Tron nvram m48z02 problem

TheShanMan

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I've been trying to get my battery backed ram working in my Tron without luck. Installed it without any mods and I found that the game would randomly reset (switching back to 6116 worked fine). I then played around with tying vbatt to +5v - both before and after the inline resistor. In both cases I either get RAM B02 error or garbage. Now if I try just the nvram alone I'm still getting garbage so I'm not sure if it's now bad for some reason or if it's just temperamental, whether it boots ok and resets later or boots to garbage.

Any ideas what I'm doing wrong or if my chip is bad? I'm currently back to the 6116 and everything's working fine, so no other issues in the system.
 
I really wish I could help you... I had a stack of those chips that I was selling for a while until I started getting messages back that people were having trouble with them. The one I've put in my Tron machine has been working flawlessly for about SEVERAL months now, and I just put another one in a friends new Tron machine, and it's working like a charm too. Neither PS board has a battery on it... all that was required was tweaking the +5 a little bit on my machine because it was a smidge too low.

But most people were getting the same thing you were, garbage and RAM errors on boot. I tested every chip in my machine several times before I sent them out, and they all worked perfectly in my machine... so there must be something different about the setups... no idea what could be so different that it would cause the chips to not work... but there MUST be something. Since I couldn't figure out the issues, I stopped selling the chips... which sucks because they were actually selling pretty good. :(

InstallTest.jpg
 
To your knowledge did everyone that had the problem just give up and use a battery of some sort? Or is anyone actively trying to figure out how to solve the problem? I'm thinking of maybe going the phone battery route, but I'd REALLY rather get this to work. I'm certainly willing to try different stuff to get it working. Just not sure what that would be.

Have you ever heard of the chip causing the game to reset? Or just the boot problems. I was getting the resetting the first time I put it in. I played a game up to about 50,000 and right in the middle of game play it just reset, and reset several times after that as well. RAM errors at boot up make perfect sense to me if the chip isn't quite right for whatever reason, but I don't understand why a different RAM chip would cause the processor to reset.
 
Timing glitches in the circuit... Things just aren't quite what the newer chip expects.

If you get timing signals that are incorrect then you might just be seeing spurious data on the bus.
 
How would you explain it working for apparently quite a few people? Tolerance type differences? I don't suppose you could think of any other possible replacement chips?
 
I do believe I was getting reset errors at first... But I turned the voltage up a little and everything settled out... check the voltage at the pin that is highlighted in the picture I put up about. If you're getting 5VDC at the PS, you might only be getting 4.5 or less at the chip itself, where it counts.
 
Sorry Scucci, I misinterpreted your 5v suggestion as something that was actually unrelated to the chip swap. I'll give that a try for sure. Looks like VR102 is the pot to adjust?
 
Yeah, either VR102, or the other one. lol

Sorry, I really can't remember off the top of my head. I adjust mine with the machine on, and I know that when I touch the 12V pot, the speakers hum... but sadly I can't remember off the top of my head which is which. I skimmed the manuals real quick and I didn't see it talking about which is which.

I guess you could, for safety's sake, just unplug the boards and the amp and shove the neg lead of your DMM into the yellow/black wire on the PS, and the pos lead into the the socket for a +5V "red" (according to the manaul, they're blue on my machine) wire and try one then the other... then probably mark them if your memory is as bad as mine is...
 
You guys are awesome. Even though my tron has been working flawlessly since I got it last Dec, the +5 was only 4.7 at the PS board! I raised it to 5.0 and now with the m48z02 the game boots fine and I experience no resetting. And that's without eliminating the vbatt diode!

Thanks!
 
Yeah, we're pretty awesome... I know, I know... lol

Glad you got it working, finally someone else was able to get the NVRAM working. The one in my machine at the arcade does NOT like the crappy power the mall is supply'ng, esp. when you hit the breakers in the morning. But, after a quick reset she runs just fine. Minus the scores getting reset every week or so (because of the goofy power at the mall), she runs like a champ. Had ZERO problems with the machine at home, so you'll probably be just fine now. ... Well, for the next 10-15 years or so when you have to replace the NVRAM again.
 
Was reading this thread to fix my own similar problem. I've only got 2.6v at the pin indicated in the picture above (though my chip is different, it's an MB8416-20 8133 H13...which I believe the datasheet says it should be 4.5-5.5v).

However, I've got 5v on the board at all the other chips I've measured.

What might cause this? A bad chip? Bad socket? Something else?
 
Okay, more info.

Seems like my battery is dead. Also the reset line had been cut when I got it.

I had read about hooking 5v to the v batt, and since the reset line gives me 5.5v, I figured that should work. But if I hook that onto v batt (pin 16 on J1 on the board) and then test the pin, I only get 3v. Huh?
 
Okay, even more info. The line coming into the harness for v batt is actually okay...5.5v. The line coming out of the harness is 5.5v also. The pin is 4.7v though.

I've done it with a direct wire too (not using the harness connector). Attaching a 5.5v wire to the pin...only puts 4.7v on the pin. What could be happening?

As a result, the CMOS has low voltage, as do 2 other nearby chips at F1 and F2 (a 14053B 8205, and a 14017B 8205 respectively).
 
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