Cen Tech Clamp Meter Buzzer Goes Off Continuously
Problems with your Harbor Freight Cen-tech pinpointer? How to fix em.
- Thread starter kimsdad
- Start date
- #1
I'm posting this in case anyone out there purchased a Centech hand held metal detector from Harbor Freight for use as a pinpointer and is having problems with it. I bought one last year and I'm really pleased with what I got for my $16.95. I have a Sunray probe on my SE, but I still use the Centech to really narrow down those small targets, and it's the only pinpointer I use when I'm hunting with the DFX. I really beat the snot out of this pinpointer. 
I've lost it in the woods over a real rainy night and it still worked when I found it again the next day and dried it out. I've hunted in powder-fine dust, and plunged it almost up the the box in mud water. I've pushed it into the mud and soft dirt and twisted and pried dirt with it. Since it was so cheap, I've treated it with little respect. What surprises me is just how easily it bounces back from all this abuse.
Over the course of this abuse, I've found that there are a few things that gave me problems. I was able to fix these, and I wanted to pass this info on so anyone else who isn't afraid to dig into it so they deal with them too.
First of all, I'm not looking for "Buy a real pinpointer and you won't have to deal with these things" replies. I get that. I don't want to buy a "real pinpointer". I'm more than happy to spend my hard earned clad on extra coils and other things like that. 
Secondly, if you decide to try these remedies, you do so at your own risk. I make no claims that any of this is completely safe. There are risks in anything we do, and this is no exception. You could ruin your $16.95 pinpointer or hurt yourself while trying to fix it. Rubbing alcohol is flamable. Don't use it by a flame or heat source. Again, you assume any and all risks.
Third, before performing any maintenance on the unit, remove the battery.That said, there are four things that gave me problems
That dirty rotten switch... 
This was the first thing that I had trouble with on this unit. After several hunts in the dust, the switch got dirty and would only operate intermittently. It's not a sealed switch, so dust and moisture will get in it and cause problems. Not a big deal, the switch can be cleaned. After taking the battery out, open the unit by removing the four screws holding the back on. They are small screws, but can be turned with a 3/32" Phillips screwdriver from a precision screwdriver set. Carefully pull the back off, being careful not to pull it apart too much so you don't pull the wires to the speaker out.
Hold the unit so the switch is facing down. Put a folded paper towel under the switch. Apply drops of ordinary rubbing alcohol to the back of the switch where the contacts enter the case and start pushing the switch up and down on the paper towel. You should see the alcohol work its way into the switch through the gaps where the contacts go into the case. If the switch is dirty, you'll start to see dirt and gunk flow down around the red button and onto the paper towel as you work the switch. This dirt was fouling the switch. Keep doing this over clean sections of paper towel, adding more drops of alcohol until no more dirt comes out. Once it is clean, keep working and shaking the switch without adding more alcohol. This will help get the excess out. Then just let the whole thing sit out for a while to dry before reassembling it.
My switch gunks up a lot, so to make cleaning easier, soldered wire extensions on the switch and insulated the connections with heat shrink tubing. This makes it easier to clean the switch without having to deal with holding the pinpointer case. I simple remove the switch from the case and clean it as explained above. One of these days, if I come across a cheap sealed switch, I just might install it.
Hey, the tip isn't waterproof!
The tip of this unit is press-fit into place. It isn't waterproof. I waterproofed mine by gently prying off the tip, being careful not to break the coil wires. The coil is glued to the inside of the tip of the probe, so if you pull the tip too far, you might break the wires. Clean both surfaces with rubbing alcohol, let them dry, and apply a coating of silicone caulk to the part of the tip that fits in the probe. Press the tip back into place and wipe off all excess silicone. Allow it to cure for at least 24 hours. Now your tip should be waterproof.
My probe is loose!
Only after months of abuse, the screw holding the end of the probe to the inside of the case wore through the inside of the case and was loose. Simply replace this screw with a small bolt, lock washer, and nut. Just be sure the head of the bolt is bigger than the hole in the back of the cast that the original bolt fit into. Use a washer under the bolt head if it isn't.
Hey, there's gunk in the speaker.
One other thing I noticed. The speaker hole kept getting gunked up and the screen eventually tore. After cleaning the case, I covered the hole with a piece of blue masking tape. It keeps dirt out and you can still hear the beep.
This unit can be easily modified by anyone with electronics knowledge. It can be made to vibrate with an add-on vibrating motor, or a "target found" LED can be added.
Eagle77 has a great post of one of these mods here:
http://forum.treasurenet.com/index.php/topic,178515.0.html
I hope someone finds this post useful.
HH!
