(Topic ID: 237326)

Help with Gottlieb System 80B MPU board booting

By Troyster42

5 years ago


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#1 5 years ago

Looking for some help here. I’m working on a Gottlieb Monte Carlo and I’m having problems with the MPU board. Before me there were a few things done to the board, a couple of resistors replaced, Q2-Q4 replaced, the first 2 sets of dip switches have been replaced. The piggyback board has been replaced with a Swemmer board. When I first got it the only thing that would happen when you turned on the power were some GI lights and for some reason the left flipper was working.

Since then I have recapped the AUX power supply, new trim pot on the PS along with new connectors. I did the ground mods in the cabinet along with the mods to the boards and the A1J4 connector. The game roms were bad as well and have been replaced.

I took the board out to bench test with Marcos test rom and I got 1 flash. Seemed to be the 5101 chip, I had a NVRAM all ready on its way. I put it in and the test ran fine, even the extended test. I put it back in the machine and it was working. Now the downward spiral begins. I stated to notice strange high score come across with odd characters for names, they were still the preprogrammed high scores. I then looked at book keeping and would see like 880 replays, 88 coins and so on a lot of “8”s when it should be a “0”. Then the memory check said the 5101 was bad. With how everything above was acting I thought so too. Then I started to have the MPU lock up, the scores would freeze and I would have to turn the machine off and on. It would boot up for a few seconds then lock up again. I even had the wheel spin and some sounds play from time to time. So back out to test. Macros Rom is back to 1 flash I ordered another NVRAM and still 1 flash. I tried Leons test rom also and I’m getting the same 1 flash. When the test chip is in I’m getting pulsing address and data lines. The U1 pin 40 starts low then goes high. The clock is pulsing at U1-37 and 25, all Riot chips are receiving the clock pulse as well. I have checked most if not all of the other logic chips and all of the logic appears to be correct, some I’m not sure the input is right but the output is right for the type of gate. I have checked continuity between the lines going between U1-U6. I checked to make sure the legs wean't some how shorted to ground or the voltage. The only thing I can think of that could be is either the delay or memory protect circuit since they feed the 5101 ce1/ce2 but I’m not sure what to look for at this point. I want to add in case it might help if I connect the reset board even when it was working it would constantly reset the mpu, it seemed to be a time pulse not random resets.

So if you read all of this and I didn’t loose you and have any have any ideas whats going on please post. I know I am missing something here just not sure what.
Thanks in advance.

#3 5 years ago
Quoted from acebathound:

A memory or EPROM issue will cause weird things to happen.
I'd focus on getting the board to boot at the bench with the Marco test roms & getting to the point a continuous steady led flashes.
Did you check the solder work on the back of the 5101 socket?
Also the pads/traces and solder work for the daughterboard should probably be looked at. The daughterboard is a common failure point.. there's signals running THROUGH those pads so if they get jacked up from trying to replace the daughterboard, it could cause intermittent problems. Usually you can tell if there's an issue there as flexing the MPU some by pressing on the daughterboard will cause the machine to reset, stop working, etc.

thanks for the reply,

I have checked the solder with the 5101 everything that should have continuity does and what shouldn't doesn't. The daughterboad was replaced(not by me) with a Swemmer and both sockets have been replaced. The solder looks good on them and I thought I checked continuity but need to look at my notes.I'll try flexing the mpu board and see what happens, I have pushed on the daughterboard but that didn't change anything. I did find a chart on Pinwiki that has list of leg to leg connections I want to go though just to make sure there are no issues. The daughterboard has 4 leds that are lit and green. I looked and I can't find anything on it to tell me what they mean. I did make a mistake in the original post I'll change when I said U2 pins I meant U1.

Do you think the issue could be in the delay or memory protect circuit? Or focus on a different area?

