Destroying the HF9FMD to Build a Beep-n-Dig Brute

USAFSSK

Junior Member
Joined
Jan 4, 2014
Messages
38
Location
Mississippi Gulf Coast
I've been happily swinging the Discovery 3300 for many years, and it has proven itself time and again as an EXCELLENT coin shooter. That being said, it has made me a lazy detectorist. I can rake in clad all day long, when I only dig solid, repeatable identifications. The Target ID is reliable, the entire unit is very light, and it doesn't do too bad on batteries. However, I KNOW I'm passing up better targets, simply by my lack of digging them. The 3300 is quick to tell you that everything that isn't a coin, is junk. It doesn't take long to convince yourself of this, when clad is so reliable, and frankly, it's money. I have ventured into the water with it a few times, but the fear of damaging it makes the experience less than stellar.

It's worry-free, get wet, beep and dig time (on the cheap).

There's a 'new' model/version number of the Harbor Freight 9 Function Metal Detector on the shelves. My local store had one each of the new and previous versions on the shelf. The older model is the 67378, as its 'user manual' is dated 2009. I picked up the 62307, which is dated either 2013 or 2014, I can't find where I put the manual and HF hasn't updated the web with the new model's info. I should have bought them both, but I'm a cheapskate and was using my 25%-off coupon to pick one up for $33. I may still go back for the other, just to destroy it for the sake of circuit card and other internal comparison pictures, but after I get another coupon.

The plan goes something like this...

DIY straight shaft.
Plano waterproof box.
Plasti-dip or similar coil coating.
Remote power and pinpoint switches on hand grip.
Vibrate and/or light in place of sound & 'signal strength meter'

It will be a close cousin to TCosbyJr's franken-detector but purpose built for shallow water submersion.

I've started hitting the thrift stores and flea markets searching for an old set of arm crutches with no success as of yet. I found that KellyCo has 'Bounty Hunter Lower Shafts' on sale right now for $10 a piece. With that, I may just grab the first appropriately-sized aluminum tubing I come across. I haven't bought the lower shaft yet as I just can't swallow $16 to ship what should only cost about $4. I guess I need to find more things to buy from KellyCo :P

Pics to follow soon, the 'net is being slow to upload today, and I've just been summoned by my bride to go out of town, which includes more 3300 swinging time (boohoo). I wouldn't normally start with such an incomplete initial post on a new thread, but if I don't save now, I'll have forgotten most of what I've already said. I'm sure no one here can relate to that ;)
 
Good luck! I've seen a few serious mods done to this detector and it was the one I started with and still have sitting around. I might hack mine someday when other projects get completed.

Just know that there may be nothing different with the new model. They change model numbers when a different factory produces the product. You'll see that a lot on their power tools.

Papa
 
Aluminum crutches are $5 a pair from most St.Vincent De Paul thrift stores. Many times you don't need a lower shaft as you can simply drill a hole at the end of the crutch for the coil fastener. Alt is using a Mop handle, Paint roller extension, or Snow-ski pole.

Plano boxes work great....as I've had one for a year and working on my second ML waterproof Explorer.

An alternate to w/p headphones or lights is to use an earbone / vibratory buzzer. These are easily waterproofed and can be mounted to the handle so that you can feel the signal and be free of cumbersome wires. Additionally, some people have gone the route of wireless headphones with the transmitter inside the plano box -- this works but puts your speakers at risk of water damage.

http://metaldetectingforum.com/showthread.php?t=88982&highlight=behold+sovzilla Is a link to most of the setups I just listed above. Any other questions, just ask! :grin:

-David
 
Aluminum crutches are $5 a pair from most St.Vincent De Paul thrift stores. Many times you don't need a lower shaft as you can simply drill a hole at the end of the crutch for the coil fastener. Alt is using a Mop handle, Paint roller extension, or Snow-ski pole.

