Williams defender video problem

gunsablazin

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game boots up fine 4 leds on ROM board blink twice and the go out. game plays but the screen is flashes complete red and then complete yellow. you can hear the game playing perfectly fine, but just cant see it. now every now and then the video will pop up perfectly clear for a few seconds and then back yellow and red flashing !!!
Things ive checked/done
1. checked all connectors/wires
2. checked for cold solder joints
3. socketed CPU and Video Decoder chips
4. switched 6809 cpu out- same problem
5. switched video decoder chip- no help
6. reseated 5101 chip
7. swapped known good monitor out
8. ???? and a lot of hoping praying and crying...
Would the problem be in the video RAM chips (7489)?
Could it be the ROM board at all?
What other chips on the CPU has to do with the VIDEO????
IT's Basically an Intermittent problem....which are the worst kind to locate :-(
 
I don't really think it is a rom problem but you need to know the program is good BEFORE you start looking at the hardware.

Usually with intermittent problems, I just leave them run, maybe without video, and let fail/run for some time. I will also use compoent cooler/Freeze spray/Technician in a can/ to test chips,transistors,connections and cool heat sinks with. Many times the spray will make something work or fail, then you have a starting point.
 
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If the game is playing, then the issue is in the video generation circuits. My first guess would be to watch the outputs of the video RAM (the 74186 or 74286 chips near the video connector) with a logic probe.

Also verify the voltages at the RAMs. The voltages should be -5V, +12, +5 and ground at pins 1, 8, 9 and 16.

The other thing to try would be to recrimp the ROM cable.

ken
 
God, i know - the ribbon cables are terrible. Also hate how it's hard-wired into the ROM board( making it difficult to just simply replace the cable) Yea- no other game that i have restored has been so damn 'fragile' .

Thanks for the ideas- next chance I get I'll check the RAMs.... Your referring to JUST the VIDEO ram chips..... Not the 4116's right??? Since the game does boot and play
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Anybody have a JROK board either NEW or lightly used that they would like to sell???
 
YellowDog was telling ya to re-crimp the rom cable... pursue this.

God, i know - the ribbon cables are terrible. Also hate how it's hard-wired into the ROM board( making it difficult to just simply replace the cable) Yea- no other game that i have restored has been so damn 'fragile' .

Thanks for the ideas- next chance I get I'll check the RAMs.... Your referring to JUST the VIDEO ram chips..... Not the 4116's right??? Since the game does boot and play
*******************
Anybody have a JROK board either NEW or lightly used that they would like to sell???
 
Thanks saltbreez- I will try this actually before checking/doing anything else. I had this particular ribbon cable replaced about a year ago. But , these ribbon cables DO suck:) thanks again- ill let ya know
 
Ok - I've run out of time/patience - the game is at my brother in laws house and the wife(my sister) is over the game taking up space AND NOT WORKING to boot!
So, Who can fix this board and another board (that is a backup )if i send them to you(along with the ROM boards) one ROM board I'm almost positive works- the other well does have some kind of issue
Or who do you recommend - thanks Johnny
 
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