Baracuda broken

[6666]

I completely pulled out two through hole platings where the mosfet is.
Was not a good Idea to desolder the mosfet.

Here is the Signal from the gate of the Mosfet, with desoldered Mosfet.

[ATTACH]42475[/ATTACH]

I can not measure anything at pin8.

Sounds like your PCB needs some repairs, you should always mount mosfets, voltage regs etc on pcb pins , makes it very easy to remove or replace when required.

[kt315]

temporarely use TIP127, for only seeking the problem.

[BKY1337]

I need to buy parts first. Is the picture ok?

[6666]

My picture is from the MPP pi project, but it shows about mounting mosfets on PCB pins

[BKY1337]

I dont mean your picture. Thanks for it by the way, i will make it like this in the future.

I have meant the oscilloscope picture. I dont think that i can measure a signal at pin 8 U4 without connected coil or can i?

Now i try to measure all the pulses from the geotech Rev-A pdf.

[kt315]

guys

ask what o-scope pic you need.

[BKY1337]

I have meant the osc. picture from my gate. Is it normal?

I have a problem with my dso , i can not adjust the level at the right side anymore.
But i saw that i have something similar like the picture in your video with coil and 9 Volts.
This Wave changes a lot when i connect 12V and a coil. I have repaired the mosfet holes and soldered it in.
I get Spikes , it was TP 2 i guess (left from U4).

It still works with 9V , not with 12V. Tx Wave looks like in the baracuda PDF.

[BKY1337]

I can not adjust pin 6 to 0 Volts. It is at 4 Volts and i can only adjust it to about 3.6 Volts with a 12V Battery.
I can adjust it to 0 Volts with a 9 Volt Battery and i have 27-30 cm depht at a 1 euro coin with a full charged battery.

I dont know why the mosfet gets hot.
It maybe works when i connect the 12V to the Mosfet and use a 9V for the circuit, but i dont think that this is a good solution.

[Koala]

I take it the FET is getting very hot. It should only be getting warm and can be run without a heat shield for testing. I would guess the problem is due to something around the 2n2222. Is it the right way round. There are several versions and some have to be inserted 180 degrees to the legend.

[BKY1337]

It was the problem. I tested it before i soldered it in and my transistor tester showed ok. But i can see that it shows the same when i turn it 180 degree.
Unfortunately the depht didnt increase. I used a 2N3904 instead of a 2N2222. I have 30cm. With background noise i can get about 35cm. I need to play a bit with the trimmers and pots.

Thanks a lot!

[6666]

So the 2222 was in backwards , thats a pity, the 2222 comes in many pin configurations , a long time ago I made the suggestion for George and Silverdog to change the 2222 to another transistor that only has one pin silkscreen footprint so nobody would make this mistake again.

[kt315]

if i do something i always check. i have mine done a haracteriograf, like a console for o-scope.
i see clearly where collector base and emitter, also a type npn or pnp, on o-scope screen. NO MISTAKES.
so if i wrote PN2222 its i did KEEP IT in my hands.

[Koala]

So the 2222 was in backwards , thats a pity, the 2222 comes in many pin configurations , a long time ago I made the suggestion for George and Silverdog to change the 2222 to another transistor that only has one pin silkscreen footprint so nobody would make this mistake again.

I have had two problems with the 2N2222A the first was I checked the pin out on the internet and at least one site has it wrong. The second was the Barracuda I ordered 2N2222A but received PN2N2222A from an eBay supplier never checked just fitted then wasted hours trying to get it working.

Funnily enough once the battery volts lowered it ran very well.

Ah well. Live and lean.

[Koala]

It was the problem. I tested it before i soldered it in and my transistor tester showed ok. But i can see that it shows the same when i turn it 180 degree.
Unfortunately the depht didnt increase. I used a 2N3904 instead of a 2N2222. I have 30cm. With background noise i can get about 35cm. I need to play a bit with the trimmers and pots.

Thanks a lot!

35cm is about right for most coin size targets and a 8" coil.
Make sure you test with copper, gold, silver, lead and so on. Best depth on a ladies gold ring will half the depth on a small Roman copper coin. Delay is a compromise. Set it with targets you hope to find.

[kt315]

guys

use chinese tester. https://www.ebay.com/itm/2017-DIY-KI...MAAOSwHtFZu3z2

ATTENTION. pins' SMD placement on the board ARE WRONG, on right side from the socket.
you have to know it. i mean the chinese tester.