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right joystick port always firing - light sixer


AtariLeaf
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Bah it's been a bad few weeks, discovering items that don't work. Tonight it was my daily driver 2600 which is a light sixer. Plugged in Ocean City Defender and switched to game 3 where I noticed the right turret was always firing even though I didn't have a joystick plugged into it yet. So I decided to run some test with space invaders and asteroids on two player games and in space invaders the right gun always fired. In asteroids the right player would fire one shot when the round started and then nothing. I've been reading that the likely culprit may be a buffer chip called a 4050.

 

Would this be a correct starting point and is there a way to test it with a multimeter?

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Would this be a correct starting point and is there a way to test it with a multimeter?

Yes and not really - I mean there probably is, but its just faster to put a new 4050 in.

Would recommend a socket for the 4050 too.

I don't know if the "Zener Diode & 1uF axial capacitors for static protection" is applicable to a light sixer ( i think so).

That provides protection for the 4050 from the joystick ports.

https://console5.com/store/cd4050-cmos-hex-buffer-converters-atari-2600-5200-4050.html

https://console5.com/store/atari-2600-total-refresh-kit-new-capacitors.html

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Yes and not really - I mean there probably is, but its just faster to put a new 4050 in.

Would recommend a socket for the 4050 too.

I don't know if the "Zener Diode & 1uF axial capacitors for static protection" is applicable to a light sixer ( i think so).

That provides protection for the 4050 from the joystick ports.

https://console5.com/store/cd4050-cmos-hex-buffer-converters-atari-2600-5200-4050.html

https://console5.com/store/atari-2600-total-refresh-kit-new-capacitors.html

Thanks for the link, I'll pick up a bunch. I did a capacitor refresh kit from mojoatomic a few months ago but I don't think it included everything in your second link.

 

Will these sockets work for the 4050? https://console5.com/store/16-pin-dip-ic-chip-sockets-3m.html

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oh I stand corrected the fire button doesnt go to the riot chip, its the directions

 

So the 4050 it is then? I read some older posts about the TIA possibly being the culprit but the consensus seemed to be the 4050. Another solution is apparently to bridge two pins or cut them off altogether and solder the gap between the pins. Being completely new to soldering I wonder if that would be easier for a newb to attempt than completely removing a chip and resoldering in a socket. Although I wonder if having the socket would perhaps alleviate the problems these chips may develop over time.

 

BTW, how prevalent is it to get static to damage these chips? My systems usually stay in place. Is the act of plugging and unplugging controllers enough to do this? Is doing it with the 2600 plugged in a bad idea? I've never had this problem so never considered possible static damage to the chips unless I dragged the system along the carpet as I played (I don't do that, just sayin')

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it would be a good place to start

 

I dont have stat's on esd damage, I just seem to get a lot where one of the directional pins is always in some half on half off state and off you go, I imagine some winter morning with little feet shuffling against shag carpet going to plug a joystick in and zap

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BTW, how prevalent is it to get static to damage these chips? My systems usually stay in place. Is the act of plugging and unplugging controllers enough to do this? Is doing it with the 2600 plugged in a bad idea? I've never had this problem so never considered possible static damage to the chips unless I dragged the system along the carpet as I played (I don't do that, just sayin')

The diode and cap fix is an Atari bulletin fix- so it must of been a persistent problem on the early models.

Four switchers and later have the circuit protection built in - I think.

It says its for static protection, but I think hot swapping controllers may be just as much a problem.

 

On the Colecovision it's generally accepted that hot swapping is a main cause of frying the controller chip(s).

 

Here is the console5 wiki for the 2600 kit install info:

https://console5.com/wiki/Atari_2600

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Did you check pin 6 and 8 in joystick port for short? If it's shorted, it is not the 4050. A bad cap or diode could cause it, desolder or snip the pin off diode or cap to remove short and check the game to see if firing is normal. If there's no short, check the pullup resistor on pin 6 to 5v, without that the controller pin may behave erratically. Burned out resistor, broken resistor, bad solder joint or bad trace to the resistor could cause that.

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Did you check pin 6 and 8 in joystick port for short? If it's shorted, it is not the 4050. A bad cap or diode could cause it, desolder or snip the pin off diode or cap to remove short and check the game to see if firing is normal. If there's no short, check the pullup resistor on pin 6 to 5v, without that the controller pin may behave erratically. Burned out resistor, broken resistor, bad solder joint or bad trace to the resistor could cause that.

 

No I didn't try that. How exactly do I do that with a multimeter? This was the system by the way, that I had recapped with mojoatomic's kit a few months ago. I wonder if one of those parts was a replacement part that was bad?

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No I didn't try that. How exactly do I do that with a multimeter? This was the system by the way, that I had recapped with mojoatomic's kit a few months ago. I wonder if one of those parts was a replacement part that was bad?

 

With the console turned off, using multimeter set to ohm stick the probe and touch pin 6 and 8 of the controller port, If your 2600 is in pieces, it is easier to check the bottom at the solder spot. If it shows 0 or very low resistance, there's a short.

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At 20k setting, 1.0 is probably 1k ohms but that seems low. I checked mine and both are at same number so your port 1 may have a little problem. Try to desolder and remove one leg of a capacitor and diode connected to pin 6 of the controller port and check the resistance again.

 

If it is still low, and you don't see problem along the trace like solder blob, replace the 4050. If it goes up to 14k ish, then either the cap or diode was bad.

