Used vs New: My Experience
I second buying a machine with a good track record. I read every review I could find, over and over. If you are going into the water and work it, the energy and time required to do it correctly is extensive. I think letting the detector become the possible weak link is not a good game plan.
I had bought my very old PI from Kellyco years ago. Now, I had a shot at a used Excalibur 800 and went for it. In hindsight, I'd buy new, and certainly the Kellyco folks have been great offering advice and NOT selling me things that they do not think I need when I asked them about my Excalibur 800 older unit! As it turned out, I had to do some important maintanance on my Excal, as it stopped working and went eratic, and I figured I was in trouble and out the money I spent for the used machine. At that point, I was wishing that I had went with a new detector and Kellyco or another reputable company as a dealer. You can probably find a local dealer too.
I bought a battery tester and checked the newly purchased battery pack NIMH version that I bought on ebay (onlybatterypacks) to see if it was charging to full capacity with the original NICAD trickle charger; It was.
Wow, I was in trouble as I had hoped that the eratic state of the Excal was due to a low battery. Bad battery? Not. I'd recommend "onlybatterypacks" and in fact, just ordered a second battery pack and their quick charger with indicator light on it. I can handle removing the batteries and lubricating the Oring and wanted a backup battery that was ready.
Funny, but when I recieved the used detector, it had a 9 volt square battery in it with some paper towel stuffed in the battery pod. I knew this would be the case going in and from my reading of the manual before the used machine reached me, I assumed that a constant and loud Threshold Sound would occur indicating low battery, and it did. I had a new NIMH battery pack waiting in advance. Bam! Installed, cured, what a deal! It all worked fine along the shore during two outings. All great, that is until I submerged the control box on my first in-water hunt in outing number 3. One dig later, it went crazy! Haywire.
I drove an hour back home really dissapointed and wondering why I tried to save money by buying a roll-of-the-dice used machine. I turned it on and off over the course of two days hoping it would cooperate again. Maybe if I kick it hard??? Yea, maybe I should kick myself! Finally, I disassembled the unit and thought maybe using a blow dryer would remove any possible moisture that had gotten into the electronics compartment. I carefully lubricated the O rings on the caps everywhere also. They were dry for sure. I had to solder a few wires (headphones) that I probably broke in dissassembly! Knowing how something originally went together and having a command of the little tricks makes "proper disassembly" a lot easier and I had no real clue.
OK, I learned alot........I believe that the hex set screws holding the electronics compartment caps in place were perhaps backed in too far allowing some minte leakage. They likely should be threaded in flush with the outer casing surface, and no deeper. I used some electrical tape wrapped around the area where the set screws are located after setting them in flush to further insure that no leakage could occur inside of the battery and electronics pods.
Turned the machine on...........YES! Works great now. But I have not had a chance to water test it. I am nervous. My point is that I am a semi-handy person and an OK trouble shooter. I work on optical instruments and mechanical parts all of the time. But....this potential dead machine was a bummer. Doing it again, I'd support the companies that manufacture these small niche products by buying new if at all possible, and also give my business to the dealers who carry the products and are there for tech support, warranty back up if we need them.
That scare I had made me think: 'Now I must buy a new detector after having bought a used detector.....Damn!!! Why did I do this??'
Buy once. Go with a respected company and a machine with great reviews and a dealer who answers the phone. You'll be wondering if you are crazy once you get in the water and start working. But it's great to be out there in quest of the unknown and every dig is totally unique. I have a suspicion my purchases will pay off in finds, and get me out of doors in peaceful and beautiful places that I normally would not have gone to.
I just would recommend that you buy one detector, not a cheap off brand unit that causes frustration, and then a better well reviewed model. I want to also say that I am not afiliated with Kellyco or any manufacturer. Good luck