Vallon MH 1604

[Guenter]

Hi all,
I use this as a pinpointing detector, and since half a year it is unstable.
Has anybody schematics?

Thanks

Guenter

[lonelyWOLF]

hi..Guenter


here is the schematic.

I find it now. I do not know how a detector.? Share photos we...

sorry big photo


regards

Dagci,erol

[Guenter]

I do not know how a detector.? Share photos we...
Dagci,erol

Hi WOLF,
these are good news, despite the fact, that the device has repaired itself... for a moment at least. It is from the german military services. The circuit seems to be quite simple, except for the voltage stabilization, where they use 50% of the parts...I think
( I have no idea how to insert an uploaded image into the text...hopefully it works...)

Guenter

[dbanner]

Interesting schematic.

Anyone can help with how the loudspeaker is driven? The schematic is simple enough, and what that array of transistors on the far left. Can anyone offer some analysis and comments on the circuit please,. Maybe good for adaptation as a pinpointer?

[ZOUjiarui]

Hi guys, can anyone tell me what the squares in the picture represent[ATTACH]57184

[waltr]

"a b c" looks like connections to a panel mounted pot.
"d s g" is a JFET. Looks like they are only using the JFET's 'diode' (Gate to Source), hence no drain connection.
"R1 R2 R3 R4" are weird looking. Never seen that symbol. Possibly thermistors??
"LS4 LS2" also look like connections to a panel mount device, maybe a switch, maybe a pot.

No idea what the symbols near R5 are. There are notes there about 'only for 1607'

[Carl-NC]

LS1 and LS2 appear to be connection points for the speaker. I'm not sure about A-B-C, but surely another interface component, maybe the switch.
Overall this looks like an energy-theft design, which is the same method used in the Garrett pinpointers, the 1st-gen Minelabs, and the early White's Bullseye. IC1-L1 form the oscillator and D1-R12-C2 form the amplitude detector.

[Carl-NC]

"a b c" looks like connections to a panel mounted pot.
"d s g" is a JFET. Looks like they are only using the JFET's 'diode' (Gate to Source), hence no drain connection.
"R1 R2 R3 R4" are weird looking. Never seen that symbol. Possibly thermistors??
"LS4 LS2" also look like connections to a panel mount device, maybe a switch, maybe a pot.

No idea what the symbols near R5 are. There are notes there about 'only for 1607'

The JFET is being used as a diode, not sure why.
L1 is the search coil and it's shown with a shield, where the shield is grounded through R5. The squiggly lines are where a PCB trace can be cut and R771 added "for 1607".

[ZOUjiarui]

It probably uses two coils, it's not a PI.

[ZOUjiarui]

It either has a connector and uses a larger coil.