1978 Garrett Master Hunter VLF/TR featherweight/groundhog 15KHz tuning question

[Herb Jones]

I have this old detector that's in great shape. WhenI power it up, and tune it to a perceptible tone level, (as per the instructions), the tone volume seems to continuously creep/fade( not sure of the proper terminology) and give an ever increasing tone. Does this sound like a user /misadjustment issue or is this a mechanical issue? I bought this unit a while back and know nothing of its history, but like I mentioned previously it was literally in pristine condition, not a blemish anywhere, which leads me to believe that my idiocracy is flaring up... Any suggestions would be greatly appreciated..., and buying a new hot shot detector is out of the question, if I'm going to stick with this it'll have to be with the machines I have on hand. I simply do not have the financial resources to upgrade. I purchased this with hopes of trying to relic / cache hunting, (as of yet I am just digging coins mostly). The American S3, and Compadre are my coin machines and they both work fine for that purpose. I thank you all in advance for any knowledge you can share.

 

[straker]

Some metal detectors require you to press the button while you adjust tuning. You might want to have the tuning set to 'normal'.

 

[Herb Jones]

The featherweight I own requires exactly that, and that's how I tune it, but it just doesn't seem stable. . It seems as though once it's tunes, it begins to almost immediately progressively detune. The needle begins climbing and the tone increases. I typically need to adjust my sensitivity control to its minimum setting. As the needle climbs, I reduce sensitivity, to counteract and lower the tone... I have scoured the internet, and it almost sounds like it's the circuitry warming up, however I ensure the temp has had time to stabilize when I move the detector from one environment to the other.... but that's how it acts... like its warming up. I will probably send it off just to have it checked and rule out any mechanical issues... that way I be assured it doesnt have a bug. Gonna put a few hours on it tomorrow, to see if I can sort anything out before I do ship it off. It's probably me. I am prone to moments of dibilitating ignorance... just thought maybe I'd ask...there seems to be some wise folks loitering amongst these forums.

 

[straker]

If Garrett can't fix this...there is Keith Wills of www.brokendetector.com
He may help you out.

 

[Gene]

Probably warming up would be my guess. Going through different temperature ranges would do that.
Could even happen from going from sun to shade or shade to sun. Do you have any mineralization
that you know of ? Are you running the Groundhog in TR or VLF ? I seem to recall that there is a
detailed explanation of how to operate the Groundhog I have seen on this website somewhere.
Would be well worth the effort to find and study that. Good hunting to you !

 

[Fishers Ghost]

It is not uncommon for the Ground Hog & ground Hog A2B to drift out off tune in Manual tune mode.
If it does just flip the master tune switch to the left in Ground cancel mode for a couple of seconds and the detector will retune to you initial setting.
If in Disc mode then flip the switch to the right for a couple of seconds.
The easiest way to keep the detector in tune is to operate in Auto tune mode and the detector will keep itself tuned to you initial setting.

This may help.
http://www.garrett.com/hobbysite/hbby-manuals/A2B-ADS-Goldhunter.pdf

 

[Sven]

Back in the day, you always kept hitting the retune button or adjusting the threshold if the tuning "drifts".
I remember with the Garrett Master Hunter and ADS version in all metal VLF mode, when we went hunting just around sun-up and it was cool,
tuning would stay constant but, as the sun came out and the air warmed, the detector's tuning would drift to a higher meter and threshold sound.
We just chalked this up to temp. difference. If the temp. was stable, drifting was not a big problem, if at all. You would still have to press the re-tune button now and then
as ground minerals changed.

Back to your detector, many out there still look in pristine condition. But, because they have been sitting around for sumteen years, they may not function properly.
First off I spray DeOxit 5 cleaner into the control pots and let them sit for a day. This fixes many a detector.
If the detector still does not work properly, many times its just capacitors drying out. They need to be replaced. Sometimes putting new batteries in and leaving the detector on for several days helps.
https://www.nmr.mgh.harvard.edu/~reese/electrolytics/

It is also a known fact, many of the older Garrett's coils go bad. Generally you can find replacement coils on ebay cheap. You may have to buy several coils to get the best performing one.
Garrett can fix many of the older detectors, the electronic component parts are common, should not be a problem. They may have many other parts, except for coil.

Below is a picture of a 1986 GroundHog 5khz Gold Hunter, the 15khz Groundhog air tests should be similar, if not you have a problem.

 

[Gene]

Very good point Fishers Ghost and absolutely correct.

 

[Gene]

Excellent information Sven. Thanks for sharing.