- Jun 11, 2004
- 1,683
- 68
- Hurlock, Maryland
- Detector(s) used
- XP Deus, Excalibur II
- Primary Interest:
- All Treasure Hunting
- #2
Alcohol will leave bare contacts that will be susceptible to corrosion. It would be better to clean with a switch cleaner with lubricant, available from Radio shack. It is also good on open potentiometers.
But they way you treat that pin pointer you may want to just get another one any way.
Ed D.
- Thread Starter
- Thread starter
- #3
But they way you treat that pin pointer you may want to just get another one any way.
Ed D.
I think you got it.
The idea of my post is to help anyone that has one of these that has a gunked up switch. They can give new life fast to it and use it again, instead of throwing the whole thing away. We're not talking about a fine piece of audio equipment here after all. I've cleaned this switch several times and once the dirt is out, it works like new. I want bare contacts for good conductivity and nothing left behind to catch more dust. Besides, if I ever kill the switch, I'll just throw a new one on! 
Repair + reuse = recycle. 
- May 22, 2005
- 7,205
- 58
- Primary Interest:
- Other
- #4
kimsdad,
outstanding post. 
Think a lot of folks went with the Cen-tech.
Use a Sunray with my 1500 but use the
Cen-tech when Im using the De Leon.
Don't think you can beat it for the money.
Thanks for the tips. Have them bookmarked.
have a good un..................
SHERMANVILLE
- Jun 11, 2004
- 1,683
- 68
- Hurlock, Maryland
- Detector(s) used
- XP Deus, Excalibur II
- Primary Interest:
- All Treasure Hunting
- #5
Kimsdad,
How long did it take for you to get that pinpointer looking like that? I also have a Whites Bullseye that I use all the time and it does not look that bad. I even carry it in my pouch with trash. Do you clean your detector (exterior)? Please follow up when/if the pinpointer gives up the ghost. You would be a good gauge for how long the Centech can last. I see your point on a lubricating cleaner, but maybe a simple contact cleaner will suffice.
Ed D.
- Sep 27, 2007
- 2,941
- 53
- Sal Sagev Adaven
- Detector(s) used
- E-TRAC,,,, SOVEREIGN GT,,,, GP 3500,,,,
GB PRO.
- Primary Interest:
- Metal Detecting
- #6
Awsome post Kimsdad , thanks
- Thread Starter
- Thread starter
- #7
Thanks, Shermanville!SHERMANVILLE ILLINOIS said:kimsdad,
outstanding post.
have a good un..................
SHERMANVILLE
Kimsdad,
How long did it take for you to get that pinpointer looking like that? I also have a Whites Bullseye that I use all the time and it does not look that bad. I even carry it in my pouch with trash. Do you clean your detector (exterior)? Please follow up when/if the pinpointer gives up the ghost. You would be a good gauge for how long the Centech. I see your point on a lubricating cleaner, but maybe a simple contact cleaner will suffice.
Ed D.
Hi Ed. Yes, I clean my detector - LOL! I wipe the pinpointer down after a real dirty hunt too, usually with paper towels and either a little water or alcohol. I hunt in the woods a lot, especially this time of year when it's not cool to dig in turf due to our weather and worries of damaging the grass. This means I'm slogging through the mud, and pulling both finds and trash from mudwater filled holes. Last hunt out was so muddy that after a while I couldn't read the SE screen. Thank goodness for the head cover! There's a pic of it in this post.
http://forum.treasurenet.com/index.php/topic,220654.0.html
That dirt is from my gloves, so you can tell there is mud everywhere. Last year I was able to hunt 3-5 days a week some weeks, depending on the weather. Many hunts were 6 hours long or longer. That pinpointer has seen a lot of use. It's a working pinpointer! If I paid $50 or more for it, I'd probably take better care of it. Since I only paid $16.95, I think it's already paid for itself. Does it really look that bad? I'll post an update if it ever dies for good.
You're welcome Extractor, and thanks!Awsome post Kimsdad , thanks
- #8
I bought one of these this last weekend as a stop gap until I can justify the DX-1, it works very well! I soldered in a vibrating motor and disconnected the buzzer, took 5 minutes and some superglue! Now it is no longer so annoying... After playing around with it, I think it will work great!!
- #9
I've just seen this post for the first time so I hope Kimsdad is still checking in on it. I have a CT PP with switch problems. The way you said to fix it and the pics looked easy enough but how easy is it for someone electronically challenged like myself. I've done a few things with wires but very minimal.
- Apr 26, 2010
- 558
- 69
- NC
- Detector(s) used
- Garrett AT-Pro & White's TDI & Tesoro Compass uMax
- Primary Interest:
- Relic Hunting
- #10
Has anyone tried the rubberized tool handle dop/spray-on coating on the probe in an attemp to waterproof it?
