart's content without it freezing up. Checked continuity on every line and it's fine. (No crossed/disconnected wires). The problem persisted. Tested the problem games in other working NES systems and they worked perfectly, first try.

So now I'm thinking I've screwed up something on the board. Wanting to isolate the problem, I decided to test the board with a regular connector. With a tear in my eye, I de-solder all 72 wires from the board and install a regular NES cart connector... the games work fine. SO... now it's obvious that the problem has something to do with my extended connector.

...

BUT WHAT? The continuity was fine! So I guess what I'm asking is... when extending the cart. connector off the NES board, is there a limit to the length of cable being used before signals start "petering off", so to speak?

Any input would be greatly appreciated, as I'm done fresh outta' ideas!

jeroen · Post by **jeroen** » Sun Jul 15, 2007 11:37 pm

Cold soldering joint?

jedi knight · Post by **jedi knight** » Sun Jul 15, 2007 11:51 pm

Is there a problem with the cart slot itself?

vomitsaw · Post by **vomitsaw** » Mon Jul 16, 2007 5:05 pm

jeroen wrote:Cold soldering joint?

Perhaps. There are a few spots on the connector end of the cable where my workmanship got a little sloppy, but still, continuity appears good all the way down. May end up redoing it anyway.

jedi knight wrote:Is there a problem with the cart slot itself?

Nope. Since I made that last post, I soldered the cart connector directly to the NES board and the games in question loaded perfectly. Hell, better than perfect. (It's almost SCARY good). So, I ended up cutting a few more inches off the cable, reattached the connector to the other end, and the same exact problem is showing up. So, there's obviously something wrong between the board and the connector. Something else occurred to me late last night though. That excess cabling may be pushing my dinky DC adapter beyond it's limits. Gonna try something a bit stronger and see if it makes any difference.

vomitsaw · Post by **vomitsaw** » Mon Jul 16, 2007 7:18 pm

Okay. So, I've swapped out the crap DC adapter for a 12V 1A adapter (which should be more than enough juice to power this stupid thing) and I'm still having the same problem. However, I notice now that the graphical glitches aren't immediately present, but appear shortly after powering it up. (Usually less than a minute). The plot thickens. I've been hacking apart Nintendos for years and I've never run into this problem. Baffling.

Rekarp · Post by **Rekarp** » Mon Jul 16, 2007 7:42 pm

Try new wire. There might be a kink/break in the wires your are using.

Kenny_McCormic · Post by **Kenny_McCormic** » Mon Jul 16, 2007 11:42 pm

signal loss from too long of a wire?

Felino · Post by **Felino** » Tue Jul 17, 2007 2:33 am

Sounds power related to me.

vomitsaw · Post by **vomitsaw** » Tue Jul 17, 2007 4:44 pm

Rekarp wrote:Try new wire. There might be a kink/break in the wires your are using.

I'll try that next. Thinking of using some of that 80-conductor UDMA100 ribbon cable. Really small. Hope that won't cause any problems.

Kenny_McCormic wrote:signal loss from too long of a wire?

That's exactly what I'm thinking right now. I've extended the 72-pin connector off the board before without any problems, but never quite this far. I'm a little worried of cutting it back too short though, because I'm not exactly sure how much play room I need. All that depends on the case design, which I haven't nailed down just yet.

Felino wrote:Sounds power related to me.

I thought that too. At first, I was using a crap little 300mA DC adapter, which worked just fine BEFORE I added the ribbon cable. Figured that maybe the extra wire was drawing too much juice. I've since switched to a 1000mA adapter, and even tried a 3000mA power supply. The problem is still there.

I've got a few more things to try, but right now I'm putting my money on cable length and signal loss. Has anyone else had similar issues?

Rekarp · Post by **Rekarp** » Tue Jul 17, 2007 7:29 pm

It could be signal loss but I seriously doubt it. If I was you I would go up in gauge size. I used thick ribbon cable for my SNES cart relocation and it worked fine. (worked first time to boot

)

vomitsaw · Post by **vomitsaw** » Thu Jul 19, 2007 12:54 am

Rekarp wrote:It could be signal loss but I seriously doubt it. If I was you I would go up in gauge size. I used thick ribbon cable for my SNES cart relocation and it worked fine. (worked first time to boot )

...Thicker than standard floppy ribbon cable? I've been using this same stuff for a while without problems. Until now, that is. I'll probably end up trying different cable anyway though. I don't have many ideas left at this point other than holy water and/or goats blood.

Here's a few images of what I'm working with:

jeroen · Post by **jeroen** » Fri Jul 20, 2007 11:38 am

you made an intire pcb for it?

vomitsaw · Post by **vomitsaw** » Fri Jul 20, 2007 5:48 pm

jeroen wrote:you made an intire pcb for it?

Yep. I got tired of using that RadioHut perf board crap . And it's size doesn't matter much because this particular project isn't intended to be portable. (In case you were wondering).

Unfortunately, I'll have to take a break from working on things 'till early next week. The roommate is hogging up the "work area" with all her art crap right now, and I'll be out of town anyway. This problem is gonna bug me all weekend.

jeroen · Post by **jeroen** » Fri Jul 20, 2007 6:19 pm

possible the pcb has a broken trace?

vomitsaw · Post by **vomitsaw** » Mon Jul 23, 2007 11:47 am

jeroen wrote:possible the pcb has a broken trace?

Nah, I checked all the continuity from the connector pins to the other end of the cable. Everything seemed fine. However, I'm not ruling my pcb out just yet. Some of the traces ARE a little thin in spots. (Probably etched it a bit too long). Anyway, I should be returning home today, and hopefully be able to continue investigating this problem. It's driving me nuts.