broken (?) Cen-Tec (HF) pin pointers

ryanw95

New Member
Joined
Feb 11, 2021
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9
Location
Meridian, ID
Gang,

I have a set of these that are displaying the same symptoms, both don't beep at metal no mater what the sensitivity is set at with coins next to the tip. LED is on when I depress the button. Found them in my box of detector stuff the other day and thought I'd see if they still work. They are of the 2012 vintage according to the sticker on the back.

Any idea of where to start? I tested the speaker and that works fine.

I haven't played around with electronics for a while so I'm rusty on things to check. Maybe the sensitivity pots went bad? What should I start checking for?

Thanks.
 
for the sensitivity pot (on both pin pointers), I see it says 500 Ohm. On the low side my multimeter shows 1.8ohm, then on the higher side it shows about 400, then ZERO ohm if i turn the nob any higher.
I that what the readings are supposed to be?
 
I don't have any experience with this particular pinpointer, however, I would have to agree about the pots. I do know that sometimes problems like this can be solved by carefully cleaning the circuit board with alcohol and a q-tip (battery removed). it has something to do with the flux residue not being completely removed during manufacturing, and over time can cause medium to high resistance shorts, hence, mucking things up a bit. Also, electrolytic capacitors have a tendancy to go bad after long term storage. They can be checked with an analog multimeter with one leg of the cap disconnected from the circuit. JMHO Good luck.
 
for the sensitivity pot (on both pin pointers), I see it says 500 Ohm. On the low side my multimeter shows 1.8ohm, then on the higher side it shows about 400, then ZERO ohm if i turn the nob any higher.
I that what the readings are supposed to be?

Yeah that's messed up. There may be other components on the board affecting the reading but ... I'd expect the pot to go smoothly from zero to 500 ideally. 1.8 is close enough to zero, 400 is not great, but might be close enough to 500. Going to zero past 400 is a problem. Needs cleaning, or replacing I'd say. If you have an analog meter, you can see if the ohms steadily move up from 1.8 to 400 or if the needle dances the whole way, also indicating dirty inside pot.

If I recall correctly, the tiny pot inside works with the main pot to determine how far you turn the main pot to get it on the verge of sounding off. And as I recall further, the detector is temperature sensitive, so if you adjust the tiny pot too much -- on colder days or warmer days the detector may always sound off, or never sound off, regardless of where the main pot is turned.

I remember finding lots of info by googling, sorry I don't know exactly where. Might even be this forum somewhere.
 
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