Modified Harbor Freight Pinpointer w/ pics

I get the idea that it is fun to mess around and try to modify and fix things, I have done it myself.....but gee whiz all this for a $15 pinpointer! I got one because they were on sale and had a discount coupon, I got it because my wife started to metal detect with me using my old Ace 250 well after a few uses the button stopped working so I tinkered with it and fixed it but it was so hard for her to use...setting sensitivity etc I got her a Garrett Pro Pointer too. It is one thing to have fun tinkering but if I am out spending time detecting I want something I can count on. No offence intended to anyone who uses the Cen Tech and it is better than nothing.
 
most of the problems with the cen tec's was the power button, a 3 dollar fix and its perfect, the vibrating motor was just me tinkering cause i didn't want the unwanted attention of the loud beeping. that cen tec was the best 20 (with mods) bucks i ever spent. and if i lose it in the woods i'm not out 125 bucks
 
Yep, the cheapest fix I had for that darn speaker was a 1" square for duct tape. Covers the hole and muffles the noise to faint sound. And it peels off if you want it to be louder. Mine works great for the price and after a little tinkering Hope everyone has a Merry Christmas!
 
I went to Rat Shack Saturday.. when I got there they didn't have one but offered to order it for me.. I passed on that. I took the motor out of an old tracfone that I had. I modded the pinpointer.. working good. I turned up the depth on the pinpointer but turned it back down to where it picked up a coin at about 2". I also put the pinpointer in a zip lock bag and and tape it to where it conforms to the shape of the pinpointer it keeps everything clean except the tip..
 
It's the Switch

LOL that's funny I just did this too and Hadn't seen yours...I think that push button switch needs to be removed as it IS the WEAK LINK. If one were to just replace that push button momentary switch with a toggle or momentar toggle it would be much better. I posted a video on you tube at http://www.youtube.com/watch?v=5seiLHyNbjw and you can take a look at my blog at http://www.treasurebone.blogspot.com for a detailed written tutorial with photo's. Not trying to hi-jack this post just adding what I learned from my experience.
 
LOL that's funny I just did this too and Hadn't seen yours...I think that push button switch needs to be removed as it IS the WEAK LINK. If one were to just replace that push button momentary switch with a toggle or momentar toggle it would be much better. I posted a video on you tube at http://www.youtube.com/watch?v=5seiLHyNbjw and you can take a look at my blog at http://www.treasurebone.blogspot.com for a detailed written tutorial with photo's. Not trying to hi-jack this post just adding what I learned from my experience.

I watched your video on youtube. it was rather amusing as well. do you have to use that specific switch from radio shack or can you use any toggle switch (ex: one you may find at a auto parts store)? i think if i do that mod i'll just do the switch instead of getting into the motor thing too. i've heard some people on here increasing the depth they are able to pick up with the cen-tech. have you ever heard anything about that?
 
I watched your video on youtube. it was rather amusing as well. do you have to use that specific switch from radio shack or can you use any toggle switch (ex: one you may find at a auto parts store)? i think if i do that mod i'll just do the switch instead of getting into the motor thing too. i've heard some people on here increasing the depth they are able to pick up with the cen-tech. have you ever heard anything about that?

i've increased the depth on mine but it takes a little messin with, you have to open the unit up and locate the sensitivity pot (it has a tiny screw on it) then give that tiny screw a 1/4 turn clockwise, make sure your external sensitivity knob isn't turned all the way down or the unit will keep beeping and you won't be able to stop it, it takes alittle bit of messin with but you can gain an extra inch or two
 
i've increased the depth on mine but it takes a little messin with, you have to open the unit up and locate the sensitivity pot (it has a tiny screw on it) then give that tiny screw a 1/4 turn clockwise, make sure your external sensitivity knob isn't turned all the way down or the unit will keep beeping and you won't be able to stop it, it takes alittle bit of messin with but you can gain an extra inch or two

that's not a bad increase at all. you keep mentioning a sensitivity "pot". what's a "pot"? is that short for something? is it pretty easy to recognize once you have case apart?
 
once you remove the 4 outside screws on the back of the case (do not remove the screw in the center of the back of the case, that holds the probe tight) anyway once ya open it up look for this......its the little blue box with a tiny screw on the top, my screwdriver is pointing to it
 

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i added a micro vibrating motor to mine which i put on the opposite side of the case and held it there with the sticky side of velcro (holds better than tape), i also changed out the power button
 

