Nautilus revisited

[ranko]

Please help!!!
r75-?
c paralel with L1-?
retune taster?
sw1 and sw2 pcb conection places?

Thanks....!!!

[Skippy]

I mentioned R75 wasn't given a value, in one of my earlier posts. I think it was hard to read. Looking at the circuit for the similar Aquasound, R75 is likely to be 4.7M Ohm.

Capacitor across L1 was stated as being 15 nF.

And the two unknown 'C' capacitors will probably be 10 nF, the same as the other side of the 4016 switch. ( see the Aquasound schematic )

[kt315]

Project abandoned due to excessive price of high quality multi-turn pots.

https://www.ebay.com/itm/10K-Ohm-Pre...oAAOSwNsdXRv0c

[dbanner]

Please help!!!
r75-?
c paralel with L1-?
retune taster?
sw1 and sw2 pcb conection places?

Thanks....!!!

The switch wiring diagram is shown with color coded dots on pcb layout picture in the same post. The feedback resistor is 2.2M ohms.
Refer to post#86 for complete last schematic.
R75? Where is this resistor?
I leave the cap for L1 to set when tuning self made coil.

[dbanner]

https://www.ebay.com/itm/10K-Ohm-Pre...oAAOSwNsdXRv0c

Thanks for that. I found what I wanted salvage from old equipment. This will be long term effort, simply have too many things going on at the same time.

[dbanner]

I'm not sure if the nulling pots are multi-turn, but most likely they are. The discrim and GB pots are multi-turn.

[ranko]

r75 its paralel with autotune switch....thanks for help

[dbanner]

r75 its paralel with autotune switch....thanks for help

Ah yes, now I remember. This resistor is soldered to the switch itself but I couldn't see it clearly to determine it exact value. It would be in the megaohm range. 4.7M would be good.

[dbanner]

I have updated the schematic to properly show the red push-button tune switch and Auto Tune on/off switch. The resistor(unknown value) is now shown connected to switch the proper way from the pics I have seen.

[dbanner]

The final piece of the puzzle.
I figured out how dmc2b coil is made. It is bifilar coil same as 1260x design. Ha ha! Easy peasy. Clue was the two fine balance loops on the 2b coil photos. The center tapped TX coil needs a feedback coil for each half plus the little extra loop for final balance. Just like the 1260x coil

[dbanner]

Now I have good confidence in my ability to complete the project successfully. I begin with etching PCB tomorrow morning.

[Melbeta]

What was the frequency of this particular detector?
Melbeta

[dbanner]

The manual for the 2b states it as a 14khz machine

[dbanner]

The dmc2 coil data was put on thread by other member as TX 3.2mH 10 ohm, Rx 8.42mH 30 ohms. So I think I might be able to make a search coil. Maybe I will try simple 2D coil first

[dbanner]

The 1260x coil is good guide for how to wind turns of bifilar design. Of course new calculations will have to be made for 14khz