made 2 tgsl both same problem. no sound.

[sukri01]

Anyone can tell me why both tgsl i built following qiozhi's complete detail dont make any sound at all?
is there any changes on the pcb i should know?
please help me.. ive made several circuits from geotech but i only succeed in making surf pi. please some help..s

[sukri01]

Special thanks to sven1's tip . my TGSL is making progress. There's audible tone now. I have made coil with 6mh and Rx 6.5mh but not shielded yet.
but result is very poor , i can only detect a 2 cm coin at 5 cm distance

[sukri01]

i found out 2n2222 and 2907 was in reverse . I am not sure if anything else is in reverse. bf 247 is it ok?

[sukri01]

tx and rx output v/div set at 2v t/v 20us

[sukri01]

does anyone have any idea why i got so poor detection?

[Silver Dollar]

Mine was only getting 6" until I discovered I put 470pf caps where 470N were called for (at c18 and c21).

I built this circuit and injected a 20 mv signal and watched (on the scope) the signal grow until it disappeared after those caps.

Use a .01 uf cap to decouple the output and set the pot so you have 20 mv signal and use it to trace out the circuit...

I found the 1 meg can be 50K and you want 4 - 10 hz with 7 hz the best to get through the filters.

[6666]

[ATTACH]26767[/ATTACH] i found out 2n2222 and 2907 was in reverse . I am not sure if anything else is in reverse. bf 247 is it ok?

Sukri01
would you mind telling me why the 2n2222 and 2907 were reversed, just trying to find out why that happened ?

[sukri01]

components placement and ic pin out are not same. i have to reverse the position then i got sound, and oscilation.

[6666]

Hi Sukri01, thanks for reply
thats a problem with TO-92 pinout,
I am tempted to write a simple tutorial about the problem

• There is no standard pinout for the TO-92. The American BJT's use the E-B-C pinout while their Japanese counterparts use the E-C-B pinout and some RF devices use the B-E-C pinout.

This quote is so true
More often than not, however, the disadvantages concerning accidental destruction are greatly outweighed by the small size and low cost of producing TO92 cases.

[Silver Dollar]

Yes those pinouts can get you. I found this drawing in one of the other threads around here;