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thanks for the pics dogpound! that will certainly help. the vibrating motor seems like too much for me to mess with. i'm bound to screw something up if i add that. i understand a lot of forum members just tape over the speaker holes which i guess would also serve the purpose of keeping dirt out of the case.
 
tape will also quiet it down for those public areas(i did the same with my garrett propointer plus it keep dirt and grime out) on the centec i don't use the speaker so i just cut the wires so mine only vibrates. for a 16 dollar pinpointer and less than 10 bucks in mods. ya really can't beat these.....plus it was something to tinker with since i can't seem to leave anything alone:lol:
 
tape will also quiet it down for those public areas(i did the same with my garrett propointer plus it keep dirt and grime out) on the centec i don't use the speaker so i just cut the wires so mine only vibrates. for a 16 dollar pinpointer and less than 10 bucks in mods. ya really can't beat these.....plus it was something to tinker with since i can't seem to leave anything alone:lol:

is that the new switch that is in the picture above? or is that still the stock one from centech? a push button type would be ideal i would think so you aren't accidently flipping the toggle switch on/off when putting it in a pocket/holster.
 
is that the new switch that is in the picture above? or is that still the stock one from centech? a push button type would be ideal i would think so you aren't accidently flipping the toggle switch on/off when putting it in a pocket/holster.

the one in the pic is the new switch, must be held in (just like the old switch) to work, the new one seems better sealed.
 
I just want to thank all those that had input and the knowledge to do this. I took the plunge and modded mine. I connected the motor to the transistor instead of the speaker on mine. I replaced the switch with one that was similar from RS and i just had to shave the hole a little for it to fit together tightly. Again for the price of this PP you cant beat it for someone that is just starting out. Duct tape works great over the speaker to quiet it down. I hunt a tot lot that is maybe 100 yards from a house and it quiets it down really good. Too bad i dont use headphones on my machine or i would be really quiet.
 
I just received my HF PP in the mail and noticed this - yes, it has a temperature stability issue. This is likely to do with the Op-Amp used but I'm not sure until I completely reverse engineer it and make a schematic (which I will eventually do, for now I only have a parts list generated, haven't removed the PCB to make schematic yet.).

My goal is to make the buzzer volume depend on distance to the target which should be totally doable with a few extra parts.

I suggest adjusting the internal variable resistor (VR1) until it stops beeping when set to 50% on the external VR and no metal around. Do this at the median temperature you operate at.

Has anyone had problems using the HF detector in the heat?? If it gets about 100deg. it will not shut up!! Anybody else have this problem?? I havent done any mods to it yet. Another thing, sometimes when it is working right, if I turn the shaft towards the ground ie. upside down it goes off also(no metal around) almost as if something is loose and moving inside...... Any help or ideas???

EDIT- Ok, I tested out my theory.
1. Put a mark on sensitivity knob at the point it wouldnt beep
2. Put the detector in the sun and got it warm
3. Try it out in same spot and it beeps like crazy until I turn sensitivity knob way down.
4. Put on A/C vent to cool it down and now I can turn the sensitivity knob alot higher than in step #1

To sum it all up heat has a very negative effect on this detector, guess I have to bring a cooler with me! :)
Anyone else have this problem with any other brand of PP? Or is it just the HF one? Or just mine lol
 
There is actually a spot on the board for a DPDT switch marked BZ and MOT - the BZ is soldered closed so it is always in this mode.

I haven't reverse-engineered the schematic yet (but will eventually) but I suspect this diverts power from the Buzzer to the MOT pinout. Simple enough to test with a VOM/Multi Meter.

Billvert,

Yeah, I noticed the motor markings on the PCB as well. I don't know of another Centech pointer. My guess is that maybe there is another model and they get rebranded with these features added.

Good idea with adding the DPDT switch! As you know, there is limited space in the case however I am sure Mouser will have something that fits, maybe check Digikey or Jameco as well.

My next project was to work on increasing the range of the pointer but I just haven't had any time to work on it. I was going to try and wire a new coil however the coil in the wand is currently firmly in place with epoxy. The wires are so small I am not sure how to remove it without damaging it or melting the coating on the wires. Even if I got it apart, it would be hard to make a better coil then the one already in place. Takes alot of skill, practice and patience to make a coil. Maybe someone else has tried this or has experience in this area?

Good luck with the mods!

maddog
 
Would painting it white help to cut down the heat issue by not absorbing as much heat from the sun? Maybe a white pouch for it too?

Just a thought from one who knows absolutely nothing about electronics and mods...

Later,
Brian
 
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