PCB Problem

[hug-fred]

I ordered this PCB, assembled all the components, but the circuit didn't work at all. After doing some troubleshooting, I found major routing mistakes on the PCB compared to the official schematic:

1. The Emitter and Base pins of transistor Q5 are swapped.
2. The bases of transistors Q3 and Q4 are shorted to the ground (GND) instead of being properly routed to C1 and C2.

Because of these critical design flaws, the board is non-functional. I haven't yet tested if modifying these connections will make it work but I will keep you updated !

[kjellfredrik-dot]

Q3 & Q4 are according to the schematic, but if you read it it says pin 2 to ground & pin 1 to C1/C2
and Q5 pin 1 = R8 pin 2 = R9 and pin 3 V+
??
but surely there is a mistake somewhere?

[hug-fred]

I switch Q5 base and emitter and now the LED is working. Then I also switch Q3 and Q4 base and emitter and I still don't have an output signal. However it seems to oscillate corectly.
As you can see in the 2N3904 datasheet, the pin are not at the same place on the electrical plan and the PCB.

[kjellfredrik-dot]

I've been staring at the PCB in the video for a while now, and it's not the same as the one in the gerber.
Back to basic and run a point to point, so we'll see if the errors can be detected?
Keep the thread updated so we can resolve this.
//Bless

[hug-fred]

For sure, I'm currently on it to solve the problem!

[kjellfredrik-dot]

Same problem on potentiometer , pin 2 & 3 are swapped

[ECTO-1A]

For sure, I'm currently on it to solve the problem!

Were you ever able to get this working? I think I'm in the same situation as you were

[hug-fred]

I have spent a lot of time on this. I tested all the connections on the PCB but couldn't find a solution. My research is currently on hold, but I’m hoping someone else will be able to identify the problem with this circuit!

[DamianRoberts432]

Ok I switched E and B around for my q5, q3,and q4, and when I flicked the mute switch 3PDT, I heard sound for a moment: it wants to make sound if I hold it in between the on/off. I'll try soldering those in different positions now.

[DamianRoberts432]

Here's what I did:

Fix the legs for your q5, q4, q3.
I used on/off/on switch for the mute instead. 3pin obviously.

I also added two power switches but parallel: one of them latching on/off. The other is on/off/on momentary. The second "on" I added a 1000nf capacitor that connects to the other on. That way with Auto selected I can make a short signal, and the cap side takes a moment to fill causing a slow rise.

[ahuault]

Hello everyone,

I also ordered this PCB and assembled all the components in order to offer it to my friend for his birthday in 3 days. After several days of being mad to myself I just see this conversation today.
Is it an easy and fast way to save my PCB and have a chance to make this siren sing before my friend birthday ?
Otherwise I will build it on a veroboard, are we sure that the schematic in PDF is working well ?

thank you

[DamianRoberts432]

Switch the legs on your transistors, use a three way switch on off on for the mute.
Everything works great if you do those two adjustments.

[ahuault]

thanks a lot !

[DamianRoberts432]

thanks a lot !

No worries! I bought a bunch of the recommended parts, but found using regular potentiometers was better for aluminum enclosure housing.

Next one I build I'll try the rotary knob on the other side rather than wiring it off board.