help needed with old detector

[keith777]

Hi again dabanner.

here is the result that i got for that transistor test. i think i had the meter setup right. the 254 number was slow to build up. the other number went strait up. pics bellow.

[dbanner]

Good idea. Either way, get that transistor checked, if it tests good then all your transistors and diodes check out o.k. You will then have to look for bad capacitors or possible a damaged coil.

[6666]

perform one last test. Set up multimeter to check transistors as before only this time remove base leg and place red probe to base leg and black probe to each of the other legs. Test this transistor on small board.

removing the leg from the pcb is one way to do it, but it can cause damage to track and transistor , Its a simple pcb, so another way and much less messy and less work is to just cut the track with a razor blade and resolder,

[dbanner]

perform one last test. Set up multimeter to check transistors as before only this time remove base leg and place red probe to base leg and black probe to each of the other legs. Test this transistor on small board.

[keith777]

Hi again dabanner.

here is some pics bellow. also i tried changing that 30K resistor that i used for a 10k resistor. the color bands on it were (brown, black, orange, gold) it still made no difference.

[dbanner]

Cheers. First of all, the wires from the first coil were black, red, white, and green, brade. What do the wires from the second coil look like-are they the same? Post a pic so i can see.

[keith777]

Hi again dabanner.

there is no small circuit board on this one. also no speaker. just a head phone socket that allows you to use headphones with or with out the meter attached. how would i compare measurements with the coil?

cheers mate.

[dbanner]

AS for the battery terminals, I don't think anyone changed them since the battery holder is definitely not for typical 9V battery but rather some round, circular battery. The 30K on small board still bothers me. I think it should be 10K(brown, black, orange). I see a lot of 10K resistors on other detector circuit board but i haven't seen any 30K resistor used anywhere else on any board on both detectors.

[dbanner]

WOW! That's really nice. It's in fine condition too. My internet connection just started working again. This detector is a bit more advanced than the other one. Check the coil wires and see if they are the same as the other one. If they are, then you can compare measurements to determine if the other coil on the non working detector checks out good. Does this detector have a small circuit board like the other one did?

[keith777]

Hi again dabanner.

i have managed to get a hold of another metal detector made by the same company as the one we are testing. it has the same type coil and the main board is setup in the same way, just some of the components are a bit different. guess what. this one uses a regular 9V battery.
this one works....

i wonder if someone changed the battery terminals on the faulty one for some strange reason?

[keith777]

i for got to say that the speaker defiantly works. i de-soldered the wires and hooked them up to a audio cable to a mp3 player. it played music just fine.

[keith777]

thanks mate.
i really hope you don't mind all this hassle.

[dbanner]

O.K. You have to take some voltage measurements while detector is on. At this point I am suspicious of coil, but I wil be back with a drawing of where i want you to measure.

[keith777]

no sound with either test.
what i can hear is though. if you leave the volume control fully up. then switch on the machine, you hear a click sound come from the speaker.

[dbanner]

Also, while detector is on, adjust treshold control(the 10K), is there any sound?