1st impressions w/ GB'd Cibola. I welcome any info ;-)

[digitaltim]

Just did the mod today and I took it out on the front lawn (in the dark) to test it out.

Gb'd very quickly in AM with the 10 turn pot.

I then tried the "power balance" in discriminate mode, but could not get a beep on the up bob....I attempted it a few times, but never got it....short on time and anxious to get going I moved on with a neutral Gb in AM / then switched to discriminate mode.

I've searched the front yard a few times recently with only this cibola (unmodified) and easily found some clad. Now while modified + Gb'd I went over the same area and didn't find anything new.

What I did notice is some falsing / unrepeatable signals. I rechecked the Gb and lowered sensitivity.this helped a bit... there was lots of noise almost every where in the form of whispers and blips, but nothing that really said, "dig me."

At this point I'm not sure 'neutral' Gb in all metal is ideal, but its tolerable. <---this is where I welcome the info ;-)......I think it was Sven that said to Gb to neutral then turn it slightly positive in AM, but I'm not sure how that translates when in discriminate mode.

I have a section of the front lawn (maybe 1/8 acre), that I never searched previously.......I decided to end my night there. I re G -balanced (just to be sure) and heard whispers....I skipped over these, but I want to mention that I did not notice whispers like this with the unmodified Cibola ....I decided to stick to the pronounced tones ...with in 2 minutes I found a penny and a bottle cap that gave nice smooth tones ..after those 2 quick finds I called it a night.

What do you make of these whispers? I guess I need to dig them to find out.....I think they're just minerals ....

Any suggestions for silencing the search? Its a much noisier machine now....reminds me of the Tejon....I'm not sure if I should use my discretion more (just decide what to dig based on sound + area) or Gb the machine differently...maybe more positive? and try to quiet it down...

I think I just need more time with it....

HH.

-Tim

 

[tvr]

After being pretty thick about what was going on and finally figuring it out after re-reading some old posts that I had saved, I learned with the Tejon that when it got real chatty, going slightly to the positive of where I was at on GB made it much quieter and I could hear targets deeper.

With the GB Mod Cibola I have, with it at neutral, it is pretty quiet. Yours may react slightly differently. I'd try digging some of those whispers and if convinced they are false indications, go a little positive on the ground balance.
tvr

 

[Brokensignal]

It will most likely be noisier due to it is more sensitive all the way around.Did you use the pinpoint button wires to get a all-metal-mode.About the faint signals that is for you to figure out.I hunt different than most people on this forum,i hunt with high disc setting just were the pull tabs break out because every were i hunt is loaded with them,i miss a few nickles and small rings but i know when i have a faint signal like the one you are describing it could be a good deep coin or relic (button) type signal.If you guy's would just buy a metal detector with manual ground balance you would not have to rebuild your detectors.I am not touching mine,i just ruined a 5.75 concentric coil because i thought i was smart enough to work on it.Thank god i just got a 10"x5" elliptical i like more because i cried for two day's.Good luck with your modified Cibola.It really sounds like you might be on your way to building metal detectors.

 

[digitaltim]

n/t

 

[digitaltim]

its fun to tinker....I had to sell a ton of stuff just to afford the used cibola...my job cut my pay by nearly $200 a week (company wide cut)...so its been a year of slight adjustments ;-)

anyways.....its just as fun for me to learn about the machines as it is to use them...So I've tried many, but since this year is tough I have to do things differently

if I could have afforded one with gb I would have bought a Vaquero (again) ...and now I'm thinking a 10 turn pot would have to go in the vaq ;-)

so I've spent $250 (sold 4 things) and have a decent machine w/ Gb...

HH

 

[Sven]

could be a bunch of hot rocks. When I lived in Georgia, found several school grounds loaded with small hot rocks, by tuning positive, the Cibola became quiet.
Your sensitivity could also been a little high as well as too negative. When tuned properly, it should be stable and will be a joy to use.

 

[digitaltim]

my yard is just buried rocks, lots of granite........every area that wasn't seeded for grass is littered with rocks.

 

[Monte]

Just did the mod today and I took it out on the front lawn (in the dark) to test it out.

Gb'd very quickly in AM with the 10 turn pot.

I then tried the "power balance" in discriminate mode, but could not get a beep on the up bob....I attempted it a few times, but never got it....short on time and anxious to get going I moved on with a neutral Gb in AM / then switched to discriminate mode.

Through the years I have seen and handled a number of modified detectors. The Classic series that Mr. Bill has modified and a Gold Mountain Technologies GMT-1650 a friend modified worked beautifully. I've worked with several factory prototype units from a few manufacturers that worked great, and some that needed a little attention. Overall, however, I have found that quite a few modifications (too many) often fall short of the desired performance, or actually limit a models functions.

Ground Balance modifications have been the #1 let-down for me when I have handled these home-modded units, and here's why.

