HELP TWO POT ON PCB GARRETT GTA 500 WHAT THEY USED PLEASE

[ashefr10]

Hello ,Hello, I was given an old garrett gta 500, I notice two pot on the bottom pcb, apparently one is the ground ballancing against the other I do not know what it is, can you tell me say if you know what it is. thank you

[Altra]

They are for ground balance and disc calibrate. They go to a LM393 comparator which controls the phase of the demodulators

Almost all the coin detectors use this scheme.

[ashefr10]

OK thank you, I set it in the ground effect quite easily but the other how do I go about to set?

[Altra]

The other you would adjust by watching the LCD. A 1oz silver coin would indicate to the far right icon. Aluminum foil would read under
that icon. Iron would read to the far left icon.

[ashefr10]

ok, thank you for these explanations to this setting should I put in A or B?

[Altra]

I have no idea what A and B are? Its been about 15 years since I held a GTA500. I would use A since that is probably "normal"?