Whites Goldmaster II

[Mechanic]

Hi Guys,

I have here a Goldmaster II for repair as it was not leaving the battery test mode when turned on. I seem to have fixed that.
Now when it finishes the battery test and the needle drops back down to the "non iron" section the detector just emits a constant tone that can't be silenced no matter what I do with the controls on the front of the machine.
I don't have a coil with this machine.

What I was wondering is if someone with this machine(working of coarse!) could test their machine without the coil and see if it just emits a constant tone.

When I touch around the coil connector I can get the machine to sound off, so I am thinking that with a coil connected it might behave as it should.

Cheers Mick

[Dave J.]

Many metal detectors will do unpredictable stuff without a searchcoil plugged in. And in any case, you can't verify that a metal detector works properly without a searchcoil.

[kt315]

SOS reply

Mick, I got only ONE pic of THE board for all time i here. asking in your accistance to get more...
part list of all ICs you see inside welcomed. i ALSO need in YOUR help as you do.

cheers

my email for a contact [email protected]

[all pics from you people are accumulating in ONE archive.]

[Mechanic]

Many metal detectors will do unpredictable stuff without a searchcoil plugged in. And in any case, you can't verify that a metal detector works properly without a searchcoil.

Thanks Dave! Yes you are right. I suspect that without a coil this detector could be "receiving" an overload. With the coil on it could very well bring the rx back to the nulled/no-target state hence why I can get it to a quite spot with my finger.

KT, I will shoot you off some quick photo's, but that's it as I don't have time to waste

My advice to anyone trying to repair these, First check battery connections right down to the board, then carefully check for dry solder joints and clean up any areas that may have some corrosion.
Oh and NEVER fiddle with the trimpots unless you 100% know what it is adjusting and how to adjust it

Cheers Mick

[kt315]

O-key, Mickle. people is ordering DVD with the archive from me and they are wanting full information.
THE source of THE info is YOU there. not nobody from the whites, tesoro and etc 'experts'.
we all do OUR small deal, here. for myself.

have a nice fun times with GMII

[Mechanic]

Hi KT,

Decided I would attach the files here, that way it's free for all

Cheers Mick

[kt315]

thank you much Mick.

coil specs

[Mechanic]

Ok, coil arrived today. Found that the threshold could not be tuned out using the tune knob.
Sniffed around the board and found that one trimmer was coarse adjust for the threshold. I set this so the threshold could be set on edge in both PP and SAT modes. It is very touchy!
The detector still puts out a constant hi tone when there is no coil plugged in. When it is plugged in, the detector works fine. So I would say this is normal.
The iron reject seems to work quite well too, not a bad little detector...

I have updated the picture with a little more info for those in the future who go searching for a schematic for the GM II.


Cheers Mick

[Mechanic]

Another update...

Before sending this detector back I first cooled the board down and the problem did not reoccur.
I let the detector sit for a few days, turned it on, no problems. Sent it back to its owner.
Owner receives the detector 2 days later, I receive a phonecall.... It's still doing it! @#%&* <<< This is why I hate vlf's with no schematic or cct information to work with.

Anyway, he sent it back again. I had been a little suspicious about the regulated voltage, so first up measured the regulated voltage from the lm2931ct. This started out at about 6v and slowly rose up to 8.5v. The original problem occurred. After the voltage had reached 8.5v, turned it off and back on again. This time it started out at about 7v and once again rose up to 8.5v. This time the detector worked alright, however the threshold was not properly adjustable until the 8.5v was reached. Just to be sure, i removed the cap in the voltage feedback network for the reg and let it cool right down again. Voltage still rose up slowly. Added heat to the reg, turned it on, voltage was straight up to 8.5v and the detector ran as it should.
Just to confirm that the low voltage was causing the problem I used the special wet finger tool to adjust the reg voltage back down to 6v, turned it off and back on sure enough the problem happened. So, I have ordered another reg and when it arrives and has been installed and sat for a week I will update this thread. I am 99% sure this will fix the problem...
Did I mention I don't like fixing vlf's? Give me a ML PI with white paint and ground off part numbers any day! Hope someone finds this info useful.

Cheers Mick

[WM6]

You are best mechanic way around Mick.
Congratulations on repair and thanks for share your experience.