Simple Russian PI detector Pirat

[BKY1337]

I had the black probe at negative rail(battery minus) and the red probe at the pins, voltages are like in the picture.
I dont have the third diode like in your pictures, but i think you mean the two in the middle.

I need to test the voltage after the diodes tomorrow. Maybe thats the problem.

[homefire]

Third diode is just to stop someone from hooking up the battery wrong. The Two Back to Back are the Limiting Diodes.

[BKY1337]

[homefire]

The Voltage Readings taken with Neg Reference are meaningless on the Op Amp inputs. You need to Reference them to Pos.

[BKY1337]

Ok, i have this voltages with pos reference:

Pin1: 1,27V
Pin2: 1,85V
Pin 3: Not measureable because it changes and sometimes the speaker makes a short crack
Pin 4: 8,0V
Pin5: im not sure i think i have forgotten this pin , the next two pins are 6 and 7 or 5 and 7 , im not sure , but i think they are 6/7.
Pin 6: 0,66V
Pin 7: 1,84V
Pin 8: 96,5mV
Pin9: 0,65V
Pin10: rise till 300mV
Pin11:
Pin12:rise till 300mV
Pin13: 0,45V
Pin 14: 36,9mV

I had 300mV after the diodes before , but only for one time. After that it was always 7,8V.

The rail which supplies the K157ud2 from the left side had 7,8V too.

[homefire]

Ok, now your getting places. From your Reading the Op Amp looks to be OK. You need to check Out puts to see if they vary with target or not.

[BKY1337]

I dont know very much about electronics. Can you tell me what do i need to get a sound from a speaker? Which signal is it? How much volts, oscillating or not?

I still have about 7,8V after the diodes.

[homefire]

Use the Trouble Shooting Aid I built for you. You need to follow the Signal through the circuit. the Audio is generated by and comprised of the Signal Generated by the Coil during Switch switch Off time. That in turn is forwarded to the Op Amps. In this simple PI, Only a signal of sufficient power is allowed to Pass on to the Audio Section.

Without a Scope this is no easy task. Use your VOM starting after the First Op Amp and look for Changes of No Target and Target Signals. You should see some differences in signal strength. Next Move to Pin 9? Out put of second Op Amp. Center your Pot. Note your Voltage NO TARGET. Use the Pot or Pots to adjust as so you get the most change in signal from NO Target to Target signal. When this signal is at it's most Positive the T-3 should turn on and you hear the signal.

Waiting.

[BKY1337]

Thanks for your work, i cant do it now , i will do it tomorrow.
I dont have Internet in my workshop and there is my pirat.
I use a 250k pot by the way, not 100k +10k.

I could simply replace all parts except the two ics and hope that it works.
I dont have an oscilloscope.

[homefire]

Do not think the IC is the Issue. Just Setting or the like.

[bernte_one]

hello bky, pls tell us your coil specs
which wire, how much µH?

[BKY1337]

Okay, i made the measurements:

Pin3 AC : 0,047V not varying with target.
Pin 5 AC: 0,150V not varying with target

Outputs of the op amps:

Pin9AC: 0,012V
Pin11AC: 0,007V

both outputs not varying with target. How much should they vary?

How much voltage should i get after the two diodes and before the capacitor. I have almost nothing here measured with positive reference. And i had something about 1,5 V with negative reference. I can remember that my multimeter showed something about 7,8V yesterday. I also have now a frequency at the left bar where the damping resistor is at about 0,45kHz. How can this be?

Diodes?

Coil Specs:

I use the coil from my easytreasure bfo: about 15cm diameter and 12-15 Turns with 0,3mm or 0,25mm enamelled wire. The whole setup worked before like it its, so i dont think that the coil is the problem.

The coil was attached this time while i made the measurements.

[homefire]

Something is wrong for sure. You need to confirm your Fet is Firing. If you place a speaker in side the coil loop you should hear it Humming if it's working. If nothing we figure out what is wrong.

[BKY1337]

I desoldered and tested the diodes , one diode was broken, conductive in both directions. I replaced it.
Then everything was the same. Then i used a new 9V battery and i could hear the speaker sound , but not from the speaker, the sound
came from the coil. Strange thing. I dont know whats wrong.
It sounds like a lot of power is flowing through the coil, or maybe a spark is jumping over a broken wire, it sounds exactly like the pirat sound from the speaker,
but not as loud as from the speaker. The sound doesnt change with a target.

But the speaker should make a sound without coil too.

Do you mean a speaker between one speaker cable and coil input? Or between both coil connectors?

I think i have to measure everything again, but i dont have a new battery now.

But i can remember that i had exactly 0,000mv at two pins at the right side (pin8-14), i think it was the output , or the two unused pins.

Wrong power connection can damge a lot.

[bernte_one]

pls tell your coil specs