How do you test continuity without harming circuitry?

Rekrul · Master of C64 Joined: 05 Aug 2009 Posts: 1117

As the title says, how do you test for continuity without harming delicate circuits?

I apparently killed a Sidewinder joystick by using a small meter (powered by a couple AA batteries) to figure out which pins in the connector were connected to which wires at the board connector. Why did I do this?

I found a Sidewinder Precision Pro in the trash, but with the cord cut off. I found an identical joystick at Goodwill for $2. I thought if I figured out what was connected to what, I could fix the other one.

Only problem is that now, the one from Goodwill, which was working perfectly, no longer works. Nothing registers and the buttons just flicker on/off.

If you're wondering why I haven't tried swapping the cable to the other one yet, it's because it's the only set of wires that's soldered rather than just plugged in. So I either have to unsolder it, or cut the wires.

I know, I should learn not to mess with things, but I can't help it, I'm a tinkerer.

So, other than not opening it in the first place, what could I have done differently to figure out the cable connections without harming the electronics?

Catboy · Groupie Joined: 19 Mar 2009 Posts: 261 Location: Germany

I would like to see a picture of this joystick's main board...

Normally, a digital C64 joystick only consists of a few switches that pull the relevant line to ground. They cannot be damaged so easily.

Nevertheless, if there's some kind of "rapid fire"-circuit built inside, that chip might not survive any testing at wrong polarity.

Strange problem. Does the "Sidewinder" contain a fuse which you may have blown during testing??

-Catboy

Rekrul · Master of C64 Joined: 05 Aug 2009 Posts: 1117

Catboy wrote:

I would like to see a picture of this joystick's main board...

Normally, a digital C64 joystick only consists of a few switches that pull the relevant line to ground. They cannot be damaged so easily.

Nevertheless, if there's some kind of "rapid fire"-circuit built inside, that chip might not survive any testing at wrong polarity.

Strange problem. Does the "Sidewinder" contain a fuse which you may have blown during testing??

A Sidewinder Precision Pro isn't an Atari digital stick. It's a Microsoft analog joystick with 8 buttons, throttle control, twist handle and shift button. The board has one main IC and a bunch of other components, all surface mounted. It's meant to be plugged into a traditional gameport, although it was designed so that you can use a simple adapter to connect it to a USB port. See here;

http://www.amazon.com/Microsof...B00000JDFT

Giana Brother · Posted: Tue Apr 10, 2012 11:34 pm Post subject:

"Reverse the polarity" Laughing

80's TV cliché number 34.

Hidron · Posted: Wed Apr 11, 2012 5:27 am Post subject:

Giana Brother wrote:

"Reverse the polarity" Laughing

80's TV cliché number 34.

Is there a full list somewhere?
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Giana Brother · Posted: Sat Apr 14, 2012 9:20 am Post subject:

Theres a website
http://tvtropes.org/pmwiki/pmw...sePolarity

eslapion

Rekrul wrote:

I apparently killed a Sidewinder joystick by using a small meter (powered by a couple AA batteries) to figure out which pins in the connector were connected to which wires at the board connector.

...

So, other than not opening it in the first place, what could I have done differently to figure out the cable connections without harming the electronics?

The answer is... expensive.

Modern high quality digital multimeters such as models made by Fluke and Meterman use extremely little current to verify continuity. Usually around 20 microamps.

What you want is "CMOS safe" continuity checking. My own Meterman 37XR is among the least expensive multimeters to have this feature.
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Rekrul · Master of C64 Joined: 05 Aug 2009 Posts: 1117

eslapion wrote:

The answer is... expensive.

Modern high quality digital multimeters such as models made by Fluke and Meterman use extremely little current to verify continuity. Usually around 20 microamps.

What you want is "CMOS safe" continuity checking. My own Meterman 37XR is among the least expensive multimeters to have this feature.

Thanks for the reply.

I still haven't done anything with those sticks. Actually, I spend most of today trying to figure out why my system was spontaneously rebooting. I gave it a good cleaning and it's been working since then, but I'm still holding my breath. I don't know if it was because of heat (although it wasn't especially hot today), a failing power supply, or just the dust buildup. Don't get me wrong, it wasn't growing fur inside, as I clean it every few months, but there was a fair amount as well as quite a few cobwebs.

It's been on for a few hours now and I notice that the air being blown out the back of the power supply is now much cooler than it was earlier. In fact around the time it started giving me problems, it felt like a blow dryer on low.

Rekrul · Master of C64 Joined: 05 Aug 2009 Posts: 1117

I thought I'd come back to this topic to officially announce that I'm dumb!

I opened both joysticks, cut the cord off the one I assumed I killed and connected all the wires to the one I found in the trash. Plugged it into my little gameport to USB adapter and it behaved exactly the same as the other one! I had no proof that the one from the trash was good, but it seemed strange that it would have the exact same problem as the other one, which I was sure I caused by using a meter to check the connections.

So for the hell of it, I plugged it into my soundcard. Guess what; It worked perfectly.

Apparently they're not compatible with the gameport to USB adapter. So there was probably nothing wrong with the other stick, it just didn't like how it was plugged in! Embarassed

Now I need to put a new cord on the one that originally had a cord. Unfortunately, I cut the wires off as close to the (soldered) connector on the board as I could, so I didn't leave myself anything to connect new wires to. Sad

If I try to unsolder the pins, I'll probably make a mess of it. Maybe I can cut the plastic housing away from the pins and that will leave enough to solder to.

So yeah, I should have thought of trying it connected to my sound card before I jumped to the conclusion that I had killed it, and cut off the cable.