Stargate CPU help

dandydan1959

New member
Joined
Jan 27, 2010
Messages
175
Reaction score
0
Location
Ohio
Hi,

I have a Stargate that is displaying a 131 Ram error. I have read several post's and have checked the power supply and have the correct voltages on the ram. The rug pattern repeats on the monitor. I swapped ram 31 and still have the issue.

I have started through the Video recap troubleshooting charts and all signals are good until I get to the test for 1G pin 19. Pin 19 is low and stays low. The chart says it is the MPU Data buffers output. 2-9 are pulsing. I am not sure if that means that 1G is bad based on this test.
Can someone who is familiar with this test procedure tell me more about what to do next?
Thanks
Dan
 
another question

Hi, I also would like to know if 21256 ram chips can be used in place of the 4116's if I do the power plug mod i found on another post to use 4164's. It appears that the pin 9 and pin one are A7 and A8 and would not be needed in this config. Is that the case?
Thanks
Dan
 
Hi, I also would like to know if 21256 ram chips can be used in place of the 4116's if I do the power plug mod i found on another post to use 4164's. It appears that the pin 9 and pin one are A7 and A8 and would not be needed in this config. Is that the case?
Thanks
Dan

I haven't looked at the pinouts in a while, but I'd guess: probably not. Please provide a link to the post with the "power plug mod," and I may be able to consider the details.

If the PCB is modded per Matt's instructions linked below (including the 'optional step') then 41256 RAMs can be used.

http://www.scoresaves.com/misc/JustSayNoTo4116.html
 
Stargaze repair

Hi,
I completed the board mod as suggested and have a new set of 4164 ran installed. The 131 error remains. I started through the troubleshooting chart and the output at 1e pin 19 does not change states. The other test points on that chip do change states. I am stuck here not knowing if this is the source or a input from other chips. Could someone give me a nudge and tell me what this chip does and if it is the likely source?
Thanks
Dan
 
Correction. Chip with pin 19 not toggling is 1G

The troubleshooting chart tests 1G pin 19. This pin does not toggle and stays low.
Sorry for the confusion.
Dan
 
I'm no Williams expert (yet... just set up my Wms test rig yesterday), but I looked at the schems.

1G should be an LS245; verify that first, and carefully mind your pin counting. Pin 19 is the enable (aka gate) control. It is an INPUT to the LS245. This means that a lack of pulsing does not imply a problem with the IC under consideration. The source of the signal that signal is the 6809 CPU itself, pin 6. It's the "BA" (bus available) signal. Frankly, I'm a little surprised to read that it's expected to be pulsing (vice stay low)... but as I said, I'm no expert yet. If you've got a spare (esp known-working) 6809, try swapping it in.

Next time I get a chance to sit down and play, I'll look at that pin on a few of the CPU boards
I've got upstairs.
 
Last edited:
Update

Went back and checked 1D and 2D. Pins 13. They do not toggle either. I looked up the 1g chip and it appears that the pin 19 is a input. Traced it and it ties to 1D and 2 D pins 13 and to the CPU pin 6. I assume the CPU is the output in the circuit.
I replaced the CPU and no change.

The watchdog signal at 5H is low after hitting the reset button for several seconds and then toggles with the reset pulse. Is that normal?

Any help is appreciated.
Thanks
Dan
 
Have you checked pin 7 (should be pulsing) of 3D, 3E, 4E, and 4F? These generate the address lines for the RAM.
 
Checked

Hi,
I checked 3d7 and the others. 3Dpin 7 is not pulsing all others were. What does this indicate.
Thanks
Dan
 
I think you nailed it

I looked up the 74ls174 and checked the chip layout. Compared the inputs to the other mux's and they are the same but the output of pin 7 is not pulsing. I guess I need a chip to verify but this is promising.

Thanks for your help. I will let you know tomorrow when I grab a chipto put in.
Thanks
Dan
 
Correction

Hi,
I quoted the wrong chip number for 3D. It is a 74ls153. Pin 7 does not toggle. I just purchased a replacement and hope to get it in and test it tonight. I will let you know the results.
Thanks
Dan
 
Up and on to next issues.

Hi,
I have a booted game. 3d pin 7 output was the culprit.

I have new issues to work on.
On game start the ship goes to the top of the screen. The switch for down does not work.

The screen background is yellow. I have blue green, red yellow. Characters look right.

Let me know if you have suggestions.
Thanks
Dan
 
I just fixed one, an hour ago doing the same thing. The color problem is in the video output section, it's either your color rams (which you can test with a probe) or it's one of your video shift registers. If you tie pin 23 of the #4 decoder (3G) to 5V, it'll put the game into cocktail flip. If that fixes your color, then your problem is one of the shift registers, or chip 2H, or 2C. If you look at the schematics you'll see what I'm talking about. Basically the four registers work if the screen is one way, and the other four make it work when it's the other way. In an upright you only need the ones in row I, in a cocktail it switches for player 2 to the ones in row J. If you force it to flip, it forces it to use row J.

So! If it flips and the screen looks the same, your problem is almost certainly chip 2c, 2b, 1b, or 1a. If it flips and fixes the problem, your problem is almost certainly in 1i, 2i, 3i, or 4i.

You can also try probing pin 13 (output) of 1i, 2i,3i,4i and see if it's pulsing.

My screen was yellow, 3i was bad and pin 13 was stuck high.
 
As for the ship being stuck, remember all the inputs are on the 'widget' board. Hell just unplug that thing until you get the screen right, then we'll work on that. (stuck switch, stuck joystick, bad diode, bad input on widget, ribbon cable issue)
 
Pin 19 on chip 1G is tied to the Bus Available (BA) signal of the CPU. This is only used by the DMA chips in Robotron and later games. Stargate doesn't have the DMA chips so there is no bus arbitration required. So it is tied low by the BA line of the CPU.

ken
 
Making progress

Hi,
We are making progress. The output of 3i is bad. Also found the 4049 for the up IC7 bad. Back to the parts store tomorrow.

Thanks to everyone for your help. It is great to have a community where people share their knowledge.
Dan
 
Keep in mind that output of 3i could be 'bad' because 2H (where it's connected to upstream) could be bad. So you might want to pick you up a 74LS257 while you're at the parts store to save you a trip!

That's the e.x.a.c.t. same place I had a bad signal though that made my screen go yellow too. Crazy.
 
Success

Hi guys,

I replaced 3i and that took care of the yellow background. I also replaced the 4049 on the input board. That took care of the stick down issue. Everything looks great. I have one last issue that is I have a CMOS failure. None of the high scores or screen items are scrambled. I checked the door switch and it it good. So I am going to check the logic on the 6809 tomorrow.

Any advise is appreciated. I appreciate all of the help you have provided.

I have $50 in paint, hardware and three chips. I got the game as payment for an hours work on a friends pinball. I will post pics when I finish it up.
Thanks
Dan
 
I had a few Williams boards that gave me CMOS errors initally...

I did the Lithium battery mod.

I then booted the game and went into the setup screen.

I reset High Scores and Retored Factory Settings. (Should reset the CMOS)

I then rebooted the game and all was well.
 
Back
Top Bottom