Baracuda PI - can't get output of 5534 to ring when adjusting Rdamp, detector works fine though

[Polymer]

I've gotten my old Baracuda boards out, since I have an oscilloscope now.

What has me really is the following:

I can adjust Rdamp from 200 Ohms to 1200 Ohms (I have a 4W pot for this)
The decay curve output of the 5534 hardly changes on the scope when doing this.

When doing this on a Surf PI the output of the 5534 changes dramatically,
from nice decay curve to ringing, multiple ringing curves etc.

The Baracuda is working good and detects a nickel well no matter how I set Rdamp.
This has me very puzzled What is happening here?

Any ideas? Thanks.

[Qiaozhi]

I've gotten my old Baracuda boards out, since I have an oscilloscope now.

What has me really is the following:

I can adjust Rdamp from 200 Ohms to 1200 Ohms (I have a 4W pot for this)
The decay curve output of the 5534 hardly changes on the scope when doing this.

When doing this on a Surf PI the output of the 5534 changes dramatically,
from nice decay curve to ringing, multiple ringing curves etc.

The Baracuda is working good and detects a nickel well no matter how I set Rdamp.
This has me very puzzled What is happening here?

Any ideas? Thanks.

Maybe you already have a damping resistor fitted on the PCB. In the Geotech Baracuda, the damping resistor is R1 (330R).

[homefire]

DHOOOOOOOE ! I think I did something like that in the past.

[Polymer]

Maybe you already have a damping resistor fitted on the PCB. In the Geotech Baracuda, the damping resistor is R1 (330R).

I wish that was the case ... just double checked top and bottom of the pcb and leads to the coil and put my glasses on and no extra Rdamp ...
Just checked again with extra bright light ... no sneaky Rdamp hiding somewhere ... aaarghhh .... I'm getting a beer now.

Tested my Rdamp adjuster with the multimeter, it still does 220 to 1210 Ohms.

[homefire]

What is the coils uH and Ohms ?

[Polymer]

What is the coils uH and Ohms ?

I can't say how much uH, because I think I might have a weird setup in which I can't calculate with the formulas I've found.

The coil has 0.4 Ohms at DC with two 2.2 Ohm resistors in series to limit power.
I have wound the coil on a hollow ferrite with two counterwound coils at 40 turns each, the same wire I use for normal coils (tinned, stranded).
The ferrite has a ui of 2100. I am trying to build a PI-Pinpointer with the old Baracuda PCB's I started a few years ago.