PI5 from ITMD

[geoscash1]

Hi Ray,

based on your explanation then the correct connection should look like this:



versus how it was:



If that is right then how would I go about jumping or fixing the board I have made (based on the pcb shown above in other post)?

the 1.2k should go right to base of the 3904 but how would I get around the pre fabbed connections for the pot? Thats probably a dumb question but for whatever reason it is not clear in my head..

[raygdunn]

Hi Ray,

based on your explanation then the correct connection should look like this:

[ATTACH]37309[/ATTACH]

versus how it was:

[ATTACH]37310[/ATTACH]

If that is right then how would I go about jumping or fixing the board I have made (based on the pcb shown above in other post)?

the 1.2k should go right to base of the 3904 but how would I get around the pre fabbed connections for the pot? Thats probably a dumb question but for whatever reason it is not clear in my head..

Yes as in your diagrams, in my opinion.

I think you just remove the pot. from the PCB and you have the connections required in your revised diagram.

Ray

[geoscash1]

Yes as in your diagrams, in my opinion.

I think you just remove the pot. from the PCB and you have the connections required in your revised diagram.

Ray

Thanks ray, thats kinda what I thought but wasnt sure based on the split connection from the pot to the 555.

I gave it a whirl and still get nothing though so there must be another issue elsewhere. I changed out the 555, 3904 and the 10R resistor as they were smoked but still not working.
Have power at all points so not sure what or where else to look with this thing.... Dang, was hoping that pot removed and new parts would be the fix...

[raygdunn]

Thanks ray, thats kinda what I thought but wasnt sure based on the split connection from the pot to the 555.

I gave it a whirl and still get nothing though so there must be another issue elsewhere. I changed out the 555, 3904 and the 10R resistor as they were smoked but still not working.
Have power at all points so not sure what or where else to look with this thing.... Dang, was hoping that pot removed and new parts would be the fix...

In theory I still have most of the circuit on a breadboard. If you could give me your exact supply voltage, I'll try and give you some readings on the chip pins. I know they are not static voltages. But some ballpark figures should give clues. Let's hope I have enough to reconstruct a working for circuit again.

Do I take it that you don't have a scope?

Ray

[geoscash1]

Hi Ray,

Yep, I have a scope, just not enough electronics knowledge with this stuff to know where to start probing and what I'm actually looking for. I am using a rechargable 12v supply. I have tried using my bench supply with different settings and also 12.6v on three rechargbles. didnt seem to matter what the voltage was.

That would be cool to see what the chip pins give as far as voltage goes. I usually only check the voltages where the power pin is on each individual chip.

[raygdunn]

Hi Ray,

Yep, I have a scope, just not enough electronics knowledge with this stuff to know where to start probing and what I'm actually looking for. I am using a rechargable 12v supply. I have tried using my bench supply with different settings and also 12.6v on three rechargbles. didnt seem to matter what the voltage was.

That would be cool to see what the chip pins give as far as voltage goes. I usually only check the voltages where the power pin is on each individual chip.

Bah. I've been here before I think. I do apologise. On the breadboard I have a PI-4 with the micro-processor back end. Plan B time...

Digging back though the thread, I found more details you have posted previously. At the time I was struggling with understanding the Barracuda. Can I suggest some tests for the scope based on that... I'm no expert 😞 Health warning applies☺

(Hopefully you are happy that a little over 12V is OK for the circuit, as was originally 9V. I've failed to confirm that so far.)

So one scope lead on the negative earth and with your PCB oriented with the word SPEAKER at the bottom.

(For anyone else reading this, references apply to the custom PCB not the schema. The designer software has allocated it's own numbering)

To check the timing pulse generator: (IC1 bottom left on your PCB). Pin 3 should show a square wave (of less than your supply voltage of 12V) if it is working.

Keeping clear of the coil area for now, if connected, as has that very high reverse voltage, which could kill the scope.

The next test point is the small voltage (less than a volt) across the diode pair D1, D2: test the end of either diode nearest the top of the board. If working there will be the squarish positive pulse followed be the brief negative, with that sloping trailing edge that we are all interested in.

Next point is the output of the preamp (5532 top right of centre): Output pin 1 should show the amplified previous signal.

The original positive pulse is filtered out by diode D3 (near top right edge).

We then go though those logic gates in the 4011 top right:
Pin 3 should show a now single pulse of near the supply voltage.
Pin 4 should show the same signal inverted.
Pins 10 and 11 will only show any pulses, if everything except the audio is functioning (including the second 555 checked below).

Looking at the sampling delay from the second 555 bottom right (IC2 on your PCB):
Pin 2 should have the input pulse starting the timer.
Pin 3 should have the output pulse after the delay time (controlled by pot. R18 on your PCB)

Then you are into the audio section.

I hope that makes sense and forms a useful initial test plan to isolate the problem.

Over to you...

Ray

[geoscash1]

Thanks Ray, I'll run thru those test points today when I return from the doctors, thanks for your excellent advice.

[Qiaozhi]

After a cursory glance over the PCB layout, it is fairly obvious that the 5k pot is incorrectly connected. The layout has it connected between R15/C9 junction and +VB.

If you remove the 2N3904, 10R resistor, 5k pot and speaker; what does the audio signal at the junction of R15 (1k2) and C9 (100nF) look like on the scope? You should see a VCO style signal at this point which varies when a target is close to the coil.

Note that either the headphone circuit or the speaker circuit should be connected to hear the audio output, but not both together.

[bernte_one]

pi5 is still a mystery machine

[surfdetector]

pi5 is still a mystery machine

I am surprised that this topic did not ever take off and become an official project in its own right.

[Qiaozhi]

I am surprised that this topic did not ever take off and become an official project in its own right.

Been busy with other projects, so this one slipped through the cracks. It's on my list to revisit. If/when, I'll post the full details in the forum as a new project.
Don't hold your breath though .....it might take awhile.

[surfdetector]

Been busy with other projects, so this one slipped through the cracks. It's on my list to revisit. If/when, I'll post the full details in the forum as a new project.
Don't hold your breath though .....it might take awhile.

I look forward to it.
Cheers