Jump to content

Photo

7800 controller port (?) problem


12 replies to this topic

#1 shear_xear OFFLINE  

shear_xear

    Star Raider

  • 50 posts
  • Location:Illinois

Posted Sun Jul 16, 2017 9:54 PM

Hi everyone. I just received a 7800 that has a weird issue that I've never seen before. I can play single player games perfectly on the system, but when I try a two player game the second player just moves automatically to the left. Anyone know how I can possibly resolve this? Thanks!

#2 Trebor OFFLINE  

Trebor

    River Patroller

  • 4,127 posts

Posted Mon Jul 17, 2017 5:33 AM

Have the controllers been switched to see if the same problem occurs for the second player?



#3 Jouster OFFLINE  

Jouster

    Space Invader

  • 33 posts
  • Location:UK

Posted Mon Jul 17, 2017 5:41 AM

I have a similar problem with one of my consoles.

It automatically fires on port 2 without a joystick attached  :-o



#4 DrVenkman ONLINE  

DrVenkman

    Stargunner

  • 1,940 posts
  • Back off, man! I'm a scientist.
  • Location:KMBT

Posted Mon Jul 17, 2017 7:02 AM

I’d suspect TIA and/or RIOT chip. One of those has joystick directional signals and the other controls triggers, as I recall, but it’s been a long while since I looked at the schematics.

#5 shear_xear OFFLINE  

shear_xear

    Star Raider

  • Topic Starter
  • 50 posts
  • Location:Illinois

Posted Mon Jul 17, 2017 8:19 AM

Yes, it is only the second player. I have several broken controllers that autofire on button 2, but this is definitely the Atari.

#6 shear_xear OFFLINE  

shear_xear

    Star Raider

  • Topic Starter
  • 50 posts
  • Location:Illinois

Posted Mon Jul 17, 2017 8:21 AM

I have several parts boards for the 7800 if it is one of the chips. Which chips are the TIA and RIOT?

#7 Trebor OFFLINE  

Trebor

    River Patroller

  • 4,127 posts

Posted Mon Jul 17, 2017 8:31 AM

Two larger IC's on the lower right hand side of the motherboard.  TIA on top / RIOT on the bottom.

 

Here's a quick pic/label of the 4 major chips:

 

7800MBLABELS.png

 

 

 

 

 



#8 shear_xear OFFLINE  

shear_xear

    Star Raider

  • Topic Starter
  • 50 posts
  • Location:Illinois

Posted Mon Jul 17, 2017 9:17 AM

Thanks, Trebor! I knew the Maria (kinda stands out), but always wondered about the rest. I will swap those out then. Thanks everyone!

#9 -^CrožBow^- OFFLINE  

-^CrožBow^-

    River Patroller

  • 4,895 posts
  • Collector of Fine Atari and Sega Antiquities!
  • Location:Ivory Tower, Fantasia (Oklahoma)

Posted Mon Jul 17, 2017 12:38 PM

I would start with replacing the RIOT first and test from there.



#10 shear_xear OFFLINE  

shear_xear

    Star Raider

  • Topic Starter
  • 50 posts
  • Location:Illinois

Posted Mon Jul 17, 2017 4:28 PM

I replaced the RIOT first, but it still has the problem. I'll have to try the other one tonight...

#11 DrVenkman ONLINE  

DrVenkman

    Stargunner

  • 1,940 posts
  • Back off, man! I'm a scientist.
  • Location:KMBT

Posted Mon Jul 17, 2017 6:09 PM

I replaced the RIOT first, but it still has the problem. I'll have to try the other one tonight...

 

If the RIOT is known to be good, and you've got a socketed board, verify that all the pins are making good contact with the socket wipes. If there's nothing wrong with the chip or the socket, you'll need to pull out a multimeter and verify continuity all the way from the controller jack pin all the way to the chip. Something is shorting the pin making the system think the controller is being held. There's probably a tiny piece of conductive debris (solder blob from prior mods or repair work?) shorting the pin, or you've got a shorted capacitor on the line.



#12 shear_xear OFFLINE  

shear_xear

    Star Raider

  • Topic Starter
  • 50 posts
  • Location:Illinois

Posted Mon Jul 17, 2017 6:28 PM

Only one of the ic has a socket, and it isn't the RIOT. I just desoldered the old one and took one off a parts board. I will check to see if there something wrong between the chip and the port. Maybe I will replace the capacitor first. Thanks!

#13 DrVenkman ONLINE  

DrVenkman

    Stargunner

  • 1,940 posts
  • Back off, man! I'm a scientist.
  • Location:KMBT

Posted Mon Jul 17, 2017 6:36 PM

Only one of the ic has a socket, and it isn't the RIOT. I just desoldered the old one and took one off a parts board. I will check to see if there something wrong between the chip and the port. Maybe I will replace the capacitor first. Thanks!

 

Ah, too bad. :( I always recommend installing a socket if you remove an IC from a soldered board. That way on the off-chance your replacement chip is wonky or fails again, you can replace it more easily (bitter experience - having purchased two 2600's over the years with bad RIOT chips).






0 user(s) are browsing this forum

0 members, 0 guests, 0 anonymous users