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right joystick port always firing - light sixer


AtariLeaf

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No I didn't swap the tia, I was going off what 7800fan said in post 14. So i put the probes on the multimeter on pin 6 of the controller and pin 35 of the tia respectively?

 

Also, maybe a dumb question, but if it was the tia wouldn't both joystick ports be affected and not just the right one?

 

EDIT - before I did anything else, I did quickly hook up the system just now and the right joystick port seems to be behaving properly again. With no joystick it doesn't auto fire and with a joystick plugged in it fires as normal. So it probably was this cap?

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No I didn't swap the tia, I was going off what 7800fan said in post 14. So i put the probes on the multimeter on pin 6 of the controller and pin 35 of the tia respectively?

 

Also, maybe a dumb question, but if it was the tia wouldn't both joystick ports be affected and not just the right one?

 

EDIT - before I did anything else, I did quickly hook up the system just now and the right joystick port seems to be behaving properly again. With no joystick it doesn't auto fire and with a joystick plugged in it fires as normal. So it probably was this cap?

 

Nope. TIA is an "integrated circuit" - it's got LOTS of circuits inside, and a flaw or imperfection can develop in one part but not the others. Some chips are more prone to issues than others and if you mess around with old systems long enough, you'll run into them. In 4-switch systems, 6532 RIOT chips seem to be problematic, or maybe I've just had bad luck. I keep running into machines where one of the difficulty switches doesn't function but the other is registers normally - switches are fine, continuity will be fine ... replace the chip, problem solved.

 

Small support logic can also fail. I've had a 4050 fail in a video circuit of an 800XL, I've had a bad 4011 chip inside a 5200 CX-53 Trak-Ball, one or more bad 4052 chips in a 5200 (these decode the controller keypad buttons) ...

 

Anyway, glad you seem to have ID'd the issue; the capacitor probably failed. You should probably replace it at some point.

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Thanks, now the problem is trying to find these locally. If the 80's Radio Shack was still around it would be easy. I gotta find a small local mom and pop store here in Windsor to keep shipping costs down. OR if I have to order online is there a kind of grocery list of cheap common parts like caps, resistors, etc that would be good to pick up all at once to save on shipping? A bunch of things that are common fail parts in a 2600 or similarly aged video game or computer equipment.

 

I get the impression that some of you experts who do a lot of this work would tend to keep a lot of these kind of parts on hand for just such situations and that might be a good way to go if I need to replace a small cap or resistor down the road.

 

BTW - a theoretical question - what if I continued to use the 2600 as is with the cap leg clipped as it is? Would it cause another part to fail with too much use or cause stress on other parts? I'm not going to but I'm curious as I try to learn as much as I can how these things work.

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I'm not positive here, but I believe it will work fine without the cap and the cap was likely put in for debouncing. Basically when you switch something on, it doesn't just happen. It actually causes a 'ripple' of sorts or states of on/off/on before it finally is actually just ON. This can cause some goofiness if a game isn't designed to handle it properly, and so a cap can be used to help reduce or remove this ripple like effect. I'm likely not explaining that very well, but if you look up debounce on electronics you will learn more than you ever wanted to on it. But again, my guess is this is why the caps were put into place.

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If I put in a new cap and the same firing issue happens then what? Keep the cap out or consider that it may be the TIA?

 

No. If the right joystick button is working correctly, by definition the TIA isn't the issue. If the trigger starts misbehaving after you replace the cap, your cap is defective or potentially installed incorrectly perhaps.

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Can anyone point me in the right direction on a place like Digikey for the cap I need? Finding one locally has been pretty much futile. It's one of the ones by the joystick ports and says 220K

 

If I do buy from Digikey, is there a bunch of different common and caps and resistors, etc I should be purchasing for down the road?

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I like Mouser and here's a quick link: http://www.mouser.com/Passive-Components/Capacitors/Ceramic-Capacitors/Ceramic-Disc-Capacitors/_/N-5g90?P=1z0x8hsZ1yvneqiZ1yvfzm2Z1z0z7l5&Keyword=220pf+capacitor&FS=True

 

Take your pick. They may not look the same but they generally behave the same and 2600 isn't so picky that it'd refuse to work if you didn't use exact match as original cap.

 

As for resistor, usually they won't fail in a 2600. But if you plan to do a lot of repair or electronic projects, grab resistor kit off eBay. I got something like 100 different common values.

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So just looking at the first one that comes up:

 

http://ca.mouser.com/ProductDetail/Vishay-BC-Components/D221K20Y5PL63L6R/?qs=sGAEpiMZZMt1mVBmZSXTPGZfUmf9Bhnh96E7McwC9LY%3d

 

there's all kinds of little variables like votage ac, voltage dc, tolerance, etc to these things that are beyond me. So as long as they are 220pf like the original (which says 220K) I should be fine? There's no need to worry about these variables?

 

Second question (I hope people aren't getting sick of my questions) Are there any other common parts you can point me to that I should get while I'm at it - common replacement parts that would work on the 2600 or are common on other systems from the late 70's or early 80's?

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7805 voltage regulators

 

voltage matters but its not that big of a deal with ceramics, that's a 500v part in a 5 volt system

 

So I should get a lower voltage cap then? It looks like 100v is the lowest they have

 

If my understanding is correct, that is just the max voltage that the cap can handle? So for a 5 volt system like a 2600 it's overkill but won't harm anything?

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