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7800 controller port (?) problem


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#1 shear_xear OFFLINE  

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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  

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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  

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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  

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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  

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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  

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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  

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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  

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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  

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Posted Mon Jul 17, 2017 12:38 PM

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



#10 shear_xear OFFLINE  

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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  

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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  

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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  

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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).



#14 -^CrožBow^- OFFLINE  

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Posted Mon Sep 4, 2017 8:39 AM

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

 

What became of this? I've got one now I'm AV modding for someone and in my diags testing I found that player 2 can't move left at all and it registers both fire buttons being triggered constantly. 1 player games work fine though.



#15 shear_xear OFFLINE  

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Posted Mon Sep 4, 2017 9:47 AM

Hi. I haven't had a chance to get to it for awhile. Sorry...

#16 DrVenkman ONLINE  

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Posted Mon Sep 4, 2017 10:00 AM

 

What became of this? I've got one now I'm AV modding for someone and in my diags testing I found that player 2 can't move left at all and it registers both fire buttons being triggered constantly. 1 player games work fine though.

 

Boy the directional issue sounds like the RIOT , though I wonder about that fire button issue. On the 2600, FIRE read by the TIA as are the paddle lines. If there's not debris or something obviously wrong with the board like shorted traces, I guess it's possible both chips are going bad. I mean, I've got 2600's that have had problems with each of those independently though not at the same time. 



#17 -^CrožBow^- OFFLINE  

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Posted Mon Sep 4, 2017 10:35 AM

Yeah...I've actually had to replace the RIOT in my primary 7800 when I found out the AVox+ wouldn't work properly on it. Very odd with the RIOT was that normal game play was working fine but some 2600 homebrews like Stay Frosty for instance I had trouble jumping properly and some other stuff that I had no idea it was the RIOT until I got the AVox+. The one I'm AV modding, the client is now sending me a junker 2600jr he has on hand. So it will become the donor for one or both chips depending on my testing. I had planned to replace the RIOT first to see.

 

This 7800 has been an interesting animal. After I first put it together, it would turn itself on when inserting a game cart?! Later found out that something with the RF shielding is shorting against something. Once I got the shield in just the right place, it stopped doing it and was working normally. So strange...






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