AN/PSS-12 Mine Detector Documentation

[Eclectic]

Does anyone have schematics for this unit? The search coils are starting to show up on the surplus market and look like they would be a good starting point for several types of metal detector. I think the original electronics are a PI type detector with only adjustments for sensitivity, but it's supposed to be able to pick up a small metal firing pin in an otherwise all plastic mine buried 10-15 inches. Anyone with access to the Army online technical knowlegebase should be able to retieve the maintenance documentation.

[Carl-NC]

Yes, it's a PI. Do a forum search, seems like this was discussed a year or so ago.

[Eclectic]

I didn't have much luck searching for "mine detector", "Schiebel", "pss-12", "an-12", and on google.

Operator's manual: TM 5-6665-298-10
Maintenance manual: TM 5-6665-298-23&P

Available on https://akocomm.us.army.mil, but I'm not military affiliated. I thought these were supposed to be public documents?

I'll take a lathe and milling machine to some damaged coils if I need to to see how they are constructed.

(I always U.T.F.S.E.)

[revmaster]

Hi,
Sometime back i repaired AN19/2 detectors, those are old generation PI detectors. Dont know about AN-12 but must be on same platform. I am sure you will not find much info about these on internet coz i had earlier banged my head a lot for schematics , but with board level diagonisis u can easily repair them.

[Eclectic]

The AN19/2 is Schiebel's model number for the US military AN/PSS-12. It's the same unit. I don't have the electronics boxes, just the search heads, which are well made ridgid rubberized, waterproof dual coils.

Could anyone with a US military affiliation (National Guard, reserve, family) check the AKO online documentation and see if there is a schematic in the maintenance manual?

[revmaster]

I had once broken apart An19/2 search head. Its a simple coil with Tx =250uH and Rx 450uH but they have done very good sheilding.
I believe the schematic for this unit is so complicated that one cannot build it at his home, but still you can use your existing PI detector and with some tweaking you can get farily good results, i had tried that earlier.

Moreover AN19/2 is obselete. I came across ATMID sometime back, its a very good detector unit looks same as AN19/2 but with very high sensitivity and good pin pointing capability. I didnt opned the unit but i think it is based on a different principle it works on CW instead of PI.

[Eclectic]

I don't want to copy the electronics, just use the search head with custom electronics. Do you have a pinout for the search head? Also, are the coils completely seperate? Any built in cap, resistors, bucking turns?

[revmaster]

Hi,
Search head is very simple for AN19/2 set. You have 6 pin connector 2 pins are for looping supply, one pair for Tx and other pair is for Rx. You can easily find pinout using a DMM or LCM. There are no resistors or cap in the coil. Very simple coils coz i think they had been designed about 10yrs back.

ill be out for a week if you want pinout i can email you pinouts from my office after a weeks time.

[Eclectic]

Ok, a very low tech investigation of the search head (beating it to pieces with a hammer) reveals an outer coil of 16 gauge stranded wire, an inner coil of 22 stranded, 4 leads in the cable, absolutely no shielding, no crossconections in the coils.

[Unregistered]

Have Manuals

I can send you a copy of both manuals. Send an email to steve@catholic.org and I'll send them.

I too am interested in this topic and would like to learn more about them.
Regards,
Steve

[Unregistered]

Thanks Steve. The manuals make for an interesting read. No Board level schematics though (for anyone else who might be interested).

[Max]

Have some info

Hi,
for who is interested : AN/PSS12 is the US Army designation of model AN-19/2 (Schiebel, Made in Austria).
Outer coil is for TX and inner for RX. Without revealing any secret here is some data:
- full cycle period = 293 us
- 2 TX pulses (negative and positive) duration = 120us
- TX pulses separation = 10us
- peak current in TX coil about 3 Amperes
- first delay = 10 us
- RX target sample width = 10 us
- secondary delay = 15 us
- RX "background" sample width = 200 us
- RX stage uses a level detector and two sample and hold amplifiers : one for the target signal and the other for the background (ground balancing and noise)
- RX stage uses a difference amplifier to drive the internal VCO that isn't linearly driven but has exponential response (a kind of "booster" circuit)

I don't think one can build a clone of this machine at home.
Well maybe not at home, but in the bat-cave yes

Best regards,
Max

[Max]

addendum

Just remembered that
-frequency is 67Hz (full repetition rate is about 15 ms)
-Rx-background sample extends until next TX pulse
Overall design is different from any other PI that I know expecially in the
digital sections (timings/control) and data processing (semi-analog).

Best regards,
Max

[bbsailor]

I had once broken apart An19/2 search head. Its a simple coil with Tx =250uH and Rx 450uH but they have done very good sheilding.
I believe the schematic for this unit is so complicated that one cannot build it at his home, but still you can use your existing PI detector and with some tweaking you can get farily good results, i had tried that earlier.

Moreover AN19/2 is obselete. I came across ATMID sometime back, its a very good detector unit looks same as AN19/2 but with very high sensitivity and good pin pointing capability. I didnt opned the unit but i think it is based on a different principle it works on CW instead of PI.

revmaster,

I just received 2 AN-19/2 search coils from an eBay purchase. I did a quick analysis of them and here is what I found.

TX coil wires: clear and black, 0.66 ohms, 240uH, resonates at 805kHz measured at the end of the cable.
RX coil wires : red and blue. 2.54 ohms, 453uH, resonates at 563kHz measured at the end of the cable.

I measured the coil inductance with an Extech 380193 LCR meter at both 120Hz and 1KHz with nearly the same results. I used a scope probe set on the X10 setting to minimize the scope probe capacitance loading on the coil when measuring coil self resonance.

When I wrapped my hand around either the TX or the RX coil while at the peak resonant point, the resonant frequency dropped by about 10Khz. This indicates that the coils are not shielded or are incompletely shielded such as on the bottom only.

When you took the coils apart, what type of coil shielding did you find?

Thanks

bbsailor

[Eric Foster]

Hi Joe,

I have a couple of those ebay coils, plus also a full AN19/2 kit purchased on ebay a while ago. None of the coils have internal shielding and the cable doesn't have any either. I found I had problems on a wet beach because of the capacitance effect, and also if you move the cable near to the aluminium upper stem, you get a false signal. The test pin seems to be mild steel and my Deepstar picked it up just as well with a 15uS delay. Sensitive to iron mineralised ground and with only manual zeroing it was hard to keep a threshold. Not sure I would like to go mine hunting with one, particulary for low metal mines.

Eric.