They have had over 25 years to waterproof the control box......its a very old design,not a new detector.It's like their 1220xd,a none motion machine that has been in production for 30+ years and still sells well.....i have one.
The 4 has its roots in Eric Fosters pi designs,i'm sure that has something to do with its "supposed" excellent performance.I suppose that while it still sells well they don't think it necessary to improve it??
Seems a lot of the older PI's were based on Eric Fosters designs, that man left his fingerprints on a lot of different detectors, lol. I am by no means qualified to judge or evaluate PI designs, just got my first PI last year after 56 years swinging BBS/SMF, VLF, TR, and BFO detectors, but from what I've seen and have heard, PI circuits tend to be fairly simple, smaller and less complicated than today's modern SMF digital detectors, at least for the White's Surfmaster PI series. My Dual Field has 3 control knobs, the previous PI versions only had 2 control knobs to adjust, so a fairly simple circuit. After the Dual Field, White's released the BeachHunter PI, which has a larger control box, with about 5 or 6 control knobs, and from what I've read, it's basically a TDI SL put into a waterproof enclosure. So, I figure the circuit for the BH is probably more complicated than my Dual Field since it has more adjustment possibilities, but still probably simpler than today's digital circuits.
I hope to learn a lot more about PI's as my wife got me Carl Mooreland's "Inside the Metal Detector" 3rd edition book for Christmas. Carl is a master/genius PI designer and was involved in the design of White's Surfmaster PI's as well as the TDI SL I believe. The book is large with 612 pages, so I'm sure it's going to melt my brain. Carl's probably forgotten more about detector circuits than most of us will ever know, lol.
Just for grins, I posted a capture of my Dual Fields control box. You can see that the box itself isn't that big. I just measured mine and it's 4" wide by 6 & 1/2" long. As you can see in the pic, after removing the top lid, 1/2 of the area inside the box is for the batteries, leaving the other half of the box for the pcb. Based on the size of 4"x6.5", that would only allow a maximum of 4"x3.25" for the pcb, but more likely a bit less than that to allow for the thickness of the box, room to position the pcb and to run wires, etc., so the pcb is probably very small. The pcb is covered so I'm not going to mess with it, but I'd love to take a look at the circuit board. There can't be that many analog components on that small of a pcb, so I assume that the circuit of my Dual Field probably isn't that complex, compared to today's detectors & electronics.
