one port press both fire buttons

[ulao]

My issue seems to only be with player 1, the right port (player 2) is ok. I have test a few joystick all give the same results. 

 

So I'm pretty familiar with the 7800 controller port in how it works. I did check pin 5 and 9 and they are not shorted. 5 volts is present  pin 7. What else would make both buttons press left and right trigger at once? Guessing there is a pull up resister on the board that is shorted, missing, or damaged?

 

Looking at this

https://atariage.com/7800/archives/schematics_ntsc/Schematic_7800_NTSC_High.html

I thin maybe its the J3 (p1 p2)?

 

 

Edited June 7, 2022 by ulao

[+-^CrossBow^-]

Most likely the issue is with the TIA chip itself since it handles the fire button triggers in 7800 mode. Just had to tell a client recently the same thing when their player 1 was also registering both fire buttons. I confirmed it when I swapped it out with a spare TIA with video issues for testing and the buttons started working again normally.

[ulao]

the C0104444D ?

 

Where might I find one and hopefully not best electronics...

Edited June 7, 2022 by ulao

[Trebor]

10 hours ago, ulao said:

My issue seems to only be with player 1, the right port (player 2) is ok. I have test a few joystick all give the same results...

What else would make both buttons press left and right trigger at once? 

In the chance event the test here is the game Xevious, the difficulty switches modifies the behavior of the buttons. A possible configuration is for Player One, one button fires both weapons, while Player Two the weapons are separated between the buttons.

[ulao]

yeah was using  that game for a test. but.. I didn't know that switch changes it. 

 

but, no using the select button didn't fix the issue. Player 2 is ok, but player one always does both weapons. I reid to cycle thru all options trying each one. 

Edited June 7, 2022 by ulao

[Trebor]

7 minutes ago, ulao said:

yeah was using  that game for a test. but.. I didn't know that switch changes it. 

Taken from the Atari 7800 Difficulty Switches Guide post:

 

 

[alex_79]

It's worth noting that if there's oxidation inside one of switches, it will always read as if it's in "A" position. Try quickly toggling it back and forth a few times: this could temporarily restore conductivity. To fix it for good, spray some contact cleaner inside it (or replace the switch).

[ulao]

ok now I'm confused... 

 

I just played Pole position 2 and it is working with both button?

 

all select options for Xevious fire both for player one? and I know for a fact the default option is dependent  firing. 

 

Edited June 7, 2022 by ulao

[ulao]

4 minutes ago, alex_79 said:

It's worth noting that if there's oxidation inside one of switches, it will always read as if it's in "A" position. Try quickly toggling it back and forth a few times: this could temporarily restore conductivity. To fix it for good, spray some contact cleaner inside it (or replace the switch).

Switches? There is s select switch that is a momentary switch. Are you thinking of the 2600?

[alex_79]

No, just look in between the two controller ports. And check the thread linked by @Trebor above.

[ulao]

lol you learn something new each day. thx guys. 

[+-^CrossBow^-]

Interesting... another AA member sent me one of their modified NES controllers for use with the 7800 because they thought the buttons weren't correct since they were both doing the same thing. It was in fact the game Xevious they were using as well to test this and also didn't know about the difficulty switch selection changing between independent fire options or combined. 

 

I guess I shouldn't have assumed that had been checked. But in the case of the 7800 where I did confirm the TIA was bad, it was indeed a faulty chip. Their paddles would also register all the way to the far right as soon as you plugged them in and would never move plus the paddle trigger always being constantly registered so starting up breakout was instance on that console. 

 

@ulao yes, the only reliable source I know for TIA chips aside from pulling them from other donor parts consoles is Best and with their 1 purchase for live option on them... it makes is really difficult for someone who repairs these consoles since I obviously would need access to more than just a single TIA in my lifetime. The TIA much not be in that much demand but currently they sell for more than the Pokey chips do at Best so it might be time to look into a replacement for these?

 

[Trebor]

49 minutes ago, alex_79 said:

No, just look in between the two controller ports. And check the thread linked by @Trebor above.

 

47 minutes ago, ulao said:

lol you learn something new each day. thx guys. 

Here's the image from that thread with the added switch labels to ensure the different position settings are clear:

 

 

[ulao]

yeah I will admit I didnt read thru the page, just took your advice and tried the select button. Little did I know there was another select button. Alex explained it in text and I'm more responsive to that. Nothing you did wrong, just not custom to links I'm old school  but I really appreciate that I was about to swap chips!

 

[+Stephen Moss]

17 hours ago, -^CrossBow^- said:

Best and with their 1 purchase for live option on them... it makes is really difficult for someone who repairs these consoles since I obviously would need access to more than just a single TIA in my lifetime.

This has probably been covered before and prohibitively expensive even with crowdsourcing but if we had the netlist (or whatever is required) I wonder how many you could produce on a silicon wafer, perhaps combine the wafer contents so it had a mix of devices, for the various Atari Consoles.

I think I have seen a logic diagram for the TIA somewhere, maybe a Programmable Logic Array or FPGA could be used to produce replacements. 

[+-^CrossBow^-]

6 hours ago, Stephen Moss said:

This has probably been covered before and prohibitively expensive even with crowdsourcing but if we had the netlist (or whatever is required) I wonder how many you could produce on a silicon wafer, perhaps combine the wafer contents so it had a mix of devices, for the various Atari Consoles.

I think I have seen a logic diagram for the TIA somewhere, maybe a Programmable Logic Array or FPGA could be used to produce replacements. 

I'm sure it is possible. If FPGA solutions have been created for the Pokey and other custom chips, I figured it is only a matter of time before the TIA has a solution of its own?