Surfmaster's coil waveform problem

[kt315]

Ok sir here is the images
[ATTACH]53255[/ATTACH]
[ATTACH]53256[/ATTACH]

looking on the board... i do not think George is able to fix it quickly (

[Qiaozhi]

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!!!.

You haven't given us enough details.
What about the coil?
Is it a commercial one or homemade?
Diameter and number of turns?

As Carl says, it's acting like the coil is not connected.

[Andi68]

The solder joints look bad, there could be cold solder joints

[Lazrdo]

You haven't given us enough details.
What about the coil?
Is it a commercial one or homemade?
Diameter and number of turns?

As Carl says, it's acting like the coil is not connected.

The coil is handmade as it is specified on the original schematic a 23cm diameter coil, 20 turns made with 0.5mm (24 gauge) standard copper enamel coated wire.
and i will check joints again may be the coil's socket isn't connected

[6666]

This is what my surf preamp looks like when both coil and correct damping resistor are both connected. (I am useing what is labelled LF357, dont know if its real)


Then if I remove just the damping resistor you get crazy oscillations.



Then if I remove the coil and just have damping resistor


If I remove both there is just a flat line trace.

[6666]

Are my attachments visible ? some times the forum does silly things with attachments ?

[surfdetector]

Are my attachments visible ? some times the forum does silly things with attachments ?

I can see your attachments just fine. Always good to see the examples of what things should look like as opposed to simply a written explanation, it adds another dimension.

[6666]

I can see your attachments just fine. Always good to see the examples of what things should look like as opposed to simply a written explanation, it adds another dimension.

Thanks sometimes the attachments do strange things

[Vadim18]

This is what my surf preamp looks like when both coil and correct damping resistor are both connected. (I am useing what is labelled LF357, dont know if its real)
[ATTACH]53267[/ATTACH]

Then if I remove just the damping resistor you get crazy oscillations.

[ATTACH]53268[/ATTACH]

Then if I remove the coil and just have damping resistor
[ATTACH]53269[/ATTACH]

If I remove both there is just a flat line trace.

Probably LF357 are relabeled TL071, to long recovery time.
Here is mine, with OP37

[Lazrdo]

This is what my surf preamp looks like when both coil and correct damping resistor are both connected. (I am useing what is labelled LF357, dont know if its real)
[ATTACH]53267[/ATTACH]

Then if I remove just the damping resistor you get crazy oscillations.

[ATTACH]53268[/ATTACH]

Then if I remove the coil and just have damping resistor
[ATTACH]53269[/ATTACH]

If I remove both there is just a flat line trace.

Sorry what do you mean by "my surf preamp"...?!! Which pin do u track?

[6666]

Sorry what do you mean by "my surf preamp"...?!! Which pin do u track?

pin 6, preamp out, where are you taking your wave forms ? and dont forget you should be useing a Pfet so negative battery is ground

[Lazrdo]

pin 6, preamp out, where are you taking your wave forms ? and dont forget you should be useing a Pfet so negative battery is ground

I am using TIP32C and negative supply is my ground. But the signal i showed at the start isn't the pin 6 of the NE5534 . It is the Collector side of the Power Transistor

[Lazrdo]

pin 6, preamp out, where are you taking your wave forms ? and dont forget you should be useing a Pfet so negative battery is ground

OK Sir, Here is the pin 6 trace for my preamp when coil and dump resistor is connected...and sorry for the first image (Consider me a dump resistor)

[kt315]

to my cheap oscilloscope
---
what name is of your oscilloscope?

[Lazrdo]

to my cheap oscilloscope
---
what name is of your oscilloscope?

DSO138