Vallon VMH3CS Mine Detector

[greylourie]

Does anyone have pinout information for the "serial interface", for connection to a laptop ?

[Phiphi]

I have bought a Vallon VMH3CS on eBay on a UK site for 185 £ + 25 £ shipping in France.
I received it today and it's seems to work but I hadn't time to use it very much.
The serial plate is missing but there is a punched tag with 6 and 10 removed so it must be June 2010.
It has pinpointing as Eric's one.
I have measured the coil inductance and found the same value than Eric : 1.5 mH and 3.7 ohms resistance. I'll try to measure soon the self resonance frequency.
I don't have a complete manual but just two plasticised papers with very basic instructions to use it.

What are the tests to do to be sure it works fine ?

[kt315]

http://www.head-fi.org/t/316937/fake-opa627s-in-the-wild/165

post #177 is there a way to check genuine vs fake -?

[ivconic]

https://en.wikipedia.org/wiki/Dichloromethane

[kt315]

Plastic one was dissolved in acid

while some geotechers do not able delete chinese snot in the coils LOL! good pro autopsy

Good thing that they did not used something like LM358

have to read BB sign on the chip first!

[ivconic]

Little off topic but i think is good to be mentioned here.
Just as Eric mentioned OPA627; i searched the Internet and coincidently i stumbled on this:
http://zeptobars.com/en/read/OPA627-...ake-china-ebay

"...Being a SOIC on a crowded board, that might be a bit tricky..."

Think twice!

"...Manufacturer (Texas Instruments / Burr Brown) sells them 16-80$ each (depending on package & options) while on ebay it's cost was 2.7$, shipping included..."

"...It does not seems they earned alot of money here - it's more of an economic sabotage..."

[Mechanic]

There are currently 6 Vallon VMH3CS detectors on UK eBay at the moment. This one has a broken arm cup, and the lowest price ->
http://www.ebay.co.uk/itm/1320091456...%3AMEBIDX%3AIT

Damn it, they don't ship to Aus
I think one of these would make a cool play toy!

[Qiaozhi]

I have made some ergonomic improvements to the VMH3CS in the form of a proprietory armcup and a clip-on ground stand. The original 'rabbit eared' armcup base was retained, but with a small amount of machining, to fit the new stronger and better looking one. A 8mm nylon bolt was also fitted to lock it into place and stop the tendancy to slide up or down the battery tube, as it did previously.

Another useful bit of information is that I think I have identified the preamp chip in the electronics. It is a TI OPA627AU which described is a very low noise precision high speed Difet opamp. I look forward to getting a scope on the output sometime soon. Being a SOIC on a crowded board, that might be a bit tricky.

Eric.

There are currently 6 Vallon VMH3CS detectors on UK eBay at the moment. This one has a broken arm cup, and the lowest price ->

http://www.ebay.co.uk/itm/132009145600?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

[daverave]

I have made some ergonomic improvements to the VMH3CS in the form of a proprietory armcup and a clip-on ground stand. The original 'rabbit eared' armcup base was retained, but with a small amount of machining, to fit the new stronger and better looking one. A 8mm nylon bolt was also fitted to lock it into place and stop the tendancy to slide up or down the battery tube, as it did previously.

Another useful bit of information is that I think I have identified the preamp chip in the electronics. It is a TI OPA627AU which described is a very low noise precision high speed Difet opamp. I look forward to getting a scope on the output sometime soon. Being a SOIC on a crowded board, that might be a bit tricky.

Eric.

[ATTACH]37940[/ATTACH] [ATTACH]37941[/ATTACH]

very nice improvements to the vallon

[tifred]

Hello Eric

It is a very nice work!

Fred

[Ferric Toes]

I have made some ergonomic improvements to the VMH3CS in the form of a proprietory armcup and a clip-on ground stand. The original 'rabbit eared' armcup base was retained, but with a small amount of machining, to fit the new stronger and better looking one. A 8mm nylon bolt was also fitted to lock it into place and stop the tendancy to slide up or down the battery tube, as it did previously.

Another useful bit of information is that I think I have identified the preamp chip in the electronics. It is a TI OPA627AU which described is a very low noise precision high speed Difet opamp. I look forward to getting a scope on the output sometime soon. Being a SOIC on a crowded board, that might be a bit tricky.

Eric.

[Ferric Toes]

Hi Eric...Tried several times to send you a message to your inbox but message came up saying your mail box full and need to delete some mail before i can send to you.

Hi Dave,
I have deleted some messages, so try again.

Eric.

[daverave]

Hi Eric...Tried several times to send you a message to your inbox but message came up saying your mail box full and need to delete some mail before i can send to you.

[Ferric Toes]

Previous excerpts:

I think I have too! Plus I think I have found the use for 2 of the 4 MOSFETS... like maybe disconnecting virtual ground from the coil and kickstart capacitor during flyback, breaking the damping R path and providing voltage doubling charge to the kickstart capacitor while it is de-referenced from virtual ground... Plus, I think I am missing about 3 ohms (remember 6 Volts at 1 amp) in the TX coil to virtual ground (probably in the flyback ground de-referencing MOSFETS)... I need to do some modeling!!! Any chance you can read the P/N of the MOSFETS?

Mosfets are 4 x IRF320 with 4 more on underside in almost the same position. I can't see the P/N so they may be a complementary type. There is only about 1/4 space between the two boards which I cannot part without breaking a lot of connections.

Eric.

[daverave]

i used a buck voltage converter in one of my metal detectors and it works very well.