How does a manufacturer test a detector?

[bklein]

Tried the DF out in the front yard street, held it parallel to the ground, EMI was minimal.
The DF seems to go from whimper to solid target tone pretty quickly - within an inch or two on any target.
The following are distances from the coil when it turns solid:
Penny 7"
Dime 6"
Nickel 7:
Quarter 7"
Kennedy half dollar 7".
This is with pulse delay switched on but at minimal (by the switch) setting.
If I switch it off the nickel depth gains an inch to 8" but that's it - others stay the same.

[Koala]

Tried the DF out in the front yard street, held it parallel to the ground, EMI was minimal.
The DF seems to go from whimper to solid target tone pretty quickly - within an inch or two on any target.
The following are distances from the coil when it turns solid:
Penny 7"
Dime 6"
Nickel 7:
Quarter 7"
Kennedy half dollar 7".
This is with pulse delay switched on but at minimal (by the switch) setting.
If I switch it off the nickel depth gains an inch to 8" but that's it - others stay the same.

on the test I posted there is a dim bottom right

is the Kennedy a modern clad or original silver "

gain fully clockwise
pulse timing fully anti clockwise
threshold faint hum

should give maximum depth.

[bklein]

1968-D, probably clad but I don’t see the copper layer.

[Koala]

60% silver 40% copper nearly 31 mm 11.5 gams

7" on such a large coin doesn't sound right to me I am nearly double that on my Baracuda. Think we need someone with a dual field to chime in with some comparisons.

being at the other end of the scale to gold it doesn't look like the problem is the delay

it appears you are down on depth on all target types.

[Koala]

https://www.youtube.com/watch?v=RfAOJTAAV4w

[bklein]

Icl7660 V- is -4.75V.
Seems should be -5.0, yes? V+ good.

[bklein]

One sample PW 39uS, other 43. Starts 195uS apart.

[Koala]

measured with your scope what is the voltage on pin 6 of the 5534 ?

[Koala]

Icl7660 V- is -4.75V.
Seems should be -5.0, yes? V+ good.

-4.75V is good

[dbanner]

That dual field coil might be bad, or improperly damped. Dig up the timings regime and compare it to what you've got. I can't remember. If all is well with the circuit, then it's probably the coil.

[dbanner]

Yours should resemble this.

[bklein]

measured with your scope what is the voltage on pin 6 of the 5534 ?

trimpot was set correctly for zero baseline offset

[dbanner]

I think you have bad coil, inner coil alone is working, outer coil maybe not. Put object on edge of outer coil and check for response.

[bklein]

This guy seems to have one as bad as mine and thinks it’s ok: https://m.youtube.com/watch?v=sWKM39s82nY#dialog

This guy’s seems to work better: https://youtu.be/RfAOJTAAV4w

[Koala]

I think you have bad coil, inner coil alone is working, outer coil maybe not. Put object on edge of outer coil and check for response.

Good idea.

I believe they are wired in series so if one fails they both fail.