Really need help with stargate

verymotley

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First I would like to says thanks to all who offered advise on my sick Jungle Hunt. I am happy to report that it is now running perfectly. Now onto a bigger problem...stargate.
I have owned this game for 11 years, has not worked for 8 years(got married, had kids, pushed it in the corner) now it's time to get it running. Last time it worked it was just a bad solder on the 6 pin connector from the cpu board, causing the screen to go on and off. I tried to fix it myself with no soldering experience and really damaged the monitor chassis pulling up the pad all around the pins. Now that I have more experience and knowledge I spent some time running jumper wires from each pin to the next point on the board. I did a continuity test on each one and they all passed, but all I got was a red screen with a black line from top to bottom and then it went to a black screen. No game play at all on coin-up. There is neck glow present. Now I don't know if it cpu causing this or if it is still a problem with the monitor chassis. I checked for the 5 volts and all the fuses and just don't know where to go from here.
 
1) Are you seeing all three LEDs on the power supply board lighting up? If not you need to fix that first. If all three are lighting up, get your meter out, pull the output connector and verify with a meter that you are seeing the correct voltages. The LEDs are just an indicator that the basiic voltages are present. They may be higher than spec. Or there may be residual AC leaking through.

2) Are you seeing anything on the 7 segment LED on the ROM board. Normally, you will see diagnostic messages flash on the LED. The first digit is what part is bad: 1 = RAM, 2=ROM and then the next two digits are for the position of the bad part.

For example, 2-0-7 would be a bad ROM 7. 1-2-7 would be RAM 27 is bad (Bank 2 chip 7).

1-3-1 is a special case as it could be a number of issues. RAM 31 is the first RAM chip tested and if there are addressing issues or power issues this is frequently displayed.

ken
 
I replaced the power supply with a bob roberts conversion kit a while back and it is putting out 5 volts, so that should be good.
2. The led shows nothing at all until I power the game off, then it flashed for a second.
 
You need to check the other voltages. The RAM used on the Williams MPU boards uses +5V, -5V and +12V, IIRC. If any of these other voltages are not correct, the board will not boot.

The connector cable from the MPU to the ROM board may be bad or you may need to recrimp it. The following link shows the correct way to recrimp the connectors (ignore the part about cutting the ribbon cable unless you are going to replace it): http://www.arcadesolution.com/ribbon.html

If you have a logic probe, check the reset pin on the CPU chip (pin 36, IIRC). If it is pulsing then you will need to do some logic checking in the timing and watchdog circuits.

ken

Edit: See rant in the other Stagate thread (http://forums.arcade-museum.com/showthread.php?t=154582) for why switchers are a bad idea for WIlliams games.
 
I re-crimped the ribbon cable and also switched out the whole ram board and the led will still not show anything. Checked the +5, -5 and +12 and are all present. I now am back to a red screen though. Also used meter on all components on rom board and it is getting power but the led does not light up. I posted a pic of the damaged monitor chassis if it helps at all. Not sure if it shows enough detail to determine if is is fixable or should just be replaced.
 

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Does the game still not coin up? Even if the monitor board is damaged, the game will coin up if the rest is working properly.

Do you still have the original PS around? If so, order Bob's rebuild kit, shotgun it and reinstall and see what happens.
 
I posted a pic of the damaged monitor chassis if it helps at all. Not sure if it shows enough detail to determine if is is fixable or should just be replaced.

looks eminently fixable to me, if that is the issue.. if you are concerned you could send the chassis to one of the monitor repair guys and ask them to work it over.
 
.... Checked the +5, -5 and +12 and are all present. .

measure the voltages at the RAM IC corners (pin 16 is ground, so measure the other three corners) and post the actual value.

+5v should be ideally around 5.1v at the PSU PCB as 5v rail is critical to the whole system operation. and MUST be greater than 4.75v and less than 5.25v

-5v should ideally be around -5.0v +/- 0.5v, and

the 12v rail should be 12.0v +/- 1.2v.

ideally the centre values are best for all ps rails. -5v & +12v are critical to memory operation if using 4116 rams.
 
measure the voltages at the RAM IC corners (pin 16 is ground, so measure the other three corners) and post the actual value.

+5v should be ideally around 5.1v at the PSU PCB as 5v rail is critical to the whole system operation. and MUST be greater than 4.75v and less than 5.25v

-5v should ideally be around -5.0v +/- 0.5v, and

the 12v rail should be 12.0v +/- 1.2v.

ideally the centre values are best for all ps rails. -5v & +12v are critical to memory operation if using 4116 rams.

Pin 1, -5.09 volts
pin 8, 12.44 volts
pin 9, 5.09 volts
All rams checked the same values
 
At this point, ignoring the monitor, if the game boards are working correctly you should get some indication on the LED on the ROM board. Normal operation is a 0, errors flash a sequesnce of 3 numbers. The first number = the component that is bad (1=RAM, 2=ROM) followed by the 2 digit location. For RAMs the first digit is the bank (1,2,3) and the second is the chip number (1-8). For ROMs it is the zero padded ROM number (01-12).

If you are not getting this indication, it is highly probable that the CPU (the 6809 chip) is not functioning correctly. This is normally caused by one of several issues:
1) The CPU chip is bad.
2) The clock circuit is not producing the correct clock pulses.
3) The watchdog circuit is malfunctioning and repetitively pulsing the RESET line on the CPU.

There can be other issues, but those are the ones I have commonly seen.

To diagnose these you will need a logic probe or an oscilliscope.

ken
 
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