How to Extend The Ground Balance on Silver Saber For Wet Beach

[bbsailor]

Does anyone have any ideas about how to extend the ground balance on the recent schematic of the Silver Saber. I have the new Eldorado and want to see if I can transfer the advice I get to the Eldorado.

One thing I have noted is that the GB control on the Eldoradois 50K pot and it is at the maximum resistance when the pot is in the full counterclockwise position or when I get closer to the wet salt beach sand and try to balance. I was hoping that by possibly making the pot value larger, by putting a series 47K resistor would help, but I still need a more adjustment control to balance it out on wet sand.

I assume that wet salt is close to the ground balance range and it can be neutralized by some circuit adjustment. I anticipate that someone may be able to help me make the modification or tell me that I am "all wet" (pun intended).

Thanks

bbsailor

[Dave J.]

Re: How to Extend The Ground Balance on Silver Saber For Wet Beach

Whether or not you can extend the ground balance all the way to salt by adding resistance, depends on the circuit topology. With most circuits, you can't.

Don't know specifically about Silver Sabre/El Dorado, but would guess they're in the "can't do it that way" category. However, chances are that you could splice something on, that would do the trick.

--Dave J.

[bbsailor]

Re: How to Extend The Ground Balance on Silver Saber For Wet Beach

Dave,

What do you mean by splice something on? Am I right to assume it would need to add some phase shift?

bbailor

[Peter Jones]

Re: How to Extend The Ground Balance on Silver Saber For Wet Beach

I am by no stretch of the imagination an expert , but here's a couple of suggestions ,
How about trying a double-ganged pot in series with itself ? ; maybe with a reduction drive to permit fine tuning.
I am not sure about this but do not machines with "salt" mode also reduce sensitivity for wet sand ?
I am sure I will be corrected if my suggestions are not correct. Good luck if you try modding your detector.

[bbsailor]

Re: How to Extend The Ground Balance on Silver Saber For Wet Beach

It is not a matter of getting finer control. I added a 47k resistor in series with the 50K 3 3/4 turn pot and that is still not enough to extend the GB to the wet salt sand on NJ beaches. With the added 47K series resistor, I was able to get a little closer to the wet sand but I'm not shure if continuting to increase the resistance is going to do the trick?

I'll welcome any ideas.

bbsailor

[Dave J.]

Re: How to Extend The Ground Balance on Silver Saber For Wet Beach

Without having the circuit, this is just a guess, but.... where the 47K fixed resistor and the 50K potentiometer come together, try adding a .001 capacitor to ground and see if that get you any closer. If it helps, but isn't far enough, try going to .0022.

--Dave J.

[BJ]

Re: How to Extend The Ground Balance on Silver Saber For Wet Beach

Invert the signal at the output from the
comparator,this way you will possibly get
at the wet sand from the other phase pie
field. If the SS can shift 0-180deg it
will enable you to go from 180 to 360deg
(if the SS sweep the phase this broad?).

Otherwise change the capacitor value on the
input of the comparators.It would give you different phase start points.

REg
BJ

[Sean Goddard]

Re: How to Extend The Ground Balance on Silver Saber For Wet Beach

Your right Dave!

I've run some circuit similations in PSPICE on this mod you suggested, and it does appear in principle to give the required phase shift for "typical" wet sand.

It's not perfect, but should do the job.

I've been experimenting with similar mods myself, and found that you could go mad and change the 50K to a 500K witha 10:1 reduction drive, or just simple use a 10 turn pot (BOURNS) although not an elegant solution, it does work. Trouble is, it's on an exponential curve, whereby after a certain point, the resistance has NO effect at all.

The typical law of diminishing returns I guess.

[Edwin J. Fowler]

Re: How to Extend The Ground Balance on Silver Saber For Wet Beach

correct me if I'm wrong. when attempting to GB on wet sand, you always get a POS response? Even with the GB-pot all the way counter-clockwise.

So where is the failure in adding more resistance in line, on using another, maybe 500k pot in series? Why is there a need for a CAP?

Please explain.

thanks

[nikki fowler]

Re: How to Extend The Ground Balance on Silver Saber For Wet Beach

I don't mean to beat a dead horse on this, and I am a little late also. I hope someone can clarify something. On previous post on this topic, there was an addition of a 47K resisitor. Also an addition of a Capacitor. If the original 50K pot was "replaced" with a 250k, 5-turn pot, would that be sufficient, or would there still need to be a Capacitor placed? I hope someone reads this as this is a pretty old one. Thanks

[Siliquae_Sid]

Time to shoot the horse here.

I've tried all the above mods and NONE WORK. Simple reason? When you alter the GEB on a Silver Sabre, you alter the DISC setting too .

It's a quirk of what is, although a very effective machine, a poor design. what Tesoro's system does is move the ground reference point for the discriminate circuit as well.

[Goodrat]

Wet Salt

This is what I did for my Cutlaas II/Bandido machine. Basicaly it adds a resistor accross C12 and a 3900pF from the wiper of the pot to the bottom. The switch is to disable. This will shift the ground balance to salt, however, you will detect iron!