GoldScan-6

[Detectorist#1]

Increasing the frequency is a good idea for increasing of the ratio signal/noise, but serious increasing will be done by changing ADA4610 with really low noise operational amplifier type OPA1612AID in first RX stages!

[hunter63]

I am thinking about changing the clock generator from 555 to 4060 or 4046 (PLL) and increasing the frequency from 800 Hz to 1.2 kHz

[hunter63]

Yes it's true

[Detectorist#1]

Also have possibility to disable the work of DC/DC converter during real RX sample time- from start of TX pulse to the end of RX EFE pulse with an additional start-stop trigger in the circuit of the metal detector.

[Detectorist#1]

The 78S40 is in fact MC34063A with added Operational amplifier and 1A diode. Added interference is absolutely the same!

[hunter63]

I disagree, I have been dealing with the 78s40 PWM stabilizer for years and I am satisfied, the price is about 1E, the resistor value is wrong, I usually use 2.2R, while MC34063 introduces interference, best regards

[Detectorist#1]

Hi hunter63,
Also the connecting of 78S40 IC have many, many errors. In this place, it is more suitable to use MC34063A. This IC have more simple connection and the price is 3-4 times cheaper. Read carefully the datasheet - the value of the current sense resistor have to be 150mR, not 150R in your case.

[hunter63]

Right, the other way around Q7
I'm only going to use headphones, thanks for your attention

[Xtrem]

upgraded audio is not correct.

[Detectorist#1]

In the new audio, Q7 have to be connected in reverse polarity (exchange of the emitter and the collector connections). Which type of the speaker you think to use? - the volume of the sound is controlled via 1K potentiometer.

[hunter63]

Which version of GoldScan did you build, version 5 is based on Whites TDI, I saw this detector at a rally and I disagree that it has a poor range, there are videos with Goldscan 5 on YouTube, the ranges are reasonable

[hunter63]

Hello
I am sending upgraded audio

[hunter63]

The diagram provided is a prototype and the audio has been completely changed. Now I'm busy with field service, I'll post the corrected errors in the evening, thanks for the analysis, best regards

[Detectorist#1]

Hi Xtrem,
You are right - the values of R99-R95 and R100-R96 have to exchanged. Also Q9 and Q10 have to be connected in reverse - emitters and collectors have to be exchanged!

[Xtrem]

without being sure, I think the resistances should be reversed.
R99<>R95 R100<>R96
Nice work ....hunter63