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Hi,
I decided to build a tgsl using the documentation from the tgsl complete details thread. I made my own pcb and soldered all the components. I wound the two coils. They are not exactly up to spec but very close. When connected to the transmit circuit TX coil is running at 14,45 kHz and the RX connected to the transmit circuit is running at 13,94khz. However there is a problem. Even with only Tx connected the detector starts beeping like it is detecting exactly 13 sec after being switched on. This happens when the detector is switched to **** mode. In all metal mode it is not as predictable and it is kind of difficult to know when exactly it will start(usually when I pass metal very near the coils.). I am able to null the coils to 0,010 v AC (pin 7 on lf353). I was able to measure all IC supply voltages and they are all in spec. The -5v rail is actually -6,30v. I don't know if that is OK. I have build this detector with new components. Everything is in place. The only part I was not able to find was the 2n2907 transistor. They sold me a KSP 2n2907 which has a different pin configuration but I flipped it around and it works. I will appreciate any help I can get. I do not know why this thing is not working. And one more thing. I was probing with a small speaker and when I touched the grate of j107 (in **** mode) it reset that 13 seconds.
I decided to build a tgsl using the documentation from the tgsl complete details thread. I made my own pcb and soldered all the components. I wound the two coils. They are not exactly up to spec but very close. When connected to the transmit circuit TX coil is running at 14,45 kHz and the RX connected to the transmit circuit is running at 13,94khz. However there is a problem. Even with only Tx connected the detector starts beeping like it is detecting exactly 13 sec after being switched on. This happens when the detector is switched to **** mode. In all metal mode it is not as predictable and it is kind of difficult to know when exactly it will start(usually when I pass metal very near the coils.). I am able to null the coils to 0,010 v AC (pin 7 on lf353). I was able to measure all IC supply voltages and they are all in spec. The -5v rail is actually -6,30v. I don't know if that is OK. I have build this detector with new components. Everything is in place. The only part I was not able to find was the 2n2907 transistor. They sold me a KSP 2n2907 which has a different pin configuration but I flipped it around and it works. I will appreciate any help I can get. I do not know why this thing is not working. And one more thing. I was probing with a small speaker and when I touched the grate of j107 (in **** mode) it reset that 13 seconds.