help needed with old detector

[dbanner]

O.K I need better pics of wiring in this area only.

[kt315]

load pls pic of bottom board side but not in perspective you did, in direct projection. i wll do lay pic.

[dbanner]

We need pics of wires coming from coil cable attached to mainboard connector strip and better pics of all internal wiring. The idea is for us to be able to see specific wires and where they are connected so we can work out generally how this detector is put together. Then we will know where to look for the fault. If you know how to use a VOM to check for continuity then its easy to check each transistor and diode. There are five PNP transistors 2N3638A(the four black top ones on mainboard and one on smaller board), one 2N4403 PNP( the small one on mainboard) and another transistor on smaller board which i cant see the number on it, plus a few diodes. All these components are easy to check for integrity with a multimeter(VOM). Even you can do it without much any knowledge of electronics.
I think this metal detector is quite rare and worth fixing, but this is just my opinion.

[keith777]

now you are all talking double dutch to me now i have dyslexia quit bad. so that doesn't help much either. i will take some more pics later. not quit sure what to take as i have already taken quite a few now.

[dbanner]

2N4403 connected to coil, not audio. Audio somehow is on smaller board maybe, since i see green wire connected from smaller board to headphone jack. We need some more pics of wiring between boards and controls etc. otherwise can't make heads or tales. This metal detector may have quite unusual design. Could be nice to reverse engineer to see what's really going on. Please provide more pics of internal wiring.

[homefire]

Yep PNP . Most new detectors use something like the MPSA-13 or the like.

[kt315]

golden pins... when it was... pnp type, high HFE, 200mHz.

[homefire]

He only has a limited electronics back ground. This one is going to be challenging.

I think that 2N4403 is your Audio Driver. Photo's of it and all it's connected to would be good. We may be able to determine if it is or is not infact producing a tone even with the speaker / headphone wires botched.

You said you have a VOM ?

[dbanner]

From the picture of the coil indicates a T/R(Transmit/Recieve) detector and not a BFO(beat frequency oscillator) type detector. One can clearly see the recieve coil(small circle at centre). This type coil is known as omega coil design. I see five wires plus a ground wire going to the coil, I suspect there might be additional circuitry in the coil housing but i could be wrong. Assuming you have the correct power supply connected, you should check all transistors and diodes on the main board and the small board. Post some more pics of the wiring between the various boards and controls etc. so i can see more clearly whats going on. If there is no additional circuitry in the coil housing then this will be a straightforward fix.

[keith777]

yes i had both connected up.

[homefire]

Did you use both batteries ? The Odd Ball 4.5 and the 1.5 ? Can you tell me the numbers on this transistor ? I think it's the audio output transistor. I seen a ZENER Diode on the small board that could be a voltage regulator set up.

[keith777]

hi again homefire.
i did try that but i did dot get any sound either. there must be something else going on. i have been testing it using 4.5v as another member suggested it was a px19 battery that it used because of the battery terminal sizes. so i was using a AAA flashlight battery holder for the power source. see pics.

[homefire]

You give in too easy. It would just take you some time. I think if you move ether the Gray or the Yellow wire to the other side of the Jack the speaker would work.

[keith777]

homefire thanks for that.
the yellow wire had came off were the orange wire was soldered on. the orange wire to me some how looked different to the yellow wire. so what i done was i un-soldered the orange wire and strait away i could see that it was a solid wire. so i rubbed the soldering iron around on the headphone pin and bingo. there was loads of small loose wires floating about.

here is a photo of the inside of the machine now. it looks the part but that's all. i did hear a couple of crackle sounds coming from the speaker at the point when i was pushing the main board back in to it's slot.

i am at the stage now of giving up on it. i wish i new more about electronics but sadly i don't. i would of loved to of seen this wounded soldier up and fighting again.

i never thought of showing a pic of the coil. here it is just in-case any of you guys are interested.

[homefire]

There seems to be a bit of wire protruding from the pin with the Orange wire on opposite side. The Head phone jack opens the contacts to the speaker when a plug is jacked in and deverts the signal to the Head phones. You need to see what pins are doing that. I think if you use a Ohm meter between the Gray wire and the Orange wire you will find that's the case when a plug is jacked in.