#4 5 years ago

I had some time to check continuity between the chips and lines last night. I found something odd by mistake. I was checking A3 line and touched A4 on a different chip and it came up with 96 Ohms. I checked and this is the only line that does this. Is there a chance this problem is the MPU or one of the Riots? If it could be a chip any idea one to start with or just pick one? Non of them are socketed so I'll need to desolder them and socket them. I don't see any solder joints on the bottom that look like they are touching but if they were I'd think it would be a direct short instead of some resistance but I could be wrong. Any ideas?

3 weeks later
#5 5 years ago

I'm still having some issues with this. The newest problem is the Reset line is not reading high or low with the logic probe, I'm getting about 1.7V with a MM. On Z4 both pins 5 and 6 are high and 4 reads just 1.7V. The chip is getting its voltage and other logic lines are working. I replaced the chip and I am getting the same thing. I have looked at the traces and I can't see anything that might have any contact with the line. Does anyone have any ideas? I did post this in the Gottlieb thread too with no luck too.

#6 5 years ago

I'm still trying to figure this one out. I noticed that when you first turn the board on the voltage at Z4 pin 4 is a little over 4v then it starts to fall to about 1.7v. I thought it might be a chip so I took out all 3 Riots the MPU and game rom and its still the same. I'm not sure what I'm missing here. Does anyone know what could be doing this?

#8 5 years ago
Quoted from mrm_4:

Been watching to see if you find a fix. I have a similar issue with my gold wings not booting but it’s intermittent. I’m going to try replacing the socket the daughter board was modified to go into. If that doesn’t work I’m just replacing the MPU entirely. So frustrating.

Thanks, its good to know someone is watching lol. I did get a Piggy Deux from Pinitech thinking it might help as someone replaced mine all ready and I thought something wasn't right and desoldered their sockets. Those daughter boards are such a pain. I was looking some about getting a new board but I don't see anything available at the moment, I really hate to go that route but I may end up there. Good luck hope that will solve your issues.

#10 5 years ago
Quoted from mrm_4:

I got the piggy duex but because of the repairs done on my board it didn’t work. I cant figure out where the continuity is lost between U2 and TC1. Broken traces everywhere. Double bummer there. That piggy would’ve been perfect but the previous hacks done on this board are keeping it from working.

That sucks, I was lucky enough that the traces were all still intact. Sounds like it could be a lot of work.

#11 5 years ago

The saga continues. So I removed U2 , U4-U6 and the Piggy deux and I still had the same voltages at Z4 pin 4, around 3.7 then slowly dropping lower to around 1.7. So at least those chips aren’t dragging it down. I grabbed the old Z4 chip bent pin 4 on it so it wasn’t touching anything an now I get 4.5v constant even after 5-10 min. So up to that point it should be fine. Something from that socket on has to be dragging the voltage down. Just for the hell of it I took the chip out of Z4 and ran a jumper from pin 14 (VB) to pin 4, I know have the 4.5V in the circuit. I’m just about out of ideas here, the voltage has been staying around 3.7 so that is still a logic high and will work unless it falls again for some reason. Tonight I’m going to put all of the chips back check the voltage and if its 3.7 or better start the testing again with Marcos test rom and see what happens. If (when) the voltage drops I'll take the chips out again one at a time and see if there is any difference.

#12 4 years ago

Well, I did find the problem with this. So much self inflected pain here. I put a socket in for U1 at one point I wasn't sure if a problem was the MPU or not. Anyway when I soldered the pins is Pin1 is right next to the reset trace line from Z4. I took the socket out and saw there was a small spot of the trace that the green was were off and some flux around the area. I took cleaned it up and tested and I'm getting 4.2v constant there now. I know I checked there before but with out taking the socket off. Marcos test rom ran with no issues and its back in the machine. I wanted to give an update if anyone's been following any.

2 months later
#15 4 years ago
Quoted from Antman:

Ever get it fixed ?
I’m looking for a piggy deux but can’t find one available.

Yeah, I got it fixed the last issue was self inflected with a trace had a bare spot. I did order the Piggy Duex too and it works great. Its so much better than the original board.

I see Wayne replied too, keep an eye out when he gets more built or send him a message.

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