TailChao Posted September 25, 2019 Share Posted September 25, 2019 Cross answering with this, just in case anyone else runs into a similar issue. The four paddle inputs (I0 - I3) have indeterminate states without a ProLine (or compatible) joystick attached. Usually they'll stay low, but on certain units they'll drift high after the TIA warms up - or just immediately. This can be interpreted as spurious presses by game software using the two-button input mode, and seems to get worse with age. Xevious starts up in two-button mode, regardless of the left difficulty switch's state. It'll only switch into one-button mode when it detects a VCS style press. So if you're using a ProLine controller and your paddle inputs are hosed - it'll just keep firing. Galaga operates exclusively in one-button mode, so if it's working that at least indicates I4 and I5 could be fine. But it doesn't say anything about I0 - I3. Thing to try... Try using a single button controller with Xevious and see if it works. Check R36, R37, R38, and R39 to make sure they're in spec. Replace the TIA. Replace the 7805. 1 Quote Link to comment Share on other sites More sharing options...
thenickman100 Posted September 25, 2019 Author Share Posted September 25, 2019 9 minutes ago, TailChao said: Galaga operates exclusively in one-button mode, so if it's working that at least indicates I4 and I5 could be fine. But it doesn't say anything about I0 - I3. Galaga only worked fine after I removed the TIA and put it back in. Before I tried that, every game--including Galaga--was experiencing the same issue. Xevious is the game that caused the 7800 to act up in the first place, though. Quote Link to comment Share on other sites More sharing options...
TailChao Posted September 25, 2019 Share Posted September 25, 2019 22 minutes ago, thenickman100 said: Galaga only worked fine after I removed the TIA and put it back in. Before I tried that, every game--including Galaga--was experiencing the same issue. Xevious is the game that caused the 7800 to act up in the first place, though. This definitely sounds like a bad TIA or a really lousy continuity issue. Do you have another TIA to swap in and try? Quote Link to comment Share on other sites More sharing options...
+Mitch Posted September 25, 2019 Share Posted September 25, 2019 If reinsertIng the TIA fixed it, then it could be a bad socket as well. Mitch Quote Link to comment Share on other sites More sharing options...
thenickman100 Posted September 29, 2019 Author Share Posted September 29, 2019 On 9/25/2019 at 4:40 PM, TailChao said: This definitely sounds like a bad TIA or a really lousy continuity issue. Do you have another TIA to swap in and try? Unfortunately, I do not. I might pick up a 2600 at some point to try the TIA, but I doubt it will be anytime soon. If one game is causing it, is there any way it is overloading the board/TIA? As to your other suggestions, I already reassembled the system and returned the game. I'll probably stay away from 7800 repros from now on, aside from homebrews. Quote Link to comment Share on other sites More sharing options...
TailChao Posted September 29, 2019 Share Posted September 29, 2019 12 hours ago, thenickman100 said: Unfortunately, I do not. I might pick up a 2600 at some point to try the TIA, but I doubt it will be anytime soon. If one game is causing it, is there any way it is overloading the board/TIA? It's possible, but usually if a cartridge is causing a supply rail to sag you'll see other symptoms like video issues or instability. The whole input block on the 7800 is extremely fragile - so the TIA, RIOT, and ProLine support circuitry could have been damaged years ago and it's just now that the components are starting to fail. Quote Link to comment Share on other sites More sharing options...
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