Help with TGSL Disc and GEB Phasing

[Silver Dollar]

I built a TGSL and it was working fine. I modded the heck out of it then decided to
put it back to stock. There were cuts and removed components. I believe I have it
back to original but I'm having trouble with the Disc and GEB phasing. It looks to be
90 degrees off or something. I checked and rechecked everything in that circuit but
am at a loss for what is wrong. Can anyone point me in the right direction?

I have a scope and other equipment needed for troubleshooting. Here is the pictures
of the current operation;

[Silver Dollar]

So this is my problem. The original Disc and GEB were like this;


But now no matter what I do they are like this;


I've changed the caps and opamp and even tried changing the transistor in the oscillator.
I haven't tried the LM393 but might do that next......

[Davor]

They seem to be in counterphase, but they also seem to be toggling at correct phases.

[porkluvr]

I think you may have reversed the two outer wires going to the DISC pot.

As you rotate pot from CCW to CW, the disc clock pulse should be moving from left to right.

[Silver Dollar]

I just realized the original pictures were with a homemade DD coil and the new ones are with the original
Bandito Coil I just got which is concentric. The GEB still doesn't seem to reach far enough but I have to get
rid of my other problem of a 102 hz oscillation appearing until the board is pressed on first...

[Silver Dollar]

Well I fixed that problem but now I have low air range it's 4" on a gold Ring and 6" on Silver....

[golfnut]

Try adding a couple on nF to the Rx coil, and see iff you get more preamp output, keep invreasing or decreasing to get more preamp out put and the phase relation will alter WRT tx too.

When you can get ferrite quiet on your geb control you should be good. i.e. more sens and good phasing

[paku]

Try adding a couple on nF to the Rx coil, and see iff you get more preamp output, keep invreasing or decreasing to get more preamp out put and the phase relation will alter WRT tx too.

When you can get ferrite quiet on your geb control you should be good. i.e. more sens and good phasing

what caps 15+15nf

[golfnut]

your design will have a nominal cap value... adjust it higher or lower and see if it improves.

There is no predetermined value to try as everyones coil is different.


If I end up on this condition, i.e. no freedom to move the phasing with coil position, I have had success using a multiple switch box.


I have 1n, 2n2, 4n7, 6n8, 10n arranged on switches so I can get 1n thru to ~25n

I normally try with 1 or 2 nF addition -- if not enough phase change I add more. I often watch the phase change on scope too.

You may be able to tweak phasing like this, If at the start you have real good air sens but no ferrite reject - with these changes you can get good ferrite reject and ok sens.


You may try reducing the Rx cap value also if you cant hit a good spot where you reject ferrite, accept all wanted alloys and reject iron