Surf PI Micro Var. 1.00

[BKY1337]

I think the battery pack smoked, not the pcb. I also have no clue how this is possible. Every single battery has 1,5 Volts, all together have 22 Volts.
I will try to set the current limit to 200mA.

[dbanner]

I think the battery pack smoked, not the pcb. I also have no clue how this is possible. Every single battery has 1,5 Volts, all together have 22 Volts.
I will try to set the current limit to 200mA.

You have magical battery pack or your meter has gone nuts.

[Andi68]

I still do not understand why current should be limited.
The current consumption depends on the pulse width.
And how do 8x1,5V to 22V- is this magic?

Basics !!

[waltr]

You have magical battery pack or your meter has gone nuts.

Yea, Check the battery in your meter. Accuracy goes bad when meter battery gets too low.

And like everyone has said---Test the Basics.
Shorts on PCB? check without chips.
etc, etc as has been posted in many threads here.

[BKY1337]

Andi: I think it is better to limit the current because a faulty circuit can draw much more current and something could be destroyed.
I bought this module for this reason. Its only for testing purposes.

I know now that my Mosfet became hot, i think it was the thing which smoked.
I had no spare time today, i will try everything what you said tomorrow.

It is possible that my DMM measures the voltage wrong. In most cases it measures 12V and in some 22V.

[dbanner]

I think you can approach the issue of current limiting to avoid damage from the other way around. Your module is a CV/CC type module. Do not set any limits on the current, instead, begin with 0V, then gradually and slowly increase the voltage while monitoring the current the circuit draws. If you have a short, the current drawn will start increasing quickly, which can be controlled by the voltage. You'll know right away if you have any short without damaging any component because you will just stop increasing voltage before the current runs away sort of like how a varactor would be used.
For example, if your circuit is expected to draw 50mA at idle with 12 volt. But you are approaching 50mA only after increasing voltage to say around 3-5volts, then that's an indication of a short.
Just something to consider.

[BKY1337]

Thanks. Thats a good idea.

With 6 Volts it begins to pull 0.45A. (with coil)

I desoldered the Mosfet and removed all chips except PIC. Now it doesnt draw much current and the sound + pulse came back.
My negative voltage is still at 1,5 Volts. I think the problem is at T2,T3,T4. I will check them tomorrow.

[dbanner]

I'm not sure because I'm looking at schematic you posted and comparing it to the PCB layout. I looked at D1 and D2, something looks wrong when comparing schematic to pcb. On the PCB, D1 and D2 are shown connected anode of D1 to anode of D2, whereas on the schematic the anode of D1 is connected to the cathode of D2.
In other words, on the PCB is shown both anodes connected together, on schematic not so. Check it out cause this part of circuit is responsible for -5V.
The schematic shows the correct arrangement for diodes D1,D2. The error is on the PCB.

[dbanner]

I think D2 needs to be flipped around on the pcb. It is labeled incorrectly on the silkscreen. That will solve your problem of -5V.
You can thank me by getting the device working.

[BKY1337]

Thanks a lot! I hope this solves the problem.

[dbanner]

Make sure you flip the correct diode. D2 is the diode closest to the 470uF electrolytic capacitor(C5), not the zener diode but the other one right next to C5.

[Andi68]

https://www.youtube.com/watch?v=CO7-YVEhM9g

https://www.vishay.com/docs/85718/bav99.pdf

[BKY1337]

Lol

Thanks. I need to desolder C5 too because it covers the diode.

Do you think this caused that the mosfet became hot?

[dbanner]

Lol

Thanks. I need to desolder C5 too because it covers the diode.

Do you think this caused that the mosfet became hot?

I think it would, because MOSFET would then be switched on all the time.
Make the changes and see you're getting -5v. Don't put the MOSFET back in as yet. Check for all your proper voltages first.

[dbanner]

https://www.youtube.com/watch?v=CO7-YVEhM9g

https://www.vishay.com/docs/85718/bav99.pdf

I looked at the datasheet, well that's not on the PCB. The PCB has two individual diodes for D1,D2 probably 1N4148.