BobsterD
Member
Do yourself a favor and change all 6 pots.... I've capped many and the jitters will remain until you replace the pots. Just a test... try adusting the pots while it's on and you'll see how it affects the jitters.
G05 (Asteroids) - vertical jitters
- Thread starter jehuie
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OP
OP
Huh. I wouldn't have thought of that because those are the brightness and contracts pots right? Why would they cause any kind of jitters? I can try to track some of those pots down. Fry's Electronics might have them locally. I'll try to dig out the specs on them. Thanks for the tip.
EDIT: Never mind....see below...
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OP
OP
6 pots? Ok, I need to look closer because I only noticed 4 pots. 2 on the main board and the brightness and contrast on the deflection board.
EDIT: Ah, located inconveniently way back on the board are the linearity pots....I see them on the schematics. I'll give it a whirl. Thanks again!
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OP
OP
Well adjusting those two pots didn't help anything either. But again, I'm not sure how they would help since they only the screen horizontally as far as I can tell. And the jumping is vertical. But....since several of you mentioned success with this I'll track some down and report back.
OP
OP
Yep...R700 and R702....didn't see those either. Dang I must be getting old. Eyesight ain't what it used to be.....but I went through the parts-list for the board and am quite sure that I know where all 8 pots are now (6 on deflection board, 2 on game board).
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OP
OP
Dang...I bought the "G05 pot kit" from Bob Roberts and replaced them all. Fired it up and looked great until it warmed up. Then started jumping again. Any more great ideas out there? I'm stumped.
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Have you tried a known working 2nd game board?
I read once here on KLOV the capacitors on the game board can cause jumping
OP
OP
I read on Bob Roberts page that "big blue" can sometimes cause these kinds of jitters also so I replaced that. After about 2 and half games, the whole thing went nuts. Now I have random graphics garbage all over the place and the start buttons are flashing at about double speed. What the heck?
And no, because I don't have a known working board available at the moment.
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I will try and find the thread
vctrcollectr
Active member
Mine had similar problems once,you might just need to clean and re seat the socketed chips.
smello
Member
His site also mentions the big blue causing the start button flashing issues....
It was installed correctly?
Maybe it's bad?
OP
OP
I will try re-seating the chips and cleaning the motherboard contacts. It just seems weird that the game played correctly (other than the jumpy monitor) until I swapped big blue. It sure has a "cause and effect" feel to it. But it could be coincidence also. So I'll give that a try.
And I sure hope I put the thing in right. There's not to many ways to screw that up. And it's brand spanking new. I can try swapping the old one back in I suppose.
And I sure hope I put the thing in right. There's not to many ways to screw that up. And it's brand spanking new. I can try swapping the old one back in I suppose.
OP
OP
Cleaned the contacts and reseated chips. Still acts the same.
Swapped the original "big blue" back in. Still acts the same.
Put in yet another "big blue" that is also brand new. Still acts the same.
I seem to be cursed lately.
Swapped the original "big blue" back in. Still acts the same.
Put in yet another "big blue" that is also brand new. Still acts the same.
I seem to be cursed lately.
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The problem will stop when the correct part is replaced.
(Stating the obvious, I know)
I am an electrician, we use elimination as a fault finding technique. So I still suggest trying a known working board to eliminate that from the equation.
Maybe you could slip a few beers to someone local to bring their good PCB there
(Unfortunately I live overseas, so no good there)
Just a thought . . .
(Stating the obvious, I know)
I am an electrician, we use elimination as a fault finding technique. So I still suggest trying a known working board to eliminate that from the equation.
Maybe you could slip a few beers to someone local to bring their good PCB there
(Unfortunately I live overseas, so no good there)
Just a thought . . .
OP
OP
Yeah, it would take a lot of beer to pay for a trip from Austrailia.
I do know someone who has one near me but he's hard to get ahold of for a variety of reasons. But I'll give him a call.I pulled all the socketed chips out last night and cleaned them with Tarn-X. Some were pretty black. Now they are pretty and new looking. But it still does the same thing. Fast resets over and over, with garbage all over the screen. Does the same thing in test mode....except that then it beeps with every reset.
OP
OP
Ok, I thought I should go back to the original thread and keep it here so I won't get confusing....
I checked pin 40 on the cpu with my logic probe and it's pulsing. This means the watchdog is yelling at the neighbor right? So I tied together the watchdog disable tab to the ground. Then the flashing start-button lights went dark. Everything calmed down and the screen is blank. Spotkiller is lit but only veeeery faintly. Not sure what any of this means. Does it mean anything to any of you?
I checked pin 40 on the cpu with my logic probe and it's pulsing. This means the watchdog is yelling at the neighbor right? So I tied together the watchdog disable tab to the ground. Then the flashing start-button lights went dark. Everything calmed down and the screen is blank. Spotkiller is lit but only veeeery faintly. Not sure what any of this means. Does it mean anything to any of you?
I had something similar to this and it turned out to be the CPU, mine had a 6502, when in the Atari Schematics it was calling for a 6502A. Replaced that, and it worked....But your mileage my vary though.
;
OP
OP
Yeah, I read that thread. The thing is, my game was playing fine until this happened so I'm sure it's the right cpu. Of course, the cpu may have become fried in the meantime. But I'd rather not just shotgun the problem and keep buying new parts. I was hoping to actually track it down by tracing it out.
Unfortunately, I don't really know where to go from here.
OP
OP
I tried swapping the cpu with a known-good replacement and it behaves exactly the same. Apparently this is going to be really hard for a relative amateur like myself to track down.
Ok, I have a question....if I order the Asteroids high-score kit that will replace all the roms right? So if they happen to be the problem then that SHOULD fix it. What other components would automatically get replaced by sticking one of those guys in there? There is at least a remote chance that would fix my problem right?
Although I was still really hoping to actually figure out the problem......and fix it right.....
Ok, I have a question....if I order the Asteroids high-score kit that will replace all the roms right? So if they happen to be the problem then that SHOULD fix it. What other components would automatically get replaced by sticking one of those guys in there? There is at least a remote chance that would fix my problem right?
Although I was still really hoping to actually figure out the problem......and fix it right.....
