Stargate CMOS Issues?

texasmame

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So, have a Stargate that had some issues and got past those until I got to the CMOS. Turns out the CMOS was shot (5514). Swapped in a 2114 and it works normally now but it doesn't save scores correctly.

There are NO volts at pin 18 when the batteries are in, so somewhere along the line, it's dropping. When powered up, pin 18 gets just under 5v.

From the schematics, it looks to my novice eye like the 4.5 from the batteries goes through D10, then C3 and right in to pin 18 of the CMOS but I'm sure I'm missing something here.

First, I went directly from the 4.5v on the battery holder to the 18pin. It would scramble scores/settings when turned off. Remove the 4.5v and reboot - all better.

Then, thinking it needed the D10 in there, I ran it from the end of the D10 where it was about 3.8v to pin 18 - same result. Then from C3 to pin 18 - same.

Then, after following some traces, I found that pin 18 of the CMOS tested good for continuity to pin 6 of 6I but pin 6 seems to not be represented on my drawings - some others for 6I are, but not pin 6.

So, at this point, I guess I could replace 6I as it seems to tie directly to 1C pin 18 and hope that's it as jumping 4.5v directly to the CMOS pin doesn't seem to cut it.

Suggestions?
 
A 2114 does not have a low-power standby mode. Check the datasheet for the particular chip you are using, but most will not operate if Vcc drops below 4.75V.
 
A 2114 does not have a low-power standby mode. Check the datasheet for the particular chip you are using, but most will not operate if Vcc drops below 4.75V.



Ah, okay. I'll try and wire it up to a constant 5v to test that. Shouldn't be any issue with going directly to pin 18, correct, or will that make the batteries try and recharge (and maybe explode) due to the 5v that the machine applies to the 18 pin when the game is on? Does the D10 prevent the power from going "backwards" in to the battery? I'm thinking that wiring from the cathode terminal (white stripe) end of D10 to pin 18 would be fine as it prevents the power from going back to the batteries when the game is on.

Better still, if wiring direct to pin 18, could a rechargable battery then be used without issue? I've got to assume that's not the case as we'd all be wiring up Williams games with rechargables. ;)
 
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Yes, there is a diode that prevents the batteries from charging.
I don't see the point of trying to make a 2114 work here.... It would take some work, and the end result would be pretty poor (batteries would drain quickly). Much easier to just pop in the correct CMOS chip, or use a Dallas with an adapter and toss the alkaline batteries for good.
 
I agree with Matt. You're in a "beat it to fit" position, when there are better options available.

You either replace the chip, like for like, or go one of the high score kit routes. Unfortunately, there isn't a "MacGyver" path on this one that restores the game function with the chip you have installed.
 
Thanks guys. Yeah, just trying to work with what I had on hand but I've now got the proper chip on the way.

Just to clarify - after installing the proper replacement chip, running from the cathode end of the D10 directly to the 18pin should be acceptable as I'm not getting any voltage with the game off at 18pin with batteries installed now if not running a jumper wire right to 18pin.
 
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Without a detailed review of the circuit, and an understanding of how it is supposed to work, I can't say whether your plan will work or not.

However, I adhere to Occum's Razor, which is to wit, the simplest explanation is usually right.

So, you had a CMOS problem. You replaced it with the wrong CMOS.

You have the right CMOS coming. It worked before. Why would you change the design of the game?

If this were a nuclear plant, I'd ask you for the justification for the change - for example, there is a service bulletin that advocates this change.

Change for the purpose of trying things out is risky. It could be as simple as draining your AA batteries, or as complicated as letting the smoke out of your new chip.

Or, as old Uncle Nick used to say, "Why in the *#$&^*$&^ are you monkeying around with that? It ain't broke - why are you trying to make it broke?"

Uncle Nick was pretty blunt.
 
Check to make sure you are really getting voltage off the batteries. The Williams battery holders are notorious for looking good, but having corrosion or broken connectors so that power is not getting out of the battery holder. Replace with either a plastic battery holder or go the litium battery mod route and ditch the AA's.

You can also test the two diodes, but you have to do it out of circuit. They will almost always test good even if they are not when testing in circuit.

ken
 
Check to make sure you are really getting voltage off the batteries. The Williams battery holders are notorious for looking good, but having corrosion or broken connectors so that power is not getting out of the battery holder. Replace with either a plastic battery holder or go the litium battery mod route and ditch the AA's.

You can also test the two diodes, but you have to do it out of circuit. They will almost always test good even if they are not when testing in circuit.

ken

Okay. I have cleaned the battery holder well and am getting 4.5v off them but it drops to 3.8 or so when going through D10. Either way I may update the holder when the right CMOS comes in.
 
Thread wrapup: All better. The 6514 work like a charm. The 2114 work but you can't let the voltage drop below 5v or the saving is hit or miss.
 
Thread wrapup: All better. The 6514 work like a charm. The 2114 work but you can't let the voltage drop below 5v or the saving is hit or miss.

You mean 6114 right? I never tried them in that application. I use them as regular 2114 but some boards dont like them because they are too fast compared to the old 2114's. Its strange, most pac boards like them but some wont run on them at all.
 
You mean 6114 right? I never tried them in that application. I use them as regular 2114 but some boards dont like them because they are too fast compared to the old 2114's. Its strange, most pac boards like them but some wont run on them at all.

Yes, my bad - 6114.
 
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