TGSL-VLF ///just ask!

[galal]

sry large size images,this maybe better

[galal]

i forgot to till you that in the photo n3 for TX wave was measured at J1-1 but the wave for RX was measured at J2-1 also not pin7 101

[Jerry]

Hi guys
sorry for delay,i have been looking about an oscilloscope when i get one i have measured the frequency,but before this i forgot something that i have checked the pcb it's don't have any short and the resistors R9,R10 is 4.3K not 4.7k damn the seller,and with respect to the frequency this is the result:

1) pin1 4024 equal 14.7khz

2) pin12 4024 equal 7.14khz

3) TX and RX freq and the phase shift between them

Don't worry about 4.3 vs 4.7K for R9, R10. Not far enough off to be causing that large of a drop in the minus supply voltage. The pictures show that you do have a lot that is working OK. The phase shift between tx/rx is off but that is not your problem for the moment. We still need to know what the voltage is on the minus supply when everything else has been disconnected downstream from C5/D6 junction point.

Have you taken any resistance measurements on the minus supply with the power turned off? Resistance should read several thousands of ohms and show charging a cap. (C5)

Getting your detector up an running is a whole series of small steps and debugging is no different. The answer is there, we just dont know what it is yet.

Jerry

BTW: That scope is going to really come in handy.

[galal]

i have disconnect everything connected at -5v except ICs, i see that only R43 connect to -5v Right? but the voltage still -3v

note:when i measured voltage at pin 12 4024 it's was 8v without the coil and when i connected the coil it's become 3v; could this be the problem?

[Jerry]

i have disconnect everything connected at -5v except ICs, i see that only R43 connect to -5v Right? but the voltage still -3v

note:when i measured voltage at pin 12 4024 it's was 8v without the coil and when i connected the coil it's become 3v; could this be the problem?

Last thing first. Pin 12 of the 4024 puts out a square wave to drive the switching transistors, TR7 & TR8. Each time the voltage at pin 12 changes from 0 to 8 or 8 to 0, one of the switching transistors turns on and the other turns off. Without the coil connected, one of the switching transistors will always be turned on and the other always off and no AC voltage will be generated for the diodes rectify into minus voltage. However with the coil connected, pin 12 alternates between 0 and 8 volts so your volt meter is seeing an average of the pulsing DC signal so it is reading lower. That isnt you problem.

Now to you first point. What I have been trying to convey is splitting the minus power supply circuit right at the power supply. That is the simplest way to find out if the problem is associated with the part that actually generate the minus voltage or elsewhere.

If you have not unplugged the IC's, I recommend that you do and then see what you get. You should be seeing about -6 volts on pin 4 of each IC including the LM308's. If your IC's are soldered to the board then I would suggest breaking the circuit right at D6 & C5. Once the minus power supply is isolated from the rest of the circuit and you are still getting only -3 volts then there is no need to look anywhere except for the few components between pin 12 of the 4024 and D6/C5 junction.

Jerry

[galal]

pls take a look on the photo ,also those points should be separate from minus supply?

[Jerry]

pls take a look on the photo ,also those points should be separate from minus supply?

The points you have indicated are all ground and are (or should be) separate from the minus supply. The minus supply is measured in reference to them. If you have everything disconnected and are still getting -3v, then the problem is within the area you have circled in green but to the right of the 4024.

Have you checked to see if anything is warm to the touch? Also, how much current does the circuit pull with everything disconnected?

Another thing, can you take some good close up pictures of top and bottom of the circuit board? Maybe more eyes looking at it will find something.

Jerry

[satdaveuk]

Maybe worth checking your meter for accuracy, I only say that because something doesnt ring true here, just a thought because we have all been caught out in the past.

