Tweet
I measure voltage with my multimeter about 12 V AC.I will go to my frend wich has an oscilloscope and try to adjust everything there.I haven`t 0,28 .I have 0,315 and I will wind 101/106 Tx/Rx .It gives more than 19 ohms .I think it will be fine for DD 27sm.
-
-
I found it.
The printed page that I used to mount is black-white.And I acidently mounted 20K insteed 220K because one 2 cant be seen under one line.Now sens is good.Even with coil for other device.
Wow I desolder and test almost all components.So now there are BC547 and BC557 for TX part.Device is quiet and stable.
Will make new picktures.At all points.Comment
-
Mystery solved, good work!Originally posted by Ultimate_Haze View PostI found it.
The printed page that I used to mount is black-white.And I acidently mounted 20K insteed 220K because one 2 cant be seen under one line.Now sens is good.Even with coil for other device.
Wow I desolder and test almost all components.So now there are BC547 and BC557 for TX part.Device is quiet and stable.
Will make new picktures.At all points.
-SBComment
-
Hi,Originally posted by Ultimate_Haze View PostI found it.
The printed page that I used to mount is black-white.And I acidently mounted 20K insteed 220K because one 2 cant be seen under one line.Now sens is good.Even with coil for other device.
Wow I desolder and test almost all components.So now there are BC547 and BC557 for TX part.Device is quiet and stable.
Will make new picktures.At all points.
clean that PCB, soldering flux you have to clean. Not always is a problem but sometimes IS, so better clean.
Use cotton + isopropanol (isopropil alcool), can find in stores... used for dissolving stains on clothes... instant stain removers...
Can use other stuff too... also acetone if have it, tin joints become gray and not shiny but acetone dissolves ANY flux easy and without brushing much with cotton.
In extreme cases can use a tooth-brush and acetone (work outside , do not inhale vapours) , drop acetone and use plastic brush , anything will dissolve in no time, then refine with e.g. cotton or paper towel full of new acetone.
Isopropanol is much better, anyway, clean without affecting e.g. shiny tin joints and it's less aggressive against copper than acetone (uncovered with enamel copper will develop stains later and corrode more easy, but take months or years)
Can also use ethanol too... but be sure it's pure and very hi grade, use cotton and the like.
Generally avoid paint solvents... cause are a mix of stuff and can damage solder side and create paths for currents.
Kind regards,
MaxComment
-
Hi ,
One question about the TSG ( first initial version) :
I have doubts about the cap's ( all ceramic) I've used on my pcb cause of the low sensitivity: Is there a significant difference when there are other cap's used ? ( I don't know for shure which type should be used)
thnx in advance
DannyComment
-
Dennis, what is so hard about finding good quality capacitors?
You should use polyester or Mylar film caps for most. Polycarbonate is also good or maybe better but hard to find.
Use Polystyrene or polypropylene for the transmit tank and also the receive tank. These are desirable because you want low loss and temperature stability. Polyseter is mediocre but much better than any ceramic cap you'll likely find that's big enough to work here.
Ceramic capacitors might be OK in some places but you had better understand the differences and select wisely between Z5U, Y5V, X5R, and COG/NPO if you want decent performance. You also need to understand voltage derating before you employ ceramic caps, even more so than for film types.
Ceramics can be used some places, but not a good idea unless know the cap's specs and choose wisely after some research.Comment
-
It is unlikely that the low sensitivity is caused by using ceramic capacitors throughout the design. Polyester caps would be preferred in the TX and RX circuits, but not essential. Ceramic caps are best for coupling, decoupling and filtering. If you change the TX and RX caps for polyester types, I doubt you will notice any difference.Originally posted by Dennis the Mennis View Post
Please define what you mean by "low sensitivity". Presumably you are referring to detection distance?Comment
-
check your coilOriginally posted by Dennis the Mennis View Post
if needed do another
Kind regards,
MaxComment
-
TGS PROB
i constructed this version... but i have one problem... i nulled the coil, when i connect the coil in pcb i hear only a continues sound with no other responce....!!!!
This schematic has mistakes??. I check the polarity of RX but nothing.... the sound is the same always!! When i disconnect the coils only this time stop...
thanks GeorgeComment
-
George don't worry, schematic and pcb are ok. You don't have negative voltage on your detector - that's why you get continous audio.
You should read this thread from a beginning and find answers to your problem. It is easy problem, 5 minutes to fix!
Regards!
Comment
-
Hello,George!I had the same problem first.It turned out IC 4024.I replaced it ,and everything is okay about sound.I have a quiestion to experts.When I null with scope at pin 7(Lf353) ,and then measure the same pin with multimeter I read about -180mV.There is some sensitivity -1euro about 10sm.When I null at pin 7 with multimeter -it shows 5-10mV -the scope shows that is not nulled at all.I tried with two different pcb-s -1265 and the last one for the schematic above.Can this be a coil problem,or something else?Pin 1 of LF353 has broken graphic too.I turn this broken graphic into a nice sinusoide by placing 100pf paralel with 100k rezistor (Lf353)The same effect may get by replacing 2,2k (emiter 2N2907) with 4,7k.But the main problem is coil nulling -the meter and scope show different place of nulling coils.Comment
-
thanks ivconic.. i will check the negative voltage ( 0V you mean)
thanks Pompey after checking voltage i will replace 4024!!Comment
-
Voltages are 7,9V and -6,13V to me. You must get -6.xx for negative voltage when you atach Tx coil.Originally posted by GeorgeGW View PostComment
-
7,9V in schematic at TX J1 pin and -6.xx J1 pin 2, right?
Comment
-
You have +8v and gnd from 7808. Minus voltage is generated in stage after 4024. It should be approx. -6.20V +/- 0.15V.
Situation is already explained. But let me repeat:
TX transistor 2N2907 with LC tank forms oscilator and run at approx. 14kHz (if TX coil is 6mH). Signal is fed to buffer transistor 2N2222 base through 100K resistor. Than from it's collector, through 1K resistor to pin 1. of 4024. 4024 is divider and divides main 14kHz. On pin 12. there is 1/2 of main frequency, 14kHz/2= 7kHz. So 7kHz signal is further fed through 2 x 4K7 resistors to chopper transistors bases. Those 2 chopper transistors in conjuction with 2 x 4148 diodes and 2 x 220uF capacitors are forming "negative voltage generation stage" with approx. -6.xx volts at output.
...
So...if you get continous audio it means (in 99% of cases) that you don't have proper negative voltage. Reason could be buffer transistor 2N2222 or 4024 or those 2 chopper transistors. In most of the cases all the mentioned components are supposed to be alright. Problem lays in signal level in mentioned paths. Signal is not strong enough to "open" transistors bases. Somewhere from collector of TX 2N2907 to chopper bases signal is somehow attenuated. To void to much of phylosophy simply you can replace those 2 chopper transistors and put two of different kind (BC107&BC177, BC557&BC547....). Or to replace 4024 from one manufacturer and put one from other manufacturer. At the end you can try to replace buffer 2N2222 with BC547 or simillar. It will start to work properly for sure. Signal is a bit attenuated - not much. It will need a minor amplification to reach level enough to "open" bases at chopper transistors.
Pretty common source of that attenuation can be 4024. It acts like divider there. Logicaly in process of dividing it attenuates origin signal at some percentage.
....
Comment
Comment