HH
Dwight
- Jun 11, 2004
- 1,683
- 68
- Hurlock, Maryland
- Detector(s) used
- XP Deus, Excalibur II
- Primary Interest:
- All Treasure Hunting
- #11
The problem with just sealing around the probe is it is not the only point water can enter. The case, adjustment pot. and switch are others.
Ed D.
- #12
Thanks for the tips! In my experience my CT pinpointer out performs my Whites. Here's how I modified mine:
I took some cheap Harbor Freight heat shrink and put it over the last inch and crown of the probe to keep the cap on and cut down on wear at the edge of the cap.
There was a fairly large gap between the sensitivity knob and the body so I put more heat shrink over that. It didn't waterproof it but it's kept most of the dust/dirt out.
Gary
- Mar 24, 2010
- 1,451
- 506
- Minnesota
- 🏆 Honorable Mentions:
- 1
- Detector(s) used
- Minelab Equinox 800, Minelab SE PRO, Garrett AT Pro, Garrett Ace 250
- Primary Interest:
- All Treasure Hunting
- #13
I finally got mine in the mail after being back ordered for a few weeks.
I put the battery in, pressed the on button and got a loud tone. The problem is that the tone never goes away and never changes even when you put the probe near metal OR when I adjust the sensitivity 
Anyone else have this problem or is mine just broken 
- Mar 28, 2008
- 1,360
- 32
- Aloha, Orygun
- Detector(s) used
- wishing stick
- Primary Interest:
- Other
- #14
WIT -
You must have gotten the one I sent back. LOL
There was a thread on here last year about adjusting the internal pot.
(The one on the circuit board)
Grey
- Jun 11, 2004
- 1,683
- 68
- Hurlock, Maryland
- Detector(s) used
- XP Deus, Excalibur II
- Primary Interest:
- All Treasure Hunting
- #15
WIT,
Not to be rude or condescending(?), but the unit does have an adjustment knob. Directions are to turn until sound stops. I think it might be a voltage adjust or gain adjust. Have you tried this. If so I would return it.
Ed D.
- Feb 18, 2010
- 7,393
- 2,648
- Vancouver WA
- 🏆 Honorable Mentions:
- 1
- Detector(s) used
- Chug)Whites Classic 5 ID, (Red Whites Coin master Pro)
Chug and Reds New Additions
Give It Up>> Garrett's AT Pro
Buttercup>> Garrett's Ace 250
Show Me the Money>> Garrets Ace 400
- Primary Interest:
- Metal Detecting
- Mar 28, 2008
- 1,360
- 32
- Aloha, Orygun
- Detector(s) used
- wishing stick
- Primary Interest:
- Other
- #17
B2D - I got a unit where the external adjustment wheel would not go far enough.
This is controlled by the internal potentiometer on the circuit board itself.
That adjusts the range the external wheel can affect.
Also I found that pointing the unit up or down makes a difference when adjusting external wheel.
Grey
- #18
I put in a new rocker switch (non momentary) so I just leave mine on now when I hunt... I accidentally burned out the led and it seems to detect further now
Then I used clear silicone and totally sealed up all the openings and case so it not longer gets dirty, it looks like hell but it sure can take some abuse now!
- #19
Are you hunting nuggets with it, and how small a mass will it pick up?
- Mar 24, 2010
- 1,451
- 506
- Minnesota
- 🏆 Honorable Mentions:
- 1
- Detector(s) used
- Minelab Equinox 800, Minelab SE PRO, Garrett AT Pro, Garrett Ace 250
- Primary Interest:
- All Treasure Hunting
- #20
WIT -
You must have gotten the one I sent back. LOLThere was a thread on here last year about adjusting the internal pot.
(The one on the circuit board)Grey
I'd like to see that thread. I missed my window for sending it back but I'll fix it someday I guess.
WIT,Not to be rude or condescending(?), but the unit does have an adjustment knob. Directions are to turn until sound stops. I think it might be a voltage adjust or gain adjust. Have you tried this. If so I would return it.
Ed D.
No worries, you can't offend me
But yes, I know about adjusting them with the knob. It was defective from the beginning.
The sad thing is that I just had to return a White's TX-2000 because it had the same problem, then it was replaced by the seller who admitted it was defective. Now I have a new one and I think it's horrible. I'm returning this one as well and buy a real one. 
Thanks though!
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Source: https://www.treasurenet.com/threads/problems-with-your-harbor-freight-cen-tech-pinpointer-how-to-fix-em.118040/
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