Regards

[galal]

but i have also measured it in the oscilloscope reading was -3.6v almost the same, and jerry i have disconnected everything related or connect to minus battery and D6/C5 junction except ICs,but when I did this and i measured the voltage between D6/C5 junction and minus battery; it's didn't give any volt not -3 or -6v nothing it's like when i disconnected the coil,are you sure about this that should disconnect everything about minus supply

[Jerry]

i have disconnected everything related or connect to minus battery and D6/C5 junction except ICs,but when I did this and i measured the voltage between D6/C5 junction and minus battery; it's didn't give any volt not -3 or -6v nothing it's like when i disconnected the coil,are you sure about this that should disconnect everything about minus supply

Which Ic's are we talking about? You need the 4024 for the minus supply to work but the rest need to go away so we can test. In other words, everything not within your green circled area. On a new circuit board, everything is suspect at this point and nothing is good until you can verify that it is good. It amazing what can and will happen during the process of populating a circuit board with parts. So we need to start with smaller chunks of the circuit and prove that they work and then add in things until the problem appears again.

It may be instructive to just breadboard the oscillator and power circuit that you have circled in green and use it as a model for testing your TGSL board.

As I said in my last post, some pictures of your circuit board may help us understand what is going on here.

Jerry

[ashefr10]

the tgsl a friend is sensitive to his hand, when in fact it's hand approaches the electronic card the detector beeps as if there were interference

[galal]

jerry before everything, do you know something,but pls don't be angry,really i didn't notice that,i talking about TR7,TR8 i have invert the pins not connected them like in the schematic, and the same thing with TR1,TR6 look on the photo and you will know what i mean,how can that affect?could this be the problem?

[Jerry]

jerry before everything, do you know something,but pls don't be angry,really i didn't notice that,i talking about TR7,TR8 i have invert the pins not connected them like in the schematic, and the same thing with TR1,TR6 look on the photo and you will know what i mean,how can that affect?could this be the problem?

I am not angry but I am trying to understand what is going on. Sorry if gave that impression. The schematic is correct and that is the way the transistors should be orientated. I would say that the way you have TR7, TR8 shown could be the problem...... Except that the scope pictures you put up a while ago show pretty normal oscillator wave form. That should not be if the transistor is hooked up wrong, so now I am getting confused. Are you really sure of the identification of the collector and emitter leads on all of the transistors? Would not hurt to double check everything including the 220uf caps for proper orientation.

Putting parts in wrong is really easy to do. I speak from experience

I think we are getting closer to the root of the minus supply problem. I think you still have others, but they can wait until this one is figured out.

Jerry

[galal]

seems that i will give up,but i can't because my relatives want me to finish it and i really want to make it,look whats happen now;i have fixed transistors that connected wrong, and i have reset minus supply as it was, everything now is like the previous,and i connected the coil,but now there's no minus volt on D6/C5 nothing,and also there's no volt on pin12 4024 it's very small,what is basically make volt and make no volt on pin12,in the previous it's was -3v now it's become positive very very small volt,exactly like when the coil is disconnected,so what is caused that?

[Jerry]

seems that i will give up,but i can't because my relatives want me to finish it and i really want to make it,look whats happen now;i have fixed transistors that connected wrong, and i have reset minus supply as it was, everything now is like the previous,and i connected the coil,but now there's no minus volt on D6/C5 nothing,and also there's no volt on pin12 4024 it's very small,what is basically make volt and make no volt on pin12,in the previous it's was -3v now it's become positive very very small volt,exactly like when the coil is disconnected,so what is caused that?

Are you very sure about the lead identification on the transistors? At one point you had a working oscillator. Lets go back and start with that. and,

1. Make sure you have a signal from the oscillator.
2. Make sure that this signal is passing through TR6 to pin 1 of the 4024.
3. Check for a square wave output at pin 12 of the 4024. It should be a pulsating DC square wave of lower frequency than on pin 1.
4. Check the signal at the junction of the collectors for TR7 and TR8, it should be a pulsating DC square wave.
5. Check the polarity of C4, the + side should be connected to the collectors of TR7 & TR8.
6. Check the polarity of C5, the + side should be connected to ground.
7. Finally check for minus voltage at D6 & C5.

When you get all of those conditions and nothing is connected to the minus supply, you should get about -6 volts DC or thereabouts.

I know it can be frustrating trying to find a problem, and it is sometime helpful to set it aside for a few days and come back with a fresh outlook.

Meanwhile, it would be helpful if you could take some good close up pictures.

Jerry