Falcon MD20

[Noro]

Tnx! WM6!

[bernte_one]

ok, now only to solve all the Settings on the trimmers and we can start

[WM6]

Try this:

[Noro]

sry ...vco for audio tone output

[Noro]

Thank you for your help everyone.
Qiaozhi, the picture appears a 4-pin chip.
jtz54 it says it is 555 or similar (written 555 shown in picture).
I suppose it is a VCO 555
We begin with the first version and will communicate the results ... I hope to get

[Qiaozhi]

I have this stuff.

Apparently there's a newer version that includes a 555 timer.

[homefire]

I have this stuff.

[Qiaozhi]

Noro did mean new version, with NE555.

Thanks - I didn't realise there was a newer version.
That's all I have anyway.

[Geo]

It would be easy to make a schematic from the pcb (reverse engineering) but we need the components values.

[kt315]

Noro did mean new version, with NE555.

[Qiaozhi]

Hi Jtz54 ! or another member of this forum!
I want to building this metal detector but, I do not have
schematic falcon md with CI 555.
Tnx Noro.

This is all I have by way of a schematic. It's a bit fuzzy, but readable.

[Noro]

Hi Jtz54 ! or another member of this forum!
I want to building this metal detector but, I do not have
schematic falcon md with CI 555.
Tnx Noro.

[jtz54]

After replacing the ceramic caps with poly ones I played around with the tuning. The two pots can be adjusted for better deth (in my case about 50% more) but at the expense of stability. I found it possible to adjust for maximum depth then back off slightly for stability. There can be a wide difference in depth between units with the same piece of gold.

[frankly]

Is anybody currently working on this project? Was anybody able to increase depth?

[jtz54]

Over the last week I've had the opportunity to play with several MD20s. From one that is about 3 years old to a current production one. The one I've been playing with and a current one are the same. I replaced all my ceramic caps with poly ones but I've noticed the two in the front end are already poly. I've concluded that these are probably the critical ones and are in there for stability. Between mine and a current one there is little difference in thermal stability whereas the older one drifts quite a bit. Also the older probe and the newest ones are not compatible which tells me they changed the inductance on the probe. With my cheap LC meter I measured about 300uh on the current ones. The detection distance on a 1 grain piece of gold between the newest and older model is about 50%. I think they have improved the basic design and is probably as good as it get without a redesign. For what I use the Falcon for (detecting gold inside rocks not visible on the outside) I think this is an invaluable tool.