MINELAB F1A4 ex military metal detectors - tips, settings, questions

[Eski]

Good Times!
$1200 for an L3 is the bomb... Argh, too many detactors and no time!

 

[AuMan]

Good Times!
$1200 for an L3 is the bomb... Argh, too many detactors and no time!

Tell me about it!!
And then when you do have time it is 40c or raining!

 

[Gunsmith]

Hi guys Where can I find a schematic drawing to do the gain and tone mods to my f1a4? I reckon I'll be able to do the mods myself just need to see where to add the bit's, thanks

 

[AuMan]

Hi guys Where can I find a schematic drawing to do the gain and tone mods to my f1a4? I reckon I'll be able to do the mods myself just need to see where to add the bit's, thanks

The tone is quite simple, there is a lone trimmer on the audio board. Use a 50 or 100k pot in its place.
The gain however is done on a double sided 4 layer board that gets attached to the main board along with a bunch of other stuff on the main board to make it work properly.
Sorry, no schematics, secret herbs and spices

You might find some drawings scattered across the net, but they are full of errors. Proceed at your own risk..

AuMan

 

[AuMan]

The other thing to keep in mind is the make up of the nugget.

If it is solid, that is one thing, but if it is prickly with lots of folds and fine detail its detection distance will actually be a lot less than expected.

A customer in the US found a sweet specimen last year and left it in acid. It contains about 61g of gold, but was found at about an inch.
A gpx gives no response, the f1a4 L3 and sdc gave a response, but only at about an inch.

I will ask if I can post the photo, it is a really beautiful specimen.

AuMan

 

[Firey10_0]

Hi eski and others
Thanks again for the advice, I definitely give it a try and post up my results.
I do have a DD coil, but I haven't used it since I upgraded to level 3. Are they better to use? I didn't think they were as sensitive to small nuggets as the mono's were.
Let me know.
Cheers
Firey10_0

 

[Ded Driver]

Hi Muk,

PM sent.

Eski, these F1's still amaze me!
Was testing out a modded(by someone else) 45 that was sent to me for repair.
After the repair and some adjustments, the 45 was running quite nicely, however, the f1 level 3 still had it over the 45 for ground handling, sensitivity to smalls and depth on the bigger target, without fiddling with settings.
Your extreme should not be too far off now
AuMan

AuMan, just a query.
in your opinion, what can the 4500 do better than the F1a4-L3 ?
If the F1 is better on ground, sensitivity on small, & depth on bigger targets why bother with a 4500 ?
Im asking as I am considering a 4500 sometime in the near future
DED

 

[AuMan]

And here is the 68g specci that is only detectable at about 1 inch with an F1 L3 or SDC. No response from a 4500.

 

[AuMan]

Hi Ded,

The 45 does have more timings to begin with.
When cranked right up, it is pretty good with the sensitivity to smalls.
You have options such as the stabilizer, back end gain, manual tune and different audio modes such as quiet.
Personally I'd probably go for the 5k over the 45 as there are some differences that will allow it to handle hot ground at higher gain(front end) than the 45 will. However the price of 2nd hand 5's is a bit more expensive.

You need one of each!
An alternative to the f1 L3 is a 2200 that is done up properly.

AuMan

 

[Ded Driver]

cheers AuMan.
hopefully then the SD2100 you are 'tweaking' for me will come in close to the f1/L3 & 2200
My thought was to get a 4500 sometime as an 'allrounder' to improve on the old 4000 i have, although that machine runs sweet as, with the right coil to suit conditions.
now im wondering if the tweaked 2100 will beat the 4000 on both small & depth. will be interesting to compare.

 

[Gunsmith]

Hi guys Where can I find a schematic drawing to do the gain and tone mods to my f1a4? I reckon I'll be able to do the mods myself just need to see where to add the bit's, thanks

The tone is quite simple, there is a lone trimmer on the audio board. Use a 50 or 100k pot in its place.
The gain however is done on a double sided 4 layer board that gets attached to the main board along with a bunch of other stuff on the main board to make it work properly.
Sorry, no schematics, secret herbs and spices

You might find some drawings scattered across the net, but they are full of errors. Proceed at your own risk..

AuMan

Haha understood I remember seeing a photo on this post with a pot carrying two resistors to replace one on the board for a gain mod apparently what would that actually do if it was done? Thanks auman :Y:

 

[Firey10_0]

Wow, that's amazing, how is it that a gpx4500 can't detect that at 1inch under? It certainly says how good the f1 L3 really is!!!

