Turtles PCB issue

[IPD]

Decided to dig up my old Konami Teenage Mutant Ninja Turtles PCB today and play some games. Haven't started it in a long time, but I've never had any problems with it in the past.

Plugged it into one of my NACs, double checked everything as usual, and it starts up fine. After 5 seconds I smell something burning, and I see smoke coming from the PCB. Looks like the Konami 051550 custom is busted. Oh great. It's been a while since one of my PCBs failed me. Anyway, looking at the component I don't see any obvious burn marks on or around it.

So I hook it up to a supergun on the workbench, and it starts up fine. I run it for 15 minutes, no smoke. No problems whatsoever.

Back in the arcade room, I hook it up to another cab, NNC this time. And it runs just fine. I play the first levels. Working like it should.

OK, so I connect it to the NAC again. Starts up fine, 5V is at 4.97. Runs fine, but I see smoke again after 5 seconds. It's definitely coming from the Konami 051550 custom. So I turn it off again. Weird. I try it a few more times with a supergun, but it works just fine, like before.

Is the NAC busted somehow? I play on it all the time. It's been a dedicated MVS cab for a long time, so during the evening I played a few MVS games, but I also tried the CPS1 Multi and a couple of CPS2 games. No problems. So the NAC seems fine after all.

Dunno what to do here - any advice?

 

[ekorz]

Dunno what to do here - any advice?

Yeah don’t play it on the NAC!!

But in all seriousness that custom handles reset signal and coin counting. Reset is independent of the cab. Coin isn’t.

https://www.jammarcade.net/konami-051550-reproduction/

So things to try? Not exactly sure but if I had to guess something is short on the pcb/051550-custom in a way that the supergun and the NNC don’t interact with, but the NAC does. Superguns don’t have coin counters… does the NNC? Does the NAC have two? What if you disconnect the coin counter(s) on the NAC?

 

[twistedsymphony]

that custom handles reset signal and coin counting.

I'd put money on the coin meter circuit being screwy
looking at the NAC circuit diagram: https://github.com/Softdrink117/new-astro-city-ground-wiring/blob/main/Wiring_Diagram_Full.png

There are 4 wires going to the coin meter. 2x grounds 1x 5V and the last wire goes to the coin meter (pin on the JAMMA edge...
that pin should be an output pulse from the PCB to tell the coin meter to increase, but if the meter is bad or shorted it could be feeding back into the PCB and cooking your custom.

Just speculation and something to investigate.

with the cab off check resistance between pin 8 on the JAMMA connector and ground and Pin 8 on the JAMMA connector and 5V... see how that differs from the NAC and the NNC and super gun.

 

[IPD]

Thank you for the help. I did some more investigation yesterday, just a few simple things based on your replies.

- Checked the coin counter on the NAC and it works with every single game I tried.

- Checked the coin counter on the NNC. It works. Both with Turtles and with other games.

- Then I disconnected the coin counter on the NAC and tried again with Turtles. Game runs fine. No smoke. Good to know.

At this point I was going to grab my multimeter and do some testing based on @twistedsymphony's suggestions .....but I have several NACs. Let's try the turtles PCB in one of the other NACs first. So first up, NAC#2......and smoke again! Interesting. Let's try it with NAC#3, and yes - smoke again. Poor PCB.

So my Turtles obviously doesn't like any of my NACs. The Konami custom gets fried every time.

I'm definitely no expert, but suspect the problem is the PCB itself and not the cabs. I'm tempted to order a new repro custom from Caius and do some testing with that. What do you think?

 

[ekorz]

I think when the pcb is plugged into a NAC you’ll get smoke because the two together create a short circuit. The question is if the custom is like that normally, in which case a repro will do the same thing. Grab the multimeter!

 

[twistedsymphony]

I have several NACs. Let's try the turtles PCB in one of the other NACs first. So first up, NAC#2......and smoke again! Interesting. Let's try it with NAC#3, and yes - smoke again. Poor PCB.

To further what ekorz said... it seems like there's nothing "wrong" with your NAC or with the PCB, but something with how the NAC is designed is incompatible with how the Konami PCB is designed.

I would recommend against too much more testing here as you can absolutely burn out the chip beyond repair, it's also possible you've already created damage that has shortened it's lifespan.

 

[ekorz]

What revision are you playing? If it’s the 2player roms you can disable the 2nd coin input with a dip switch setting.
(if it's not the 2 player roms... are you trying to run 4 coin chutes and maybe that's the problem?)

SW1 00001111 says mame

 

[twistedsymphony]

according to the NAC wiring diagram 2P coin isn't even wired up. NAC doesn't seem to use coin lock outs either

another thing you can do is place a piece of tape over pin 8 on your JAMMA edge to "disconnect" that pin. I'd still test that pin with a multimeter compared to the NNC before I plugged it back in though.

if it's not the coin meter then my next likely culprit would be the speaker connection, if the cab is grounding the Speaker - that can cause a short for PCBs that use floating speaker outputs. easy enough to unplug the speaker connection from the JAMMA harness on the NAC to test that. or just use a multimeter to check if the speaker - on the NAC is floating or grounded.

 

[IPD]

another thing you can do is place a piece of tape over pin 8 on your JAMMA edge to "disconnect" that pin. I'd still test that pin with a multimeter compared to the NNC before I plugged it back in though.

if it's not the coin meter then my next likely culprit would be the speaker connection, if the cab is grounding the Speaker - that can cause a short for PCBs that use floating speaker outputs. easy enough to unplug the speaker connection from the JAMMA harness on the NAC to test that. or just use a multimeter to check if the speaker - on the NAC is floating or grounded.

Well, we can probably rule out the speaker connection - if I disconnect the 4 wires going to the coin counter on the NAC and plug in my PCB I get a working game without any smoke.

I checked resistance on pin 8 to GND and pin 8 to 5v with a multimeter on the NAC, and moved over to the NNC and noticed:

Pin 8 isn't connected on the NNC...

That didn't cross my mind to check yesterday, because the coin counter on the NNC works.

Looking at all my cabs, this NNC is the only one without pin 8 connected on the jamma edge. I bet that if I for example plug in the PCB in one of the Egrets I'll get smoke as well. But I'd rather not try that.

 

[IPD]

Small update.

I forgot all about this, until a few days ago when I bought a bunch of PCBs locally and one of them was another Turtles board!

I hooked up the new Turtles board to one of the NACs, and guess what - it works. No smoke from the 051550. I left it running for ~10 minutes or so but it played just fine.

At least I now know the real problem is the old Turtles board, and not the NACs.