TGSL Tuning & troubleshooting

[ripsdevala]

I think u can use 2n2906 or bc327, or u can find it 1 or 2 in junk pc board labeled 2F or W2F, its sot23 package, u need to create the legs

[Nandor]

Those are general purpose pnp and npn transistors there are many replacements. The important thing is to match them with the same hFE value.

[BKY1337]

What about C558B or BC558?

[BKY1337]

I tried the BC558 right now and i have -6.3V at the pin 4s. I have also about 20cm depht with a euro. Its very noisy , chattering.

I still have not the 10 volts at the tx coil. Only a few mV. I think something else got damaged too.

I have ordered new 2N2907. I think i should wait until my DSO has arrived.

[Nandor]

-6.3 volts is good, that means that the oscillator works! Tx voltage should be 14~16 volts. Don't know what to say you should upload some nice quality photos so we can see your pcb and coil. It would be easier to find the problem.

[BKY1337]

Why? The coil is already potted and the pcb is a standard silverdog TGSL EDU board. Every component is where it belongs to.
I know that because it worked before i had the short connection. I can upload the picture from the oscilloscope when it has arrived.

[Nandor]

I just tried to help you. Something is wrong with your pcb that you can see thats why!

[BKY1337]

I tried it again and i think the clackering is because at my testcoil the coils are swapped. Thats why i made a new coil.
I try to solder the GX 16 connector to the board at the moment.
But i cant remember which tx hole is for what. Can you help me?

Is the upper TX hole number 1? And the lower 2?

What about the RX holes? Left 1 and right 2?

[dbanner]

First of all, good to see you got it working somewhat. There is no way you could get 20cm depth with just a few milivolts on the TX coil. What if you are measuring wrong coil? Otherwise your meter is at fault, all things being equal. You can't remember which hole is for what? Come'on, This is rank intellectual laziness. There are documents for tgsl build using silverdog's layout here on forum. You can figure it out if you take the time to read through carefully, step by step.

[ripsdevala]

U know, im not get 16v on Tx using my DMM, but will show on scope, vpp not dc or maybe i miss reading. For now i got the standart geotech deep at 30cm air test from medium brass coin in high emi interference, i hope will be ok on the field.

[waltr]

First of all, good to see you got it working somewhat. There is no way you could get 20cm depth with just a few milivolts on the TX coil. What if you are measuring wrong coil? Otherwise your meter is at fault, all things being equal.

A possibility of why his DVM is measuring a low Voltage is the DVM's bandwidth. Most DVM's do time averaging and do not respond well to frequencies higher than AC Mains (50/60Hz) even on AC Voltage scale.

[dbanner]

Yes, My cheap DMM only measured about 4V on Ac range. I think it depends on frequency response(bandwidth) of DMM. My good DMM was stolen from shop. So now I use cheap chinese made. Does the job at 50/60Hz but 14000Hz? No Way.

[BKY1337]

It worked before , so i think i should be able to measure the 11 Volts like before. I tried to connect my new coil and tried to null him, but i can only reach 20 cm with a euro and only a weak signal. My Coils are properly made with graphite shielding because i try to reach 40cm depth.

I cannot find the Numbers of the TX and RX holes. Not in the PDF fron Don Bowers and not somewhere else.
I found Notes which i made while i was building the old coil.

They say: TX left -> End
TX right -> Start
Rx above-> Start
Rx below -> End

But im not sure now. I can remember that i had the same problem with my old coils. Then i swapped the rx with the tx coil and the coil worked. But this is not good . Because Rx is 6mH at the old coil and Tx is 6,5mH.

The shield is not connected yet


Maybe the connections are wrong.

[dbanner]

Look at the schematic for clues, one side of Tx coil is grounded. This would be where shield connects. Now look for appropriate hole on pcb. AS for RX, the start/finish, well just flip the coil if you are getting the double beep thing, then this would correspond to start/ finish. If you didn't mark which wire was the start when you were winding coils, then it's not a problem.

[dbanner]

I learned some DMM's measure average RMS(root mean square), good only for smooth sine wave, while others measure True RMS, good for all kinds, but again bandwidth of meter is important. I learned most cheap DMM's have bandwidth of between 50-500Hz. Not good enough to measure coil voltage. You need a meter that measures at least average RMS at a bandwidth of at least 20KHZ.For a cyclically alternating electric current, RMS is equal to the value of the D.C that would produce the same average power dissipation in a resistive load. In order to measure peak to peak voltage, you would have to multiply the RMS reading on meter by a factor of approx. 2.8(for true sine wave)