White 3900D

[MartyJ1963]

Thanks for the files DB,,,The schematic (Cscope schematic) mentions wire size and turn numbers but not coil size,,I.E:-L1=55 Turns x 0.4mm and L2=145 turns x 0.25mm. Is there any other coil data mentioning sizes etc,,,Thanks,,Marty.

[dbanner]

Thanks for the files DB,,,The schematic (Cscope schematic) mentions wire size and turn numbers but not coil size,,I.E:-L1=55 Turns x 0.4mm and L2=145 turns x 0.25mm. Is there any other coil data mentioning sizes etc,,,Thanks,,Marty.

I know I have the coil data somewhere on my laptop.
I will have to look through some folders to find it, but I'm sure I have it somewhere. I'll post it as soon as I find it.

[MartyJ1963]

Thanks DB,,I may have a go at making this one. Which supplier do you get your NTE7144 from? I've had a look for the CA3140A but can't find any either? Thanks,,,Marty.

[dbanner]

Thanks DB,,I may have a go at making this one. Which supplier do you get your NTE7144 from? I've had a look for the CA3140A but can't find any either? Thanks,,,Marty.

There is a local agent for NTE electronics in my country.
You can check NTE website online to see nearest supplier in your area.
I don't think the CA3140 is only opamp which can be used, for example, in the Rx preamp, another opamp could be easily substituted.
For the other part of circuit (retune feedback section) I think I will have to experiment with some other opamp to see what will work. So I am not too bothered because I can get the NTE7144 from local supplier. The NTE7144 has exactly the same specs as the CA3140, it is made as a direct replacement for it. NTE specialises in making direct replacements of most popular chips.
I have used NTE chips before and my experience is that they work very good indeed.
I have found an NTE7144 in my junk box of parts, but it is with one leg broken, so maybe I can solder a new leg for this poor chip, and give it some new purpose to its existance. I also found an NTE930 in the junk box which is also a BiMOS opamp, so I can also try this one as well.
I am making PCB today.

[MartyJ1963]

Good luck with your build,,,,looking forward to seeing your results,,in the meantime I wll collect parts etc. Regards, Marty.

[dbanner]

I have come to an obstacle. I do not have enough wire for 16mH coil.
Now I have to look around the place to salvage some wire from somewhere. I have some old "big Back" TV's, I could get the wire from the degause coil or maybe from the deflection yoke.

[ivconic]

I have come to an obstacle. I do not have enough wire for 16mH coil.
Now I have to look around the place to salvage some wire from somewhere. I have some old "big Back" TV's, I could get the wire from the degause coil or maybe from the deflection yoke.

Usually it is 0.4 to 0.5mm gauge.
Not suitable for RX coil.
You better try to find some transformer to dismantle.

[dbanner]

Usually it is 0.4 to 0.5mm gauge.
Not suitable for RX coil.
You better try to find some transformer to dismantle.

You are right! I wrapped 10 turns around pencil and measured the width and divide by 10. Diameter is 0.40mm!
I have microwave oven transformers in the junk box, the secondary windings are very thin, maybe this will be good enough, but now I have to cut the core to get the wire out.
I feel like vagrant of electronics sometimes, always having to scavenge around for basic stuff. But that is the fun of poor man's hobby.

[ivconic]

You are right! I wrapped 10 turns around pencil and measured the width and divide by 10. Diameter is 0.40mm!
I have microwave oven transformers in the junk box, the secondary windings are very thin, maybe this will be good enough, but now I have to cut the core to get the wire out.
I feel like vagrant of electronics sometimes, always having to scavenge around for basic stuff. But that is the fun of poor man's hobby.

Story of my life.
Now, so many years after; even with money enough to buy material: i still find my self in a mess of dismantled devices, parts, wires etc.
I guess it becomes part of my mind, during the years. And also there is some beauty and joy in that too.
Lot of fun too!

[MartyJ1963]

Any news on progress yet DB? Can you let us know if it's worth building or not please?,,,eager to start a new project, lol. Thanks,,,Marty.

[Nandor]

Hi

Marty the is a site were I,ve found CA3140 from Intersil - try tme.eu it has 1.15 Euro price

No commercial intention just to help you

[MartyJ1963]

Hiya Nandor,,,Thank you for the information, I very much appreciate it. I have been searching for these chips to build a few other 'Old' detector projects as well as this 3900D project. Thanks again. Marty

[dbanner]

Any news on progress yet DB? Can you let us know if it's worth building or not please?,,,eager to start a new project, lol. Thanks,,,Marty.

I have made some progress, just finished winding some coils. Now I have to finish populating the PCB. Some components are still missing, like the CA3140 chip. But I will use a substitute. I hope to begin testing in earnest in a couple days.
I made simple DD coil, 8 inches in diameter. It is rough but good enough for preliminary testing.
I have no doubt that the thing will work, only question for me is what will be the discrimination. This will be the tricky part, whether or not the Rx coil is left untuned.

[MartyJ1963]

Nice to hear your progressing,Looking forward to your next posts,,,,What is the coil data for this project please? Thanks, Marty.

[MartyJ1963]

Any news yet DB?,,,It's been a while,,Lol. Regards,,,Marty