Metal Detector 1020A

[barry wilkins]

Does anybody know how one of these works ,its a Maplin one which appears to be a Gold Digger . It finds metal objects which show on the lcd ,but there is no sound ?,which means a lot of it is working.
The speaker is driven by a pair of transistor that look like a Darlington configuration which appears to be OK .The fault must lye further back somewhere.

Barry Wilkins

[stj]

Re: Metal Detector 1020A

foto's

[ant3202]

Re: Metal Detector 1020A

what kind of speaker???... i believe could be a piezo buzzer

some pics are a good way to start..

[barry wilkins]

Re: Metal Detector 1020A

Its a little speaker ,I have attached a picture of the pcb.
Not sure yet but the audio might come out of the MCU chip pin 15. It would help if I could get a circuit ,but it does not seem possible.

Barry Wilkins

[budm]

Re: Metal Detector 1020A

Which connector is used to connect to the speaker/headphone?
Pictures of the back side of the board and how this board is connected to other parts of the unit?

[stj]

Re: Metal Detector 1020A

before you do anything else, check the speaker.
i had a bit of outdoor test kit a few years ago, owner had changed all kinds of parts on the pcb.
problem was simply the wire on the back of the speaker had corroded!

[barry wilkins]

Re: Metal Detector 1020A

The speaker and earphone socket are connected to JK1. I did a quick check when you pass the search coil over a piece of metal pulses come out of the MCU chip pin 15,this is connected to an LM339 pin 10 ,the pulses go in but nothing comes out of pin 13 .Perhaps the next step would be to remove this and do a bit more testing.

Barry Wilkins