The particular component used was not of the proper type for the modification. When it comes to Tesoro's designs, I have always felt that the Ground Balance circuitry could use the most attention. Now, I am not the electronic technician I wish I was so I can't quote the proper lingo, but when it comes to selecting potentiometers for such jobs, there are linear and ... something else.

The problem or issue I have had with Tesoro's, and really most competitors brands, is that those with an internal GB trimmer seem to have a very coarse adjustment that spans a very, very wide adjustment range. All that's needed is a Ground Balance control and circuitry that addresses just the main range of ground mineral signals we will generally encounter. Because the trimmers are so coarse, tweaking them can be a bit touchy.

What would be ideal is to have an external Manual GB control tied in with an internal GB trimmer. That way you can trim up the adjustment internally to get it as close to neutral as possible, and use the external GB control to "fine tune" the GB adjustment.

By your statement that you could not get the Power Balancing to 'beep' on the up-loft of the search coil, it suggests the following:

a.. You were over very mild-to-neutral ground, such as a neutral Florida beach or a deep layer of wood-chips in a playground, or something similar.

and/or

b.. You had the Discrimination level set too high and not at a minimum setting as I suggest for efficient Power Balancing in the motion Disc. mode.

an/or

c.. You didn't adjust the GB control fully counter-clockwise (negative) enough to achieve a negative GB in the Discriminate mode.

and/or

d.. The particular 10-turn component you chose to use is not the proper type and, even though a physical 10-turn type, is doesn't really cover the full range of adjustment to match the circuitry.

I've searched the front yard a few times recently with only this cibola (unmodified) and easily found some clad. Now while modified + Gb'd I went over the same area and didn't find anything new.

You either didn't sweep over a good target this time, or you did a decent job of covering the area in the past. Probably no reflection on your modification, just on your efforts beofre.

What I did notice is some falsing / unrepeatable signals. I rechecked the Gb and lowered sensitivity.this helped a bit... there was lots of noise almost every where in the form of whispers and blips, but nothing that really said, "dig me."

Could be several things, but if not from outside EMI then from running a little too sensitive and/or rocks (intense mineral bodies) or rejected trash (often iron) in the area. Did you check them in the All Metal pinpoint mode?

At this point I'm not sure 'neutral' Gb in all metal is ideal, but its tolerable. <---this is where I welcome the info ;-)......I think it was Sven that said to Gb to neutral then turn it slightly positive in AM, but I'm not sure how that translates when in discriminate mode.

With most tesoro's I have found that a best-functional GB in the Discriminate mode (achieved by Power Balancing) results in a rather negative GB in the All Metal/Pinpoint mode. The reverse tends to be true as well, that a spot-on to slightly positive GB in All Metal results in a more positive GB in the silent-search Discriminate mode. Most people don't/can't understand this because they just don't understand Ground Balance or the fact that they can't hear anything in the Discriminate mode.

If you have a proper 10-turn GB control, and if it spanned the full range of the internal trimmer you by-passed, then you should be able to balance over mineralized ground so that it is very posiitive or very negative, just like the GB trimmer did. If you can not adjust through the full tange of the internal trimmer, then even though you have a multi-turn pot, the modification isn't up to full performance potential.

Just my opinions.

Monte

 

[digitaltim]

here's the pot I used: Mouser Part #: 652-3540S-1-503L
http://www.mouser.com/ProductDetail/Bourns/3540S-1-503L/?qs=v8eK7PNYWrvZdWZgRONwJg%3d%3d

I just followed Sven's directions.......I'm an electronics tech, but I'm not an engineer ;-) .... the mod is a very simple install. Honestly, the hardest part for me was cutting the tiny original pot off the board.

I need more time to experiment.....It was night / dark and I just wanted to try out the detector ASAP....thus the 1st impression. I only used it for 30mins ....I didn't expect to find anything in the previously searched area. The 2 targets in the second area confirmed to me that it is very capable ;-)

During my brief attempt to power balance disc was set to fully counterclockwise, but I'm not sure I had the Gb fully counterclockwise....I had set GB neutral in all metal then tried to power balance just to try it out. I did swing the Gb knob counterclockwise a few turns expecting to hear it beep, but didn't. I will try again when I have the time and report again.

Thanks for your input Monte..... I appreciate it

 

[digitaltim]

got the kids out of their baths, handed them over to momma, and took the dog + cibola out real quick..... not much time, but I'm anxious....

So this time I went to the back yard......went to all metal, set the thresh, switched to Disc mode, turned Gb completely counterclockwise, disc to minimum, sensitivity almost maxed..... I got tone on the down and up bob...I stopped turning the gb clockwise when the up bob just stopped giving a tone.

just to see.....I switched to AM and bobbed the detector there's a smooth tone on the down bob which just nulls as the coil reaches the ground and a slight increase in tone on the up bob.....

switched back to disc, lowered sensitivity slightly, turned up thresh, and the detector runs smooth and silent ...end test

I'm hoping to take it out to my hunting grounds tomorrow