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I'll have to try this on the weekend, don't have the time until then unfortunately. Just on a cursory glance I see a capacitor that says 220k on it that seems to be linked to pin 6. I can desolder that pin and then I guess I follow the trace of that pin on the board to find a diode as well? Sorry for all the questions, still so new to all this.

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Pin 6 is internally pulled up through a 10K (or 10K & 220R resistor depending on version), with no controller inserted measure the voltage at the controller port between pin 6 and ground (pin 8, or metal tab on the 7805).

If you read about 5V then there is no short to ground or open between the 5V supply and the pin, thus the problem probably lies between pin 6 and the relative IC, or the IC itself.

If you read 0V then find the pull up resistor and measure the voltage across that, a reading of about 5V would indicate a short to ground, a reading of around 0V would suggest the problem lies with the pull up resistor(s) connected between the 5V supply and pin 6

 

If you suspect the problem lies with the pull up resistor(s) start with the 10K, measure the voltage between each end and ground...

a measurement of 5V at one end and 0V at the other - replace the resistor

a measurement of 0V at both ends either a bad joint (resolder) or a broken track.

a measurement of 5V at each end problem lies between resistor and pin 6 (broken track, bad joint pin 6 or the 220R resistor if fitted)

 

If you suspect a short to ground remove the capacitor connected between pin 6 & ground, if the short goes away replace the capacitor, if the short remains try running a sharp blade lightly between the controller port pins (or used a wire brush) to remove any possible "tin wiskers" and look for larger shorts from any bad soldering.

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I was getting odd readings of 1.5 or 1.6 but I'm pretty sure I'm not doing it right. I feel like an idiot because I really can't understand the lingo being used here. I don't know anything about electronics so I'm reading replies and scratching my head and running to google to try to decipher what the heck I'm reading and guessing where to stick the multimeters probes but probably getting it wrong. I was reading in other threads that nine times out of ten when you have a joystick port that acts like the fire button is always pressed it is almost always the 4050 so I'll replace the 4050 and put it a socket and hope that works, if not I'll replace some caps.

 

I appreciate everyone's help but I think I'm a lost cause because my brain can't decipher what is being said and I apologize for wasting everyone's time. :(

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I was getting odd readings of 1.5 or 1.6 but I'm pretty sure I'm not doing it right. I feel like an idiot because I really can't understand the lingo being used here. I don't know anything about electronics so I'm reading replies and scratching my head and running to google to try to decipher what the heck I'm reading and guessing where to stick the multimeters probes but probably getting it wrong. I was reading in other threads that nine times out of ten when you have a joystick port that acts like the fire button is always pressed it is almost always the 4050 so I'll replace the 4050 and put it a socket and hope that works, if not I'll replace some caps.

 

I appreciate everyone's help but I think I'm a lost cause because my brain can't decipher what is being said and I apologize for wasting everyone's time. :(

 

You aren't wasting anyone's time. This isn't just a site to talk about games...it is a resource of vast knowledge about all things gaming related. Mostly Atari...but other stuff as well. It also doesn't help that while we are asking you to check resistors and capacitors..etc, that Atari decided to silkscreen the damn component labels under the components when they are installed?!

 

But yeah to do something like checking voltage, you just set your meter to V-DC and then put your common probe point (Usually black color) to ground somewhere on the PCB and the other to the component legs while the system is on being very careful of course to not short the probe against anything else while doing so.

 

Also although the silkscreen labels are usually covered by the component on Atari boards, the labels you can see usually tell you what the component is in the label. So if something is marked R36 in this case...the R usually means it is a resistor. If it is C36..the C usually means Capacitor.

 

To make it more confusing in the case of Atari, they frequently used diodes and capacitors that looked just like resistors! So again it doesn't help that Atari decided it was a smart move to print the label for the components where the component covers it up.

 

If it makes you feel any better, I'm dealing with something similar on a rather interesting 7800 right now and I have a pretty decent understanding of what to look for and check and it still has me scratching my damn head on what is wrong with it.

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So I replaced the 4050 and the right joystick still fires with no stick plugged in. So it's not that chip. It must be one of the many caps, resistors, diodes, etc? But which one?

 

I bought a refresh kit from console 5, would one of those parts be the one that needs replacing?

 

I've read talk of "bridging" two pins to on the 4050 to stop this behavior. Should I try this or try to identify the offending part first?

 

EDIT: I pulled the one leg out of the 220k (C237) cap attached to pin 6 and the multimeter reading between pins 6 and 8 is now at 16 using 20k on the multimeter, same as pins 6 and 8 on the left joystick port. Does this mean this cap needs replacing? Should I hook up the 2600 and try it with the cap leg out and see if the joystick fires on its own still?

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Before you started pulling components, did you ever verify continuity of the trigger line from the controller all the way to the TIA pin for that controller (pin 35, if I recall correctly)?

Wouldn't a break in continuity through that circuit cause a "no fire" rather than a "continuous fire" condition? Or am I just misunderstanding what you're saying?

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Wouldn't a break in continuity through that circuit cause a "no fire" rather than a "continuous fire" condition? Or am I just misunderstanding what you're saying?

 

Well, before ArtariLeaf started removing components, if he'd verified continuity from the controller jack pin through to the PIA, it would help confirm or refute other possible causes of problems. TIA reads the trigger lines for both controllers. So if there was continuity from the pin to the socket, it would point to an issue with the IC.

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Wouldn't a break in continuity through that circuit cause a "no fire" rather than a "continuous fire" condition? Or am I just misunderstanding what you're saying?

the joystick operates by pulling low so a break would cause it to never fire, a short to ground would cause it to continuously fire

 

leaf do / have you tried swapping out the TIA

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