DIY TGSL STEP BY STEP BUILDING AND TESTING

[Nandor]

Those are 100nF capacitors on the voltage rails of the LM308 Op-amp for filtering. They can be 150nf, 220nf or any other it's not critical. The PCB traces are long that's why you need capacitors on every Op-amps rail pins.

[Hyena]

Those are 100nF capacitors on the voltage rails of the LM308 Op-amp for filtering. They can be 150nf, 220nf or any other it's not critical. The PCB traces are long that's why you need capacitors on every Op-amps rail pins.

Typo: it should be 100pF

[chuubaba]

Populated my second TGSL board today. Connected everything with it except coil but it is silent. Power is 13V DC.

PROBLEM !
The voltage on pin 4 of lm358 is 0.36V instead of -5V. How i correct this. My c3 and c28 is 220uf 35V.

[Hyena]

Populated my second TGSL board today. Connected everything with it except coil but it is silent. Power is 13V DC.

PROBLEM !
The voltage on pin 4 of lm358 is 0.36V instead of -5V. How i correct this. My c3 and c28 is 220uf 35V.
[ATTACH]43665[/ATTACH]

NEVER run tgsl without coil!!!

Connect Tx coil and check negative rail again

[chuubaba]

Fixed. Thank you for quick remedy. Why it is silent when every component and joint i fixed is more than perfect??

NEVER run tgsl without coil!!!

Connect Tx coil and check negative rail again

[chuubaba]

I have soldered 100nf ceramic already. How serious is it if a fault?

Typo: it should be 100pF

[Hyena]

Fixed. Thank you for quick remedy. Why it is silent when every component and joint i fixed is more than perfect??

I guess its because your fix is far from perfect Dont know.
Change caps to 100pF and send photos of your PCB both sides in high resolution. Also coil... Then we can use our witch crystal ball more preciousely

[rickb]

chuubaba
\
The tx coil is part of the oscillator! Hook it up!
The rx coil is part of the receiver! Hook it up!
You say you haven't made the DD coil set? Do it now!
How many times does the above have to be said?
\
Do you know how to trace a signal step by step through a schematic?
Use your scope to diagnose problems, not your ears.
\
I'm not convinced you're not a troll.
Just buy a detector.

[kt315]

Fixed. Thank you for quick remedy. Why it is silent when every component and joint i fixed is more than perfect??

look on schematic. no TX coil - no generation. no generation - no negative voltage.
if you choiced schematic you must see all problems.

[dbanner]

chuubaba
\
The tx coil is part of the oscillator! Hook it up!
The rx coil is part of the receiver! Hook it up!
You say you haven't made the DD coil set? Do it now!
How many times does the above have to be said?
\
Do you know how to trace a signal step by step through a schematic?
Use your scope to diagnose problems, not your ears.
\
I'm not convinced you're not a troll.
Just buy a detector.

Chu, you must allay the troll talk by putting picture of your NEW pcb. Do not let such an allegation stand against you or people will begin to have doubts.
You used method of chemical transfer of print onto copper board, yes? Can you say how your experience was with this method.

[dbanner]

I have soldered 100nf ceramic already. How serious is it if a fault?

This is not prevent detector from working, you can change them whenever, maybe go ahead and change them, but is not the reason your circuit is not working.
You have to make a list of steps to go through. you can find everything in the Build document. Do you have the Build document?
If you do not put pics of your new pcb BACK AND FRONT, it is unlikely that anyone would been keen on assisting.

[chuubaba]

My TGSL is based on apberg's single side version. I am now using c3, c28 as 220uf 25v instead of 220uf 35v. After i attached a makeshift coil it is giving a beep if i attach any pot wire or oscilloscope probes. Mostly it is beeping very faint. I can see the Tx wave change with hovering of metal objects or movement of Tx coil (time/div knob set at 20uS; Volt per div knob at 1V. The voltage on Tx coil are 7.35v; same knob position as Tx. There are some milliVolts on Rx. The voltage on pin 4 of lm358 is -6.42v. Ground balance pot makes sound on connection and works towards one end of the the pot turn. The discrimination switch, sensitivity, discrimination pots sound on connection but nothing translates on scope.

[dbanner]

Now that's what I'm talking about! Great job Chu! You did work very hard In short time to redo the whole thing.
If you have beep, then the circuit is good.
The only thing left is to put proper coil and tune everything.
But before you do this, here are a few things to know in general.

[chuubaba]

Is this the build document ?

........... Do you have the Build document?.....................................

[dbanner]

Firstly, capacitors are having a voltage rating. All this means is that you must use at least the minimum that is recommended for the caps on the part/components list. You can go higher, but not lower. So if parts list says 220uf@25V, you can put 220uf@25V and above. So 220uf@35V is also good. Anything above 25volts, but not below. Got it?