TESORO GOLDEN SABRE

[sdesic]

Today I had few seconds of smoke from detector - connected body of two pots and body of disc switch ...
Box is not metal so I wanted to ground them.
Lucky me ... it was not burned and other components did not burn too.

[golfnut]

"Even having boards made, money can be possibly saved by not having the vias, though for one offs, the savings would be probably quite small. I have never had professional boards, "made", only simply bought "their" finished product!! Just a thought though!!"

Years ago the technicians at Marconi used small rivet like parts to repair damaged vias.

They were tubular with a washer like end. You drilled out the via and removed the resist top and bottom. Insert the via rivet and solder the washer end.

Filp, and open out the tube with a center punch and solder it.


A bit of bare tinned copper would be similar, but they were simple and effective and reliable enough to pass CAA air worthiness regs.

[der_fisherman]

Such parts were once (still?) available from a big electronic company in the UK, RS Components.....
If they do not have them (no idea!) maybe Maplin can help.
For other countries I have no idea, sorry.
I always used bits or wire when I could not use a component to make the connection....never had problems...
Regards
Andy

[sdesic]

Today I went on hunt with my TGSL and got some silver (from 1594) but I have broken disc switch ...
and then it fell back on rest of PCB connecting something...
(I detect in all metal mode and switch to disc to find if it is iron or not every time)

Now I have replaced switch but I have only disc part working OK ... 30-35 cm coin and all
rejection of iron, foil and that it OK.

On all metal I have only brokend sound and less sensitivity ... only detects large metal and very close to coil.
Don't have many parts on hand now and need some idea of what to look for or change.

[Silver Dollar]

Most likely you blew one of the FETs but it's funny Disc still works.
I'd check the power (+ and -), the TX and then the two chains
while waving a target to see if one opamp output got popped.

[sdesic]

I had similar problem with my old tgsl.
FETS were turned 180 deg (american version fets) but it worked with 15 cm max detection.
Tried changing pots as one was burning few days ago - it is not that.
Tried changing cables for pots and disc switch... also nothing.

Will try chasing TX now. probably opamp but ... it is "working" with larger targets

[paku]

[sdesic]

As I wait for parts I was experimenting with coil shielding.
I added 2 layers of electric tape to coils - one (rubbery) loosely and one (normal) tighter and then medical (paper) tape.
On that I applied shielding paste.
Got some graphite (dust) (50g) and used it with "paint" (boat varnish) and applied it to coils.
It is thick layer and it is about 2k from end to end of D shape...
between measurement points is 2 cm gap.
Copper connecting wire was installed before and it is connected good for shield.

Is it too low resistance for shielding ?

[Silver Dollar]

I have read that 10K to 1K per inch is a good range. Lower will reduce your signal a bit...

[sdesic]

I have 2k on whole D shape ... so it is too low ?

[sdesic]

That 2k is my lowest result...
but I have measured 15k on 1 cm and measured 4k on 2 cm

so I need to sand it down a bit ... on few places

[Silver Dollar]

I measured 10k on the bottom of a Tesoro Coil and 5K on the top.
There are huge variations I think and they are not too important.
I wonder why Minelab uses very low values like 100 ohms per inch?

[sdesic]

Thank you Silver Dollar, I will try it in field (wet grass and bumpy ground).
Just need to fit coils into shell - they are oversize for shell no.1 from Georgi.

Null is a bit problematic with big coils.
Also bending them on parts where they are crossing over each other.

[bernte_one]

@sdesic
if you have problem while nulling big coils make it so:
place the two coil so together that you have best null volltage (under 4mV is sometimes to low)
if you ahve best result you can achieve glue you coil all 2cm with hot glue
and set spacer between the gap
the fill coil shell half with epoxi and let it harden
next day measure the null voltage again
if it has drifted take a very small pieces of foil and place it one one side of the coil and set the null voltage again with this smal pieces of foil
if you found the best place glue it in and fill the rest of the epoxi


@paku
have you finished ?

[sdesic]

I have bought White's 6000/di pro sl detector so for now building goes to background.

Solved problem with half device working too. Just need few hours for testing new coil.
Weather is bad for 10 days now.
Coil is hot glued and fitted in ABS - votage is about 1.4mV ... got silver and rejects foil and ferrite.
I don't have epoxy but will use polyester resin.