Difference in Tesoro coils

[Koala]

What is the difference between the two types of coil Tesoro make

Delta Coils ((4-pin HOT(High Output Technology))
Epsilon Coils (5-pin µmax coils)


Name TX-L TX-R (ohms) TX-fo TX wire RX-L RX-R (ohms) RX-fo RX wire
Brown 8" 5.59mH 21.2 --- --- 6.23mH 22.1 --- ---
White 8" 5.68mH 21.8 --- --- 6.36mH 22.8 --- ---
White 4" 5.62mH 26.6 --- --- 6.13mH 28.2 --- ---
uMax 9x8 5.74mH 24.6 --- --- 6.21mH 25.8 --- ---
uMax 12x10 5.78mH 17.3 --- --- 6.15mH 18.9 --- ---


Specifications look very similar between the two



Trying to build a concentric 5.75" for a Bandido II µmax but can't find any specifications. The only information I have found is

5,75 "concentric
............................. Rx (2-4) 65,0 Ohm .......... 68.38 kHz
............................. Tx (1-3) 3,8 Ohm ............ 251 0 kHz .......... 5 mV

resistance looks to high?? on the Rx and very low on the Tx more like a Lobo

[Qiaozhi]

The Bandido use the 5-pin version.

In the past I've measured the 5-pin coil as: TX = 5.9mH and RX = 6.5mH. I don't recall the resistance values, but these aren't really important.

And, just now, I've measured a 4-pin coil as: TX =981.6uH (4.4 ohms) and RX = 15.52mH (65.6 ohms). So, approximately 1mH (TX) and 15mH (RX).

[Koala]

Many thanks for going to the trouble of measuring the coil

More confused than ever.


There are 4 versions of the Bandido

Bandido
Bandido II
Bandido µmax
and Bandido II µmax





According to http://www.tesoro.com/product/coils/ there are only two groups of coils. "Epsilon coils have 5-pin connectors and are designed for µmax coils"

So guess two of the Bandidos will use the 4 pin and the others the 5 pin

And will mean "5-pin coil as: TX = 5.9mH and RX = 6.5mH" would be correct for my µmax



Same specifications as the coils on the TGS thread which is not µmax detector.


Guess some of the old detectors did not follow the modern name identification

[Qiaozhi]

The Tesoro website information is a bit arbitrary. They list the Cibola, Vaquero, Tejon and Lobo as using Delta (4-pin) coils, and Cortes, Silver uMax and Outlaw as using Epsilon (5-pin) coils. But the detector index of latest models also includes the Compadre (which I guess is an Epsilon type) although it's not specified.

Unless anyone knows better, AFAIK all the Bandidos use the Epsilon (5-pin) coil.

[Koala]

wound the Tx today epoxy now drying

diameter 150mm
wire .28mm
140 turns

scoped the Tx and took a few turns off until it was outputting 9.9 KHz resistance was 17 ohms and 10.1V peak to peak so looks to be in the right ball park.

little kink not a pure sign wave don't think it will affect anything.

Been reading Don Bowers article/PDF on concentric coils for the TGSL


He checks the inductance of the Rx by connecting it to the Tx and measuring the frequency. Need a little help here as the maths is beyond me

I shall be aiming for around 6.2mH

[Qiaozhi]

little kink not a pure sign wave don't think it will affect anything.

The kink in the waveform is normal for Tesoro.

Been reading Don Bowers article/PDF on concentric coils for the TGSL

He checks the inductance of the Rx by connecting it to the Tx and measuring the frequency. Need a little help here as the maths is beyond me

I shall be aiming for around 6.2mH

Assuming the parallel capacitor is 33nF, then the frequency you want (with the RX coil connected to the transmitter circuit) is approximately 11kHz.
The equation is:

[Koala]

Got a bit further with the coil.

Different size capacitor in the TX. Anyhow found someone had measured the Rx connected to the Tx at 10.5Khz so used his figures as a starting point.


Used some 1.5mm wire I had to make the packaging easier worked out at 230 turns on 64 mm diameter with just under 40 for the buck

Must be close as ferrite is rejected at the centre position of the ground potentiometer.

Can't seem to be able to null below 8mv (will give it another go tomorrow) and performance on a Victorian penny is terrible but average on very small silver.


Not sure if it's my coil or detector at fault or just the fact I am testing in the house. Disc mode is always bad but in all metal mode/manual mode sometime you get an extra inch or more after pressing the retune button and sometimes it becomes unstable but works to a reasonable depth.

[Qiaozhi]

Can't seem to be able to null below 8mv (will give it another go tomorrow) and performance on a Victorian penny is terrible but average on very small silver.

This is a common fallacy amongst DIY coil builders. It is not necessary to get the null as close as possible to 0V. If you measure the null on a commercial Tesoro coil, it's usually between 10mV and 20mV. This is because it's more important to get the phase-shift correct between TX and RX than to reduce the null voltage.

[Koala]

Thanks I wont beat myself up about the null.


Have to make an enclosure for it and get the PCB shielded.


After a few retunes I can get All Metal mode to give good depth so guess coil is okay


Just needs gluing up.


Have to admit this coil is so stable compared to a DD on my IDX. Even without a shield connected yet.


Going to call this done and dusted. Shortage of disc depth I need looks to be elsewhere if still the same after testing outside.