 

[Ded Driver]

wow that speci is fantastic. lucky bugga that picked that up :goldnugget: :Y:

 

[AuMan]

Hi guys Where can I find a schematic drawing to do the gain and tone mods to my f1a4? I reckon I'll be able to do the mods myself just need to see where to add the bit's, thanks

The tone is quite simple, there is a lone trimmer on the audio board. Use a 50 or 100k pot in its place.
The gain however is done on a double sided 4 layer board that gets attached to the main board along with a bunch of other stuff on the main board to make it work properly.
Sorry, no schematics, secret herbs and spices

You might find some drawings scattered across the net, but they are full of errors. Proceed at your own risk..

AuMan

Haha understood I remember seeing a photo on this post with a pot carrying two resistors to replace one on the board for a gain mod apparently what would that actually do if it was done? Thanks auman :Y:

I think that may have been similar to the gain in the level 2.
It works, but ground balance can be a problem in hotter ground.
The level 3 has a very different gain mod, with a host of other things done to minimize the ground balance problems that came to light in the level 2.

AuMan

 

[AuMan]

Wow, that's amazing, how is it that a gpx4500 can't detect that at 1inch under? It certainly says how good the f1 L3 really is!!!

The 4500 could not detect it at all!
It is because the specimen is not solid. There are so many fine individual details(and conductors).
The eddy currents induced into it would decay extremely fast, too fast for a standard 4500 to pick up. Also some of the eddy currents would cancel others reducing the response further(Try detecting a 1" piece of wire, then fold it in half and try again).
A VLF would scream on that piece, however, I don't think he was able to work that ground with a vlf(he does use a vlf too).

AuMan

 

[Gunsmith]

Awesome thanks for the info auman, do you have a place to contact you to mod a machine for me in the future?

 

[Marauder]

Hi GUys, not trying to hijack the thread but i've got an F1A4, which i have done the coil adaptor replacement on, and shortly will do the headphones.(level 1 mod?)

Anyway, i'm running an 11" mono commander, and it seems to run ok.

What sort of depths have you achieved? Is the level 3 mod(tuning balance and what not) worth while? Given that this detector was designed to work well out of the box, without any fiddling. I can imagine that you could do all the mods and have the settings and the coils all out of wack and be far worse than the un modded unit? Any thoughts?

 

[ironrock]

AuMan;, i dont own a 4500 but i find it hard to believe even to the point of being ridiculous that this machine would`nt even make the slightest murmur on such a decent sized piece, okay it`s a specimen, but i think the machine should be able to see the whole piece as one big lump, it should don`t you think?, i`m not trying to start an argument here, it just seems crazy that it cant hear it, i know these machines can pick up half gram nuggets at upto 14in depth and not be able to even hear such a big lump has left me gobsmacked.
If this is a common occurrence with specimen nuggets then i guess it gives us hope that there are still many chunks to find, but then the question remains, how do we find these bit`s?, most likely have to wait for better technology!!!!!

 

[Gunsmith]

So I did the L2 gain mod and the first pot and resistor set must have been faulty cause it went full ape sh#t when you adjusted the resistance up and down, second pot and resistors works a treat blanks out on a 0.13 nugg at it's maximum resistance or minimum gain still fairly stable but it's always been chattery at home as there's 1 lot of 3 phase power lines on one side and another lot of 2 phase running the other side not to mention the electric fence :lol:
Will test it out in the stomping ground this weekend thanks for your help auman :Y:

 

[AuMan]

Hi GUys, not trying to hijack the thread but i've got an F1A4, which i have done the coil adaptor replacement on, and shortly will do the headphones.(level 1 mod?)

Anyway, i'm running an 11" mono commander, and it seems to run ok.

What sort of depths have you achieved? Is the level 3 mod(tuning balance and what not) worth while? Given that this detector was designed to work well out of the box, without any fiddling. I can imagine that you could do all the mods and have the settings and the coils all out of wack and be far worse than the un modded unit? Any thoughts?

All of the mods can be turned back to their standard settings, so if it all turns to crap, you can go back to standard and work your way up from there.
As for depths, it is hard to quantify. There is a real improvement and it will amaze you at the depths the little tiniest bits can be pulled from. One spot I use for testing, I had cleaned out to the point I was only finding a piece or 2, went there while testing the early level 3 mods and was pulling bits out like I had never been there and each time I was surprised at the depth the little were coming from, and that I had missed them in the past.

Level 1 was coil plug, headphone plug, threshold and volume.

AuMan