Paddle repair- Fire button moves paddle

[ianoid]

I have a weird Atari paddle problem. On a known good 4 switch, one paddle moves when the button is pushed. Of course the paddle dial is not moving, just the signal sent from the pot is changing. Note that it moves less depending on the position of the paddle dial, but never goes away. Inside it looks ok. The cord doesn't have obvious damage, but I'm thinking that is probably the issue. The other paddle of the pair works great. 

 

Any thoughts?

[Thomas Jentzsch]

Might be a short cut (cable, connector...). Into which direction does it move?

[stepho]

Disconnect the paddles from the 2600.

Put and ohms-meter (multi-meter in resistor/ohms mode, a cheap $10 meter from any electronics or car parts place will do) across the paddles' pins for the channel that moves.

Press the button.

If the resistance changes then you have a short between the fire pin and the paddle pin.

Open up the paddle to see if any internal connections have worked their way loose or if something is bridging 2 connections.

 

Connect the ohms-meter to the fire pin.
Does it change it's resistance when the paddle is swept?
Should be infinite resistance when the fire button is not pushed and 0 ohms when the button is pushed.

Anything beside infinite and 0 means a short - same as above.

 

Less likely that the cable itself is at fault but perhaps it has an almighty kink in it where it got pinched hard.

That might have broken a couple of internal sheaths and allow bare wires to touch - the kink should be obvious.

[+Stephen Moss]

As stepho indicated it sounds to me like there may be a short between the paddle pin and the fire button,

particularly if it is the left paddle that is affected as the paddle is on pin 5 and the fire button is on pin 4. 

Do you know if it has been repaired before, if it has that may be when the short, if there is on occurred.

 

However I don't think the testing methods stepho described will prove much...

If you connect a meter to the fire pins and and GND you will get always get either infinite resistance (no path through the pot to GND) or 0 (switch shorting the pot) regardless of if the is switch is shorted to the pot or not.

You would only get a non infinite resistance with the fire button unpressed if someone serious screwed up a repair resulting in both the paddle pin being shorted to the fire pin and the third terminal of the pot has been connect to GND in error (wiper and one end in parallel with the switch) as it should left unconnected to create a variable resistance instead of a variable voltage.

 

Try measuring the resistance between the paddle and fire pins, infinite resistance is open, 0 resistance is short. 
 

Edited August 22, 2019 by Stephen Moss

[stepho]

Stephen,

 

Both your method and mine should work. If there is a short to a paddle pin then measuring between the fire pin and ground would show a resistance above 0 but way below infinite. The resistance is of course from the path through the swipe arm and the track. Which will vary according to the position.

[ianoid]

Alright, I tested pins using a multimeter and couldn't really come to any conclusions. 

 

Then I went ahead and tested out the paddles again, and they worked fine. Perhaps there was something in the jack that was freed when I tested it and the short resolved. Very weird, because the first time I tested it, I plugged it in and unplugged it several times, and tested known good paddles as well in between.  All's well that ends well. Thanks for your help guys!

 

ian

[stepho]

Intermittent shorts are a common thing.
Possibly something is loose inside and sometimes sits in a nice spot and sometimes sits in a bad spot.

I would still open it up and look for anything obvious like wires coming loose or bits of metal or solder floating loose or a kinked cable (which often has internal breaks).