I wasn't sure if I wanted the aluminum pole right on top of the coil or not, for interference issues. I have been looking at the aluminum paint roller handles as a potential option, too.

Plano boxes work great....as I've had one for a year and working on my second ML waterproof Explorer.

I've seen so many have good success with them, and I figure since I'll only have one penetration to worry about for the coil wire, a dab of dielectric grease on the o-ring should give me a good service life.

An alternate to w/p headphones or lights is to use an earbone / vibratory buzzer. These are easily waterproofed and can be mounted to the handle so that you can feel the signal and be free of cumbersome wires. Additionally, some people have gone the route of wireless headphones with the transmitter inside the plano box -- this works but puts your speakers at risk of water damage.

I just learned about the earbone deelio's just the other day on a random 'underwater + buzzer' search. If I find I really enjoy snorkeling while detecting, this would really be cool.

http://metaldetectingforum.com/showthread.php?t=88982&highlight=behold+sovzilla Is a link to most of the setups I just listed above. Any other questions, just ask! :grin:

Wow, with all the searching I've been doing (google searching using "site:www. metaldetectingforum.com") I don't think I've run across that yet, looks awesome! I peeked at the cable clams at the local West Marine, just not convinced I'm ready to pull the trigger on them yet.

-David

Well here's where I'm at so far in the dis-assembly of the HF9FMD:
1Z5Bo9pl.jpg


The little handle with the button gave me fits!

Does anyone know what type of signal feeds the meter? I haven't broken out the multimeter yet. I'm guessing it's just a voltage feed? If I delete it (which I would like to do) I wonder if I can simply delete it, bridge it, or need something in its place like a light bulb, or maybe the vibrator motor?

For such a small coil, it sure is heavy. Almost disappointingly so.
 
Coil Wires

So after taking a photo so as not to rely on memory, I have cut the coil wire from the board to see what's inside the insulation jacket. Looks like the TX pair and RX pair are individually shielded with foil, along with a bare Gnd wire, that at this point may, or may not run all the way to the coil. For me, atleast, cutting the cable near the board is without fear, but cutting near the coil... not until I know I can open the coil without destroying it.
JF14pddl.jpg

3hrYqfbl.jpg



Is there anything I need to check and record other than resistance values for the coil through the terminal ends of the wires? I don't yet know (understand) how to check inductance, but here's where the resistances fall:
t4QLczil.jpg
0DSlM3Vl.jpg


Any quick guesstimates on which is TX and which is RX?

*edit: On a side note, I know what I need to add to my KellyCo shopping cart now, a new coil for my 3300 :(
I knew I got some water intrusion a few weekends ago on my last wading trip, but when I took it to Gulf Shores yesterday for some dry sand beach beeping, I was all over the map. Every time you touch the coil wire near the coil, it would throw false readings and/or power down. That's what I get for believing that a "waterproof coil" was waterproof. :roll:
 
has anyone seen one model be any better than the other as far as the new or old HF9 product number?
 
So after taking a photo so as not to rely on memory, I have cut the coil wire from the board to see what's inside the insulation jacket. Looks like the TX pair and RX pair are individually shielded with foil, along with a bare Gnd wire, that at this point may, or may not run all the way to the coil. For me, atleast, cutting the cable near the board is without fear, but cutting near the coil... not until I know I can open the coil without destroying it.

Is there anything I need to check and record other than resistance values for the coil through the terminal ends of the wires? I don't yet know (understand) how to check inductance, but here's where the resistances fall:

Any quick guesstimates on which is TX and which is RX?

There is a book called "inside the metal detector" by George Overton, That might help you out.

https://www.amazon.com/Inside-Metal-Detector-George-Overton/dp/0985834218
 
Curious to see how this ended up, I did a similar mod to my BH IV a few years back. Actually just further modded it the other day, might drag my old thread back up with some updated photos. Nothing that I would use everyday, but I made it water resistant and its a solid backup detector if I have a new person hunting with me. Keep us posted!
 
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