Alligator Clip Adapter

This is a great tool for troubleshooting guitars, and other things too.

The photo shows a "cable mount" 1/4" female jack, but you can use a regular "open" guitar jack as well.

You don't even have to solder the alligator clips to the jack. For a temporary adapter, just take two alligator clips and attach one end on each to the terminals of the output jack.

Troubleshooting Use

What would you use this for? Well, it allows you to test the guitar circuit all the way back up to the pickup without soldering anything.

Test pickups directly and quickly

When the problem is "no output," and nothing is visibly wrong, try clipping your alligator clips across the pickup leads (don't use the output jack's ground connection - it may be open!). By clipping directly to the pickup, you can see if there is output there. If you still get no output, the pickup may be bad. Disconnect one side or both and test again. If no signal, you have just determined the problem very quickly. Blown pickup.

Trace through circuits quickly

If the pickup is good, leave the ground connection where it is, and continue tracing back to the output jack. Whatever the order the signal travels in, follow that path. So, for instance on a traditional Strat circuit you would initially clip onto the switch terminal the pickup is connected to. Next, you'll clip to the output terminal of the switch. This is the wire that connects to the volume control. Check the switch terminal first, then the volume terminal. Next check the volume output terminal. This should bring you to the output jack. If you never lose the signal, but the 1/4" output jack still doesn't work, then check the grounds (this is why we left the ground connected right at the pickup).

Testing the pickup without strings

Note that both of these tests require getting the pickups to make some sound for you to test. Usually you'll have the strings off while serving the electronics, so how do we drive the pickup without strings? The usual method is to tap the pickup with a screwdriver. This should provide a decent noise to test with. Another idea is to use a tuning fork. The tuning fork has a slight advantage to the screwdriver in that it gives a better sense of the quality of the pickup. The downside is that it is difficult to hold the fork just over the pickup without slamming into it (the pickup is a magnet after all) or being too far away/too quiet.

Testing the circuit without the pickup

If the pickup isn't in question, and you need both of your hands, you can use an additional alligator clip adapter to inject a test signal. Because the guitar circuit is high impedance, pretty much any audio source you have will work fine as a test signal. The pickup will present the lowest impedance to the source; approx. 5kΩ or so per coil. Any line level output should handle 5kΩ no problem. A dedicated tone generator is the obvious choice, but since those aren't always handy you could try the headphone output of a cell phone, computer, or radio since at least one of those will probably always be in the repair shop.

Finding an intermittent bad connection

Injecting a constant signal is the best way to battle an intermittent issue. Monitor either some music or a constant tone (if you can stand that; I like it, but some folks don't) or even white noise, while poking, probing, pulling, etc every wire and component in the guitar. Eventually you should come across the intermittent connection, and much faster than if you had to be strumming the string or banging on a pickup at the same time!

Other Uses

I use the alligator to 1/4" adapter frequently to test speakers as well. Just clip onto the two terminals of a loudspeaker and you can now test the speaker easily without soldering.

A pair of them could allow you to make a temporary capacitor auditioner.