Stargate Problem

jbk

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My stargate gives me a "all systems go" on startup but then says an adjustment failure. It says "CMOS Rom Failure" The machine will work and play but the high score names are scrambled. It will not remember the settings after power down. Sometimes on startup it will have 72 lives and 40 smartbombs and be in freeplay, other times 1 life and 1 smartbomb. It will allow you to make adjustments and keep them while turned on. The machine has a switching power supply installed and adjusted for correct voltage. A Li battery has been installed in place of the old alkalines. There is no corrosion to the board itself and just a little on the original battery holder before replacement. Where is the CMOS and what do i use for replacement?
 
You'll have to lead me by the hand, I'm new to williams machines. 1C being a plug or chip?
 
1C is the CMOS chip. You need to measure the voltage from pin 18 to ground. Pins are numbered counterclockwise from the notch on the end of the pin with 1 being the first pin on the left side.

You can also measure it at the end of D10 (the first diode just to the left of the batteries).

ken
 
Well your voltage is in range as the chip requires 2volts.

I seem to recall something about doing a reset of the cmos in the manual, perhaps that's al it need. You might try that before delving into chip replacement.
 
I don't have a manual, I'll have to go try and find one. If I do need to do a replacement, what is the correct chip to order from bob roberts?
 
If you press the advance button you will either get the diagnostics or the bookkeeping and feature adjustment screen. If you go to the feature adjustment screen and scroll down, oneof the options is to reset high scores and another is to reset factory defaults. Set both of those to yes and exit. That should reinitialize the CMOS.

You can also pull one of the batteries while the game is off and turn it on. That should force the CMOS to be re-initialized, then put the battery back while the power is on.

It is possible that you are having the infamous switcher issue with 6809s (the CPU running in most classic Williams games).
There are other problems with running a switcher in a Williams cabinet that you should be aware of. Due to the design of the 6809 CPU, when it is powering down, the CPU will randomly write to the memory address space. If that is a ROM or dynamic RAM address, no big deal. The ROM will ignore it and the RAM will be reinitialized the next time anyway. But if that memory address is in the CMOS, you can lose your high scores or the settings. The Williams original power supply was designed to minimize this risk by having that large capacitor on the power supply board. This keeps the power to the CPU on for a few extra milliseconds, which is long enough for the CMOS protection circuit to detect that the 12VDC has gone down and to turn off the CMOS chip enable. This protects the CMOS from shutdown writes by the CPU. You lose that protection when you replace the original board with a switcher.

ken
 
I tried both options and it didn't help. When I run the RAM/ROM tests I get CMOS as a write failure with no numbers on the board 7 digit CRT. It very well could be the switcher issue. Is the only solution to rebuid the original power supply. The PS has the two bottom lights on when the PS is connected and all three lights on when it is unplugged. I have never worked on a williams arcade prior to this one and a switcher seemed to be a good fix, maybe not. Could the best solution be rebuilding the original PS and replacing the CMOS chip?
 
Tried it, looked a little silly, no better results. Looks like I'm gonna try rebuilding the OE power supply. Thanks.
 
I don't have a manual, I'll have to go try and find one. If I do need to do a replacement, what is the correct chip to order from bob roberts?

You can get the manuals from arcarc.xmission.com.

Here is a link to the Stargate schematics: http://arcarc.xmission.com/PDF_Arcade_Williams/Stargate_Drawing_Set_(16P-3002-103)_Dec_1981.pdf
Here is a link to the Stargate Instruction manual: http://arcarc.xmission.com/PDF_Arca...nstruction_Manual_(16P-3002-101)_Oct_1981.pdf

The correct chip is a 5114 CMOS RAM chip. I am not sure if those are available any more, but I think there is a 6114 which is pin compatible.

ken
 
Last edited:
fix

Just installed a 5114 cmos chip and socket from bob roberts. Problem resolved, machine adjusts and no longer gives the cmos error. Also, got a PS rebuild kit from bob, gonna go ahead and put it in to see if I can take out the switcher. The switcher is not causing any problems but original is always better. Thanks to all who gave advice, another machine saved.
 
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