Good news, I think! But first some initial bad news...
With Kered's last bit of technical info to double confirm my coil pin outs and specs, I decided it was time to see if indeed there was a problem with this coil and fire it up on my GT. Like I said, I had tested the pins at the face of the plug and at the solder points at the back for the wires. All looked well, so I was a little disappointed that I didn't see an obvious problem like a broken solder joint to fix. Everything checked out with an ohm meter, and that even involved doing a little wiggling of each pin/wire while checking them with it to make sure there wasn't a short that only showed up here and there.
Anyway, threw the coil on my GT but didn't heat shrink any of the exposed wiring at the back of the connector yet. A good tech never assumes there is no problem and puts everything back together with out running the device through some powered up testing first. I carefully made sure none of the wires was in danger of shorting to another with the lack of heat shrink and powered the GT up.
I get a lot of RF noise in my garage so I headed for the back yard but the unit was still falsing. That's not unusual because any of my coils run unstable in my backyard unless I lower sensitivity all the way in manual, which seems more stable than Auto when it's this bad, although Auto some times works better than lowest manual, probably due to the changing RF noise for that particular day.
Threw it into it's lowest manual setting and she calmed right down. Good so far. Swept around a few minutes and all seems well, with no instability or static that might indicate a problem exists. Now for the acid test. Started wiggling the cord from down near where it enters the coil and made my way up the cable with my hand, wiggling it in various spots as I went. All was well I thought until I got up near the connector. Instantly the GT started falsing badly. Hmmmm....Took my hand away and things got stable. Put my hand back on the wire near the connector and once again it's going nuts.
OK, obviously there's a short I missed with initial work bench testing. In a way I was very happy to see that, because I would have been suspicious and miffed if I couldn't find a reason for the prior owner's experience with static and unstable operation. Glad I didn't heat shrink everything back up yet at the connector. Off to the garage I go and start doing more intense ohm meter testing and stressing the wires/pins in various places near the connector to try to register any drastic changes in ohm readings with my meter. Well, after I had already checked three of the pins/wires and found nothing I was starting to think that it might be a short in the cable a few inches from the connector or something, so I'd need to probably start all over and check each one again. Still, I had the final pin to check, which was the black wire (pin 1).
Starting wiggling that pin and the wire in various spots when the pin broke off right at the surface of the black plug enclosure. I was barely putting any pressure on it so I knew right away it shouldn't have snapped like that and I had found the problem! On closer inspection under a loop I could see that this pin had obviously been overheated either in manufacturing or in repair and had caused the problem. There surface of the pin where the break was was very black to indicate it had been way overheating. Either somebody used a propane torch to do their soldering (which I do on occasion when I'm working on something big that needs a lot of heat), or they had used a really high wattage soldering iron. These pins are very thing and so don't have much ability to bleed off heat if they are really torched.
Off I got to Radio Shack in the hopes of another 6 pin plug, because where this one broke right at the surface of the black part of the plug wouldn't be easy to solder. No luck, Radio Shack only had an 8 pin plug in one of the parts drawers and it's pin holes wouldn't match up to mine. I still bought that plug because it had the same types of pins in it. When I got home I took a needle and pushed the rest of the bad pin out of that hole, pulled a pin out of the 8 pin plug, and then tapped it with a hammer in place into the old plug. Done!
Well, I thought I was done. In the process of tapping that pin in place one of the other pins fell apart in the same place. Now I really know somebody blasted this thing with too much heat, because there is no way I even touched that pin when tapping this new one in. Once again under a loop I could see that it was overly heated right at the surface of that plug. OK, let's really push hard on the rest of these suckers and see if any give. The rest were fine, so I tapped another pin in place on this other one two.
Soldered those wires back to the pins, heat shrinked each individual wire and put to isolate them from each other, then slid one big piece of heat shrink tubing over all of them and heated that up to secure things better. Slid the connector's metal outer casing back into place and put that back together, then slid yet another bigger piece of heat shrink tubing over the back side of the metal casing and shrunk that down with my heat gun. Factory finish back in place with no one the wiser. Let's see if it works, as there could be another short elsewhere.
Off to the backyard again and everything is stable. Wiggle the wire once again at the coil, working my way up to the connector. Get to the connector and hold my breath. Still fine! Now all I have to do is head out in the field and confirm all really is well, because I had this thing at lowest sensitivity due to the usual RF noise in my backyard. Once I tweak out sensitivity to something super high any random short in the cable will become much more apparent as it should cause the threshold to go wacky or static to appear. That's also the only well I'm know for sure if there isn't internally wrong with this coil, but by the looks of it I've got her fixed!
First rule we learned in HVAC school- Most problems are electrical. Second rule- Most electrical problems are not due to failed components, but rather due to bad connectors, shorts, or carbon build up on contact points. That's something to keep in mind when and if you ever have a problem with your detector. Take it apart (if it's not under warranty) and inspect all the components with a loop, looking for any hair line cracks in solder points and such. Wiggle parts as you go. That's also a good way to see if something will work (not much risk of shock in a detector, but just the same use a wooden tool so you don't short anything). Often if you wiggle in the right place you might be surprised to have it come back to life.
Off I got to the park to see what gives with this thing! By the way, when I was swinging it around in the backyard for the first time it was obvious that this coil is much lighter than the 15x12, not that that coil was too bad with the coil cover off. Lighter than the stock 10" coil with cover still on, in fact by I think .6 oz. Regardless, with no cover on this 12x10 it felt even lighter, and even much lighter than the stock 10" coil. I won't know for sure until I get my digital scale back and weigh it with and without coil cover, then add that to the coil weight chart I posted for people. I can say that my light weight GT feels even lighter to me than my Whites I've owned in the past. I'm probably about 4 pounds 2 ounces or so now by doing the math in my head.
Anyway, this coil like the 15x12 just looks and feels mean! And even with this coil my very brief initial impression is that I feel like I'm sweeping something with much better coverage than the stock 10" coil around, just like I did with the 15x12. I'm excited to explore it's potential in both depth, stability, and separation compared to my 10" Tornado stock coil. Off I go...
