Surf 1.2 PI power supply advice requested please

[Magnette]

Hi Waikiki,

I took the precaution of re-soldering every joint on the board incase of a dry joint. Sadly though, this appears to have made things worse. When I now try to tune the offset pot to 0v, it is constantly creeping upwards and I cannot seem to stabilise it. Any advice would be appreciated. I would like to get this board working, but my electronics knowledge is limited I'm afraid.

Thanks, Magnette

[Tepco]

First clean the board with some solvent, alcohol, acetone... and try again.

[Waikiki_Sweep]

Check if you have +5V and -5V now after your last re-soldering. Check your soldering around NE5534 area did you shorted something. Try to replace 100k pot you using to set offset. If you have no replacement you can use "delay" pot that has same 100k if you will be able to de-solder it. Delay and offset pots broke for overheat or overuse sometimes.

[Magnette]

Cheers guys,

I will pop by my local Maplins when I get a chance and buy some new bits, then give it a go.

[golfnut]

This is for later on, when your off first base.. I made 2 coils for surf .. the first one was smaller 7" the second a larger one 10". The best results for me was with the smaller coil on smaller targets like coins. S

[Waikiki_Sweep]

This is for later on, when your off first base.. I made 2 coils for surf .. the first one was smaller 7" the second a larger one 10". The best results for me was with the smaller coil on smaller targets like coins. S

Looks like it is choice of taste I considering my best coil 17" long and 9" wide. It helps me to cover that square miles of ocean sandbanks to find lost jewelry much faster then with regular coil.

18 turns of 24 AWG, PTFE insulated, 19 strands stranded, silver plated wire making 300uH inductance if someone wants to make such coil. You will need approximately 65 ft. of that amazing Teflon insulated wire from eBay.

[medj]

The easiest device to detect metals
I've created which works well
XXXXX
http://www.easytreasure.co.uk/bfo.htm

[Waikiki_Sweep]

Great job! Probably you can design some very simple Pulse Induction detector too because even simple PI can go twice deeper (25 cm instead 12 cm for coin with BFO) and also withstand harsh conditions like salt water and mineralization. There are many ready to use modules on the forum (MOSFET drivers, preamplifiers, integrators, e.t.c.) to combine into something little and cute but hell powerful.

[6666]

Hi Waikiki,
because its so big, Does your best coil 17" long and 9" wide, reduce responses to crappy targets like foil etc ?
thanks

[Waikiki_Sweep]

Hi Waikiki,
because its so big, Does your best coil 17" long and 9" wide, reduce responses to crappy targets like foil etc ?
thanks

Not so big as it sounds because it is long so total area is big but not too much bigger than 12" Dualfield coil.
Regarding junk. It depends on delay setting. But because I am hunting on gold jewelry that decays very fast I am trying to have as smaller delay as I can and yes I am digging all foil too.
Also I am digging errings with only 8 mm long and less than 1 mm in diameter metal part. So I can't tell that I lost sensitivity to small targets.
At least I can not hear that 3 mm cooper BB's some of crazy competitors with Dualfield detectors dumping on the beach to make other detectorists with Minlab Excaliburs frustrated.

[6666]

I am digging all foil too.

Interesting thanks.

[Waikiki_Sweep]

I have tested with Garrett ACE 250 that I can detect 3x3 mm piece of aluminum foil.
With my PI detector I need a piece of foil that several times bigger to detect.
Probably it is an improvement to escape from digging at least small pieces of foil.

[golfnut]

with my surf I can detect foil approx 4x4cm but when that foil is lightly crushed to thumbnail size it does not detect. 10" coil.

Small coins detect fine.

[Waikiki_Sweep]

Yep. I just checked it with kitchen foil and get same 4x4cm. for my 17"x9" coil. Looks like we have same delay. Also I have added HER208 diode in series with MOSFET recently and saw depth increasing for such objects as foil because coil discharging faster when high capacitance of MOSFET is isolated from the coil by low capacitance fast diode.

Also I see that my another detector with smaller 15" x 7.5" coil detecting same 4x4cm foil from twice longer distance. But I know that detector horribly underdamped as I saw on oscilloscope. But number of gold items found with it was outstanding.
Underdumping is a dark territory that may hold some magic secrets.