robotron woes

Mizzou

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Ok, so I finally got my hands on a robotron...one slight issue. Every time the game boots it comes up with "ram error 31". 75% of the time the game will play fine, but every now and then in the middle of the game it will come up with the infanite rug, or the game will freeze while still allowing my character to move around the screen freely.

The power supply has been rebuilt and the guy I bought it from had the boards serviced by yellow dog before I purchased it. My first thought was maybe low voltage? But I am a total noob ( and I do mean TOTAL NOOB) and need to find out how to check the voltage across the boards and chips. Anyone want to help a noob out?
 
Check all the connections. Williams games are notorious for crusty connectors. Also check the ribbon cables. You might have one with an issue.

You could also try re-seating the RAM chips. I don't know where you have this game stored but all of my Williams games have an issue with the RAM chips becoming unseated in higher temperatures. All my games are in a building in back of my house that is not air conditioned.
 
Thanks! I'll start off with checking the connections. My arcade is in my basement, so no real climate issues there.
 
+1 on connectors.

First thing though, is you need to learn how to check voltages. If they are off, no amount of tinkering will make it magically work. Spend a lot of time searching Williams, Robotron, and even other games that are similar like Defender, Stargate, etc. on here, and read it all. Once you have an idea of how things work, you can proceed with some confidence, and ask questions with specific direction.
 
ok, went back thru and re-connected all the connectors..still acting up..I can get maybe 10 minutes in or so until it decides to reboot.

I've done some searching and even googling, but I have yet to find a nice simple guide to checking the voltage across the board for a williams game. I know this is a noob thing to ask and I am sorry, but does anyone have some nice easy instructions for someone who is not savvy at all at this?

I dont know what the ram error 31 is as I have yet to find anyone else who encountered it. When I run the diagnostic everything comes up ok...so I dont know what that is about. I guess I could go and reset all the chips, but I think the safer bet right now is to determine if it is a voltage issue before I go tearing things up.

EDIT: I just realized I posted this in restorations instead of under repairs..could someone make the move?
 
Replacing the RAM with 4164 DRAM chips will result in more stable operation, as well. If your power supply's 12V, -5V, or 5V voltages aren't stable, it can result in problems with stability as the RAM relies on all of those. The newer 4164 RAM will only need 5V for proper operation, which will make the machine much more stable should the 12V supply wander.

Our Joust machine also sometimes will randomly come up with Error 31. The rug test will come back infinitely often, but with black and orange stripes in a few spots. The power supply was found to not be great, and the RAM replacement has made it much more stable.
 
it has 4164 DRAM installed, sorry I forgot to mention that
 
Do you have another williams game so you can swap the power supply? I had mine rebuilt but it failed shortly after that due to another issue with it. Just because it has been rebuilt does not mean it will work indefinitely, or even for any length of time. There are three LED lights on the power supply - are they all on?
 
i'd replace the chip and maybe reflow the legs to that socket (i'd try just replacing first).

atleast you don't have the old steel pin 4116s in still.
 
What chip are you refering to?

The game seems to be reseting itself so my first thought is not enough juice and to turn up the +5 voltage...That being said I am a complete noob at this so I could be way off. It just seems like the symptom fits that. If I can figure out how to test the voltage and the problem persists then I can go from there and start resetting chips as needed. I just need to figure out how to test the voltage..again complete noob, sorry.
 
What chip are you refering to?

The game seems to be reseting itself so my first thought is not enough juice and to turn up the +5 voltage...That being said I am a complete noob at this so I could be way off. It just seems like the symptom fits that. If I can figure out how to test the voltage and the problem persists then I can go from there and start resetting chips as needed. I just need to figure out how to test the voltage..again complete noob, sorry.

the chip causing the ram 31 error. the 31 refers to the chip # and bank, the manual tells you how to figure out which chip (iirc it means bank 3 chip 1 (correct me if i'm wrong guys)), the manual tells you how to ID the trouble codes. (page 8 and 9 have the info about ram errors).

i'm guessing the machine also has a switching power supply installed and nolonger has the original PS board (or it was bypassed) as you said you were going to up the 5v (the original power supply had different resistors for this instead of a dial).
 
No its a rebuilt power supply, not a switcher..I'm not very familiar with williams power supplys so I'm trying to do some reading on them. Unfortunately, my sinistar has a switcher so I dont have anything that I can compare apples to apples with, so to speak.

I'll take a look at the manual and see what it says on that chip. The odd thing is that when I did the self test it would come up as no errors. I checked with the previous owner, sochx, he had all the boards serviced before I purchased it. When he got it back he saw the error but it never interfeared with the game play, so he didnt bother to send it back in to get it looked at.

What I REALLY want to do is figure out how to check the voltage to see if it is correct. If it is dipping below 5v then I would think that would be the culprit, no?
 
connections

Then again my Joust used to do this all the time til I put a switcher in it.......
 
Ok finally had some time today to g back and check and refasten all the connectors. Fired it up and payed maybe 20 minutes or so without it resetting. I'll have to do some more playing to see if I am out of the woods. I did look at the power supply and all three lights came up, so I seem to be good there.
 
Dang, went back and played some more tonight..Everything was going ok, then about 10-15 minutes in it reset it self..Dang!

Ok, so where would you all suggest I go from here?
 
Yep, I did that. It gets me back to my original theory which is power. It says to check the voltage across the chip whenever there is a ram error. I just don't know how to identify which pin is which. For example it says check that pin 1 is -5, pin 8 is +12, and pin 9 is +5. I looked thru the book and diagram and could not find this. I'm sorry if this is a completely stupid question, but I'm still learning all this
 
from the datasheets i found on the net it looks like vcc/vdd Pin 8 is the 5v line

pin 8 should be directly below the key mark (if the key mark is facing your right hand)

have you tried swapping that ram chip with another ram chip on the board and seeing if the error moves? that would rule out the chip or not.

The manual also has a pin out of the header pins which would tell you if the board is getting voltage at least to the headers.
 
Thats wierd..I'm looking at the manual on the klov robotron page and it is listing +12 as pin 8. Its on page 9 under the RAM remedy..

Is their a map of the ram pinouts somewhere that I am missing? I thought I saw something from yellow dog once, but I cant seem to find it.

I have not tried swapping out the chips yet, but your right that sounds like a good idea. I dont have a chip extractor, but I can try to run up to radio shack today before I go into work and see if they have one. Does it matter what chip I swap it with? Does it need to be in the same column or row or anything?

Thannks everyone for all your help!

EDIT:I think maybe I wasnt phrasing this right, how do I tell which pin on a chip is pin# 9, 8, etc. Do you just start at a specific point then count down the line? Little confused here
 
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i was going by the datasheet for the 4164's the manual covers the 4116's (tho i don't think this really matters).

you can use a small flathead screw driver and gently rock both sides out of the socket. be careful when re inserting as the legs are pretty thin and also double/triple check your work before you power up (check to make sure all the legs are in the right socket (and in the socket) as well as the key notch is in the right position).

doesn't matter where you pull the 2nd "good" chip from as long as you remember where it was so you know that that's the position code it will throw if it does.

pin 8 should be directly below the key mark (if the key mark is facing your right hand)


Something like this (excuse my poor text diagram)


16 15 14 13 12 11 10 9
_________________ Key (notch)
1__2__3__ 4_5_6_7_8
 
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