2 questions about R14 & U7

[jokefia]

Hello Every one,

1) I have replaced LF412A by using LF353P TEXAS INSTRUMENTS , voltage for U7 (pin 1) was -3.21V but now is Zero, voltage for (pin2 and 3 ) is Zero too, pin 4 is -4.98V , ( pin 5 and 6 ) are Zero, (pin 7 ) 3.52V, (pin 8 ) is 4.92V

2) I have short pin2 of PL2 to pin 1 and set the DC voltage level with voltmeter to -2.1V (((USING R14 Pin show in attached photo!))), when i UN-short pin 2 & pin 1, the voltage return to -2.93V

would like to get comments about this issue

[kt315]

hi
i am not so strong in 'geotech' version board. also, reference designators of the pcb is not matched original PCB/schematic.
thats why hard for me to answer if people use non-original RD.

1/ no difference what you use, lf412 or lf353.
2/ you can not measure impulse signal by ordinary tester. he measures - either just clear sinusoidal signal (what we call - AC)
or potencial level (DC) ("clear flat").

[Qiaozhi]

Hello Every one,

1) I have replaced LF412A by using LF353P TEXAS INSTRUMENTS , voltage for U7 (pin 1) was -3.21V but now is Zero, voltage for (pin2 and 3 ) is Zero too, pin 4 is -4.98V , ( pin 5 and 6 ) are Zero, (pin 7 ) 3.52V, (pin 8 ) is 4.92V

2) I have short pin2 of PL2 to pin 1 and set the DC voltage level with voltmeter to -2.1V (((USING R14 Pin show in attached photo!))), when i UN-short pin 2 & pin 1, the voltage return to -2.93V

would like to get comments about this issue

Did you follow the instructions in the Build Document where it says:

'If you go through the following steps carefully, and in order, you will have a greater chance of
ending up with a detector that actually works. Please do not proceed to the next step until you have
solved any problems encountered in the current step. If you get stuck at any stage during the build,
then seek help in the Geotech forums before moving on. Do not simply populate the whole board;
discover it doesn't work (which will be the most likely result) and then post in the forums: “I've
built the Geotech Baracuda, and it's not working. What's wrong?” .... as you will receive little
sympathy from other Geotech members.'
?????

[jokefia]

YES Qiaozhi i'm in step 7 now and i will stay there until things solved, " voltage for U7 (pin 1) was -3.21V but now is Zero" is it possible that some component are damaged??

[jokefia]

kt315 ... thank you