Compass Liberty 150

[dbanner]

Can someone please re-post this schematic, I can't find it anywhere, but I know one exist drawn by William Lhar.

[ivconic]

[ivconic]

https://static.secure.website/wscfus...CO1991_Cat.pdf

[ivconic]

Model 50... funny enough: https://youtu.be/3irKo7UH9oE?si=OBJm8fdpqzpySrLm

[dbanner]

Thank you very much!

[ivconic]

Np.
If you figure out the coil specs; let us know here.
It is interesting design.
I am also pretty enthusiastic upon such old design.

[DavidB]

I played with this one a lot. The filters are narrow and they ring. They added a peak detector to shut down the signal quickly so you don't hear the long smear. Ancient regulator design using an LED for the current source. Half of the 5532 is used in the regulator so the pre-amp half is also full battery voltage. I literally modified one on these to death.

[dbanner]

Np.
If you figure out the coil specs; let us know here.
It is interesting design.
I am also pretty enthusiastic upon such old design.

It uses the same coils as the compass xp series/coin scanner detectors. The data for those coils are well known.

[dbanner]

I played with this one a lot. The filters are narrow and they ring. They added a peak detector to shut down the signal quickly so you don't hear the long smear. Ancient regulator design using an LED for the current source. Half of the 5532 is used in the regulator so the pre-amp half is also full battery voltage. I literally modified one on these to death.

I was interested in the U2(4066) implementation for audio at the back end, as a way of utilizing the 2 extra switches. This circuit has no comparator IC's and uses just 6 chips.

The demod switching drive circuit could be replaced with dual comparator chip(LM393), just cut and paste the xp350 circuit for the Tx oscillator and phase shifters.(If I remember right)

[dbanner]

DavidB, so it was you. Large parts of the two circuits are identical.

[dbanner]

coil specs

[dbanner]

If I were to eliminate these offset trimmers, which op amp would you recommend? Any suggestions?

[DavidB]

The main reason you need the offset trimmers is because of the peak detector or so called vari filter. It requires the levels be adjusted just right along with the peak detector. If you live in an area with decent soil you can reduce the Q of the last filter by jumping out the .22 uf which goes to gnd or what they call +3v. on the last 2 filters. Then you can eliminate the peak detector because the filters will no longer ring. Yes I have replaced those op amps with regular comparators also. I would not build this circuit because it is much easier to design something better. When I look at what I would change it ends up being just about everything.

[dbanner]

You are right.