Funny this thread is a current topic, because I just went out for a short 3 hour hunt with my 12x10 and had issues with it. I had traded my 15x12 for a used 12x10 somebody had that had a short in the coil cable. I told them to give me $50 along with the 12x10 for my 15x12 and I'd fix the 12x10.
Well, that coil had I think two loose wires behind the plug along with 2 or 3 bad pins that somebody over heated and cracked. Didn't have a replacement plug and Radio Shack doesn't carry the right ones, so I bought a plug up there with the same type of pins in it and knocked out the old ones and replaced them.
The fix has lasted for a few years here, but just this evening I noticed at the same site I had hunted the other day at full blast manual sensitivity, that today it was nulling and chattering on me. At first I suspected there was some new EMI in the area and so kept lowering sensitivity and switching bands to judge which might allow a higher sensitivity setting.
Neither did, and it would only get stable and not null when it was almost all the way turned down. Hmmmmm.....So right away I suspected a short in the cable and wiggled it right behind the plug. The thing went bonkers. Knew then I had a short, and it's either my soldering job failed or another pin or two went south on me.
So I unscrewed the plug and looked at the face of it to make sure all the pins where in proper shape, and then re-screwed it back on and tried to finagle the coil cable behind it to give my connections back to normal so I could salvage the hunt.
Well, sometimes it was fine and allowed full blast sensitivity, but other times I had to lower it to about 3PM to calm things down. Worst part is I was hunting in PP and gridding an area, and when I'd hit a target in PP that PP's response told me it was probably NOT iron, I'd flip to disc and get nothing but a null.
I figured I was just wrong about suspecting the target in PP was not iron, as I'm still learning it, so I didn't think nothing of it, until enough of these non-iron-like PP responses I hit still were nulling when I flipped to disc. Still wasn't completely sure, until I dug a few wheats at 6" or so that were breaking up badly like a false coin spike from iron.
Man, a wasted trip. I managed 5 or 6 wheats through all the hassles and maybe an old button (got to clean the crud off it to see), but otherwise I got skunked for 3 hours worth of effort due to the stinking coil fighting me.
So anyway, I'll soon be doing the repair and plan to do a youtube video filming the effort, complete with inspecting pins front and back with an ohm meter while wiggling them to look for cracks inside the plug on them, along with soldering stuff together, and also heat shrinking each wire and then a final large one over them all to hold the cable to the coil plug.
I think this could be useful to people who are new to soldering or fixing coil cables and plugs, as I plan to show how to do all that, and also it should be of help to SEF users who want to know which color wires go to which pins in case they get one that doesn't have a plug on it or something from somebody.
Soldering is easy with a few tricks, and heat shrinking is also cake work even without a heat gun, as you can use a hot hair drier or even a lighter to do that. Want to go over all this stuff in a video because it might be able to help some people, and these questions always seem to crop up.
You can set yourself up with a soldering iron, solder, flux, and some heat shrink tubing from Radio Shack for probably well under $40 or perhaps even under or around $20. Not very expensive to equip yourself for solder work, and for another $4 or so Harbor Tool & Freight has some great "extra hands" in a weighted rig with alligator clips on it and a large magnifying glass to hold things while soldering them together.
I'll cover all that when I do the repair and edit/post the video.
PS- If anybody ever suspects a coil doesn't perform well for them at a site for some odd reason and might be a lousy coil, don't just assume that. Had I not known what to expect from this 12x10 I might have suspected it was just a really bad product. Any time you're not getting very high sensitivity settings in what should be a low EMI environment, or say you seem to be getting a lot of nulling or falsing in certain grounds, don't just assume it's a cheap coil or that that site has a harsh ground matrix or EMI present nearby.
Start at the coil and wiggle the coil cable there, and work your way up the cable while wiggling every few inches until you reach the plug to see if things get better or worse. Chances are if you have a short it's going to be right behind the plug as that's a stress point, but second most common would be right between where the cable leaves the coil and meets the detector shaft where you've started to coil it.
Both points are high stress areas where a coil cable has no length to flex beyond those points, so any movement is like a wave crashing against the shore, so to speak. That's why these two points need to be secured, and without stress being put on the cable right where it meets the coil or the coil cable plug...
