HI CARL? BENJI
[when I use the knobs for tuning I get a good clear response both audio and on the meter.
Everything seems fine, except I get no reaction from the coil to anything
metallic. I have tried various coils, still nothing.There just is no response. Any ideas?
A)? Am trying to get some rusty brain cells in the memory bank going.?
There were 5 knobs.?
One is for power, batt check, coil size,?a multi postion switch."ID" it and leave
it alone for the moment.
One striclty controls the position of the meter needle. "ID" it?
and? leave it alone. for the moment.
One knob controls the audio output/tone, "id" it
and leave it alone for now.
The push button restablishes your original tone setting.
The other two controls are connected to the? FET which forms? a tank circuit
of around 5 Kc. this is in turn connected to the coil with the ferrite coil.
Feed back from the coil detunes it. which results in an indication and increase in the audio.
One contols the output of the FET, the other the feed back to the FET.
So, You initialy increase the FET output with one, then bring it back
down with the other knob.? You keep doing this until you reach the point
max sensitivity/stabilization . Experiment.
I loved this old critter since it was the first that could
quasi cotrol the mineralization, liltle or no reaction with iron minerals.?
It was very senitive and the large coil was rated for 16 - 18' on a l
large target.?It came with a small nugget coil, a 7 " for general useage,
and of course the 3' one.
It was well balanced, but the large coil was unhandy in brush,
but where it could be used? (beach) it was faaaast?
?For serious treasure hunting i wouldn't hesitate to use it,
even in competition with more modern instruments, even if it is
initially a pain in ---to balance it, but once accustomed to it, no problem.
cost $900 in "those" days sheesh.
I have? a 3- D, White 800 and a Discovery 900?. twin coil units.
Somewhere I still have the hand drawn circuit , courtesy of his
design engr. will keep looking and post it.
I still have the 3 ' single turn aluminum tube coil which I adapted
for use with my Garrett PI underwater unit.? works very very nice.
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Also one of the polarity markers showing how to place the batteries is gone.
I am guessing that the batteries positive terminals are facing opposite directions.
since they are side by side one batteries positive terminal points to the right and
the other points left. Is that right?
A) NO!? if I remembe rightly they were 2 "c" cells of 1 1/2 volts, wired in parallel.
The other? "AA" battery is involved in the feed back circuit to the FET.
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I appreciate findiong some one who know wjat I am talking about when I mention "Gardiner"
Thanks for the help...
p.s. the acompanying photo shows the old flat 3' coil and "part"
of a load from "one" mule of Mexican silver 8 reales from a 9 mule
pack train which buried about 3".? Fun & kept me eating for a while.
The coil shows my winding of a a farraday shield on the coil.?
K, not too professional looking but worked? heehe.
Incidentally, all of the GARDNERS coils were of the flat pancake design.,
with the exception of the last? 3"? single alumnum tube coil.
You want the formulae of a pancake coil if you decide to wind a special coil?
If you blow the FET, it can be replaced, but the coils will then have to be rebalanced.
This is done inside of the ferrite coil unit via cap & resistors, easy if you have a freq. meter..
