Vintage Garrett metal detector pot replacement

[khandasaif]

Hi,
I need to replace 2 pots on an old Garrett groundhog detector. The originals have no values marked on it and the tracks (carbon ) in both are badly worn so cannot measure the resistance. The only markings are numbers, probably manufacturers marks......same on both

-1377702 93013

Does anyone know what the values could be, thanks

David

[homefire]

What detector is it. They had more then a few going by GroundHog.

[Overtheedge]

On many pots, you can pull the metal cover off and get access to the carbon track.
The wiper usually doesn't completely cover the carbon track and there will still be a continuous arc to measure.
Length of arc is resistance while width of track is power handling capacity.

eric

[khandasaif]

Thank you for the replies.

The MD is a Garratt Coin hunter

Hi Eric,
Both pots have been taken apart, both tracks have areas which are completely wiped. Perhaps a previous owner had over cleaned or even sanded the carbon track ( I' ve only just bought it).
Would measurement of the length and width give me the Ohm value I need ?

Thanks for your help

David

[homefire]

Look for numbers on the side of the Pot. 503?

[khandasaif]

Look for numbers on the side of the Pot. 503?

Thanks for the reply. No, only the numbers stated.

I took the pot apart again and using an ohm meter measured the resistance for the best remaining section of carbon. I measured approx. 153 K along a section which would be approx. a 1/4 turn .......on that basis would a 500k linear pot be an ideal replacement ? (I know that 4 x 153 is nearer 600K but assume that the damage to the track may affect the result a little)

[Altra]

On an old paper schematic I have (ADS 4 Ground Hog).

Sensitivity - 25k
Threshold - 250K
Ground Bal - 25k 10 turn
Disc 250K

There are schematics here on the forum

Did a quick search
http://www.geotech1.com/forums/showt...ght=ground+hog

[khandasaif]

On an old paper schematic I have (ADS 4 Ground Hog).

Sensitivity - 25k
Threshold - 250K
Ground Bal - 25k 10 turn
Disc 250K

There are schematics here on the forum

Did a quick search
http://www.geotech1.com/forums/showt...ght=ground+hog

Thanks for the heads up on the schematics. I do have 2 other Groundhogs ....a A2B Gold Hunter and a coin hunter , but, are unavailable at the moment. When I can get to them, I'll open them up and measure the pots......I've modified both a little, if there's any interest I'll also put some pics up . Thanks again.

David

[SVEN1]

Garrett still had the pots last time I contacted them for replacements.
You can use any pot brand you like as replacements

[khandasaif]

Garrett still had the pots last time I contacted them for replacements.
You can use any pot brand you like as replacements

Sven,
do you have the contact details for Garratt replacement parts. I'm in the UK and assume that the only source of vintage parts would be the US ?

I think I may have found the reason that the pots have had their tracks 'over cleaned'. On the PCB where the pot is connected is a resistor, colour coded for 2 M Ohms but measured 1 M Ohms. Perhaps the reduced resistance prevented proper adjustment via the pot and a previous owner tried to repair that, rather than check the circuit

Regards David

[SVEN1]

Try Brad at Garrett USA [email protected]