Surfmaster's coil waveform problem

[Lazrdo]

Greetings!

I need help with my self-made 1 layer pcb surfmaster. The waveform according to my cheap oscilloscope (Which i can't screenshot it here) . it would look like the pink line on the attached image no matter what dump resistor is it. (Thank for Tepco's waveform images). And one more thing no sound at all.

[Carl-NC]

If you completely remove the damping resistor do you get the same waveform?

[Lazrdo]

If you completely remove the damping resistor do you get the same waveform?

Actually my dump resistor is 1K trimmer connected in parallel with the coil as variable resistor. No matter I rotate it CW or CCW, the waveform is the same.

[Carl-NC]

Remove the damping R... what do you get?

Remove the coil... what do you get?

[kt315]

Actually my dump resistor is 1K trimmer connected in parallel with the coil as variable resistor. No matter I rotate it CW or CCW, the waveform is the same.

your trimmer is low voltage and lowest power type. you must use high voltage type and with power >=2W, wire type, not resistive layer covered type.

look pics https://www.google.com/search?q=%D0%...h=865&biw=1280

[Lazrdo]

Remove the damping R... what do you get?

Remove the coil... what do you get?

OK Sir, I removed Dump resistor and here is the waveform (RED LINE)


And the same waveform after removing the coil but pure square wave for TX Period and no small notch for RX Period like the red line.

[Lazrdo]

your trimmer is low voltage and lowest power type. you must use high voltage type and with power >=2W, wire type, not resistive layer covered type.

look pics https://www.google.com/search?q=%D0%...h=865&biw=1280

What to do if i can't get such a trimmer

[kt315]

What to do if i can't get such a trimmer

use a diggest of resistors - 820, 750, 680, 620, 560, 470, Ohm. on a bread board.
https://www.google.com/search?q=brea...w=1018&bih=865


or George's/ITMD damping tuning schematic.

[Lazrdo]

Guys, I Know I may be seems to be new here but I have been here for awhile surfing the threads to do it right. I really need help because i need it up and running soon. And i will build it from scratch again.

[6666]

OK Sir, I removed Dump resistor and here is the waveform (RED LINE)
[ATTACH]53250[/ATTACH]

And the same waveform after removing the coil but pure square wave for TX Period and no small notch for RX Period like the red line.

Can you show some pictures of the pcb ?

[Carl-NC]

OK Sir, I removed Dump resistor and here is the waveform (RED LINE)
[ATTACH]53250[/ATTACH]

And the same waveform after removing the coil but pure square wave for TX Period and no small notch for RX Period like the red line.

It looks to me like your coil is not actually getting connected to the circuit. Maybe you have a break in the cable wiring.

[kt315]

OK Sir, I removed Dump resistor and here is the waveform (RED LINE)
[ATTACH]53250[/ATTACH]

And the same waveform after removing the coil but pure square wave for TX Period and no small notch for RX Period like the red line.

check diodes on op amp input. i see one is shorted.

[Lazrdo]

Can you show some pictures of the pcb ?

Ok sir here is the images

[Lazrdo]

It looks to me like your coil is not actually getting connected to the circuit. Maybe you have a break in the cable wiring.

It isn't broken because when i test it with continuity mode using the multi-meter it beeps

[Lazrdo]

check diodes on op amp input. i see one is shorted.

None is shorted.
And when i hold the coil with my hand. The op amp pin 6 goes from 0v (Calibrated with offset pot) to 0.58v. no respond from the coil but that. and still no sound even with that!!!.