Vallon VMH3CS Mine Detector

[UK Detectorist]

Hello, I have just joined this forum more so to learn about the technical side of detectors, I live in the UK near the city of Oxford and started detecting in the 1980s , I have just acquired a Valon VMH 3CS, these detectors seem to be popular with beach detecting like the C scope 4Pi , am hoping members on here can give me tips on setting up, I read you can use AA Alkaline batteries ? instead of DDs, and Vallon have an adapter to use normal headphone but won't sell to UK so is there an alternative or can one be made and what parts required, thankyou

[F117]

I would strongly advice you to read ALL 79 pages of this thread...
The most interesting information is provided by Eric Foster who initiated the thread.
To save you some time, here are some topic numbers and links that were useful for myself when I did the battery and audio mods:

Headphones:
#165, #333, #426, #450, #458, #460, #524, #543, #537,

Audio transformer:
#672, #707, #709, #769, #771,

This is the battery mod I did with 2 LiIon cells in parallel = 3.7V
https://www.geotech1.com/forums/show...100#post261100

My audio schematic:
https://www.geotech1.com/forums/showthread.php?23169-Vallon-VMH3CS-Mine-Detector&p=261240#post261240

[UK Detectorist]

Hello, thankyou for that, while I read all the info I can on the Vallon VMH 3CS I have no technical ability to do any electronic work or know what the parts are called, I can manage with the DD batteries, but it's the headphone supplied are no good due to hearing loss therefore would there be anyone on this forum could make the adapter like on the Valon web site ??????so I can use my normal detecting headphones which have a volume switch, I would be happy to pay costs, thankyou

[6666]

You can buy a variety of "D" cell converters that use AA battery's
the ones I like come with 3 battery slots but you can plug 1-2 or 3 AA's into the side
I use just 2 AA nicad battery's in each converter .

[UK Detectorist]

Hello, thankyou to reply, ok I shall check those converters out, and look for some good batteries, I read Alkaline are best but you use Nicads ???cheers

[Ferric Toes]

Hello, thankyou to reply, ok I shall check those converters out, and look for some good batteries, I read Alkaline are best but you use Nicads ???cheers

See my PM.

Eric.

[UK Detectorist]

See my PM.

Eric.

Hello, sent email Eric, cheers

[yaffle]

Hi there, Yaffle here from NL. Awesome thread that keeps on giving! Thanks for that y'all!
I have a VMH3CS incoming, as well as a Guartel MD8+. Will be interesting to see how they compare over here...
But, I read up on all the info on the headphones, and was wondering if anyone tried (building) this one?

http://makearadio.com/misc-stuff/piezophones.php

If so, is it a good fit for the Vallon?

Thanks,
Cheers,
Yaffle

[davyowens74]

Been away from the hobby for a bit and managed to lose my original profile; Really enjoying re-reading this thread along with the latest posts and have brought my detectors out of storage this week including the Vallon; looking forward to some tinkering.

[SFi]

Hi
Someone here used an tested vmh3cs would please tell me what is the maximum depth (or air test) of this device (with standard 30x17cm coil)? Not for gold nuggets or coins; I mean about big block of metal for example 10x10x10 square cm.

[Infamy]

I don't know if this has been covered, but I saw a video from Norway where the guy using a Vallon VMH3CS said the detector had discrimination but it was turn off. Is this correct?

If you can get software updates then it must be a button sequence?

[Little Tinker]

Thanks for all these posts, a great 4 day read with lots learnt.

[Little Tinker]

I must add I noticed a different behaviour that's not mention anywhere that I have read.
on huge signals where my etrac would show "overload" the vallon seems to change into pin point mode and make a different lower tone and the closer to the overload the pitch went up and the leds moved to the right.

Is this normal?
Its a nice feature but I wasn't expecting it.
On the larger plate it reads year 2011 and serial number 16859C in really great condition with both ears intact and minor scratches to a few corners.

[Little Tinker]

RIP Eric.

[F117]

Just a short update on the battery mod I did on the VMH3CS.
Instead of putting in 3x D cells in series, I made up a battery tube from a 32mm drain pipe and 2 x 18650 LiIon batteries in parallel.
No protection on the batteries - charged with an external charger.
I have 2 of these tubes and I use them alternately. This went fine for 7 years, until I dropped in one of the battery tubes upside down.


Inside the VMH3CS battery tube, there is a small recess at the positive pole side, that allows for the protruding + pole of a battery to make contact, but not the flat sided negative pole.
On my quick and dirty home made tubes, both + and - connections contain a small screw, and this screw head on the negative side was sufficient to make contact to the VMH3CS positive connection.
So, a direct connection of + and - reversed batteries without current limitation, resulting in a catastrophic failure.
Post mortem analysis: across the battery connection on the signal distribution board, there is a protection diode.



Located here:



This diode is probably perfectly capable of withstanding a D-cell reverse polarity, but was no match for this uprotected LiIon bomb.

Resulting in a burnt component and part of the PCB trace:




I contacted Vallon in Germany via email and they confirmed in a friendly reply that my assumption was correct.
In the mean time I had already replaced this destroyed component with a 1N4007 diode + some wire over the burnt trace.
After this repair, the detector was working fine again.

To avoid these kind of stupid "accidents", I built a new battery tube from a cylindrical Anker powerbank.





This delivers 5V output to the detector, resulting in a very happy beep and all LEDs lit at switch-on.





I added a small "window" in the drain tube to view the 3 LEDs during charging + an external USB-C connector.
The + and - connection of the battery and the USB-C charge port were connected with the USB cord cut in 2 pieces ( USB-A and USB-C) that was included with the powerbank.
I also tested that the 5V output is short-circuit proof.

Here is the Anker tube charging via the USB C connector --- the paint job has gone terribly wrong:




Well, lesson learned: when replacing the 3D cells with an 18650 combination, add some protection around the batteries.
Or better yet: use a cheap 5V powerbank, as suggested here in the thread already on a number of occasions.