Problem with Electronic Eavesdropping Devices Detector

[nanisyako]

rf bug detector

I made and put all of the components. but the loudspeaker is working when I put the battery and it doesnt detect anything how can I fix it. the project is take place in that link http://english.cxem.net/guard/guard28.php please help

 

[karesz]

rf bug detector

Hi,
If you can nothing change with the threshold potentiometer_I think you have to check all components for miss position/values or solder failures as shorts/non contacted...
Otherwise is Audioguru active on EDAboard too ...
K.

 

[nanisyako]

Re: rf bug detector

Hi,
If you can notihng change with the threshold potentiometer_I think you have to check all component for miss position/values or solder failures...
Otherwise is Audioguru active on EDAboard too ...
K.

yes he is corrected but absolutely it is not working. I get help to solder it from an expert soldering I made it two times and two times ithe loudspeaker is make voice without signal when I put the battery it starts to work. I will fail if has not working till next week:S

 

[karesz]

rf bug detector

I think, it has some component failure/miss populating or even solder failure...
You must not fall in panic_I can understand it, but it make sno progress fo you_, tell simple what does i.e. the potentiometer, has it some influence on your "loudspeaker effect"?
You must go on & measure the DC voltages on all points from both transistors Base & collector D1 Cathode, P1-R12 In the middle & in both extrems rotated, A1-pin1,A2-pin14,A4-pin8 & R11-R13 (all referenced toGND/negative of battery)...
@poor mystic,
its a simpler AM detector, but if it has (eventually)problems as a DC part...
K.

 

[poor mystic]

Re: rf bug detector

Hi Nanisyako
I guess you have no test equipment? Then it is time to bring out the "wet finger" methods.

If you have electrical mains wiring nearby as you test the circuit, your body will have a small voltage on it that you can introduce into the circuit. To follow this suggestion, you must very carefully touch the circuit at "high impedance" points and listen for a hum in the loudspeaker.
Use a probe of some kind to get the signal from your body into the circuit. I suggest you start by touching pin 10 of A4, and if you get a satisfactory hum in the loudspeaker go back step by step through the circuit, next testing pin 14 of A2 and continuing back until you find the fault.

Please let us know how you are going!
M

 

[nanisyako]

Re: rf bug detector

I think, it has some component failure/miss populating or even solder failure...
You must not fall in panic_I can understand it, but it make sno progress fo you_, tell simple what does i.e. the potentiometer, has it some influence on your "loudspeaker effect"?
You must go on & measure the DC voltages on all points from both transistors Base & collector D1 Cathode, P1-R12 In the middle & in both extrems rotated, A1-pin1,A2-pin14,A4-pin8 & R11-R13 (all referenced toGND/negative of battery)...
@poor mystic,
its a simpler AM detector, but if it has (eventually)problems as a DC part...
K.

how can I fix the problem of dc?

 

[karesz]

rf bug detector

Hali,
As I wrote it above: measure pls the DC voltages minimum at the mentioned points, but check to that with the potentiometer in min. & maximum positions too....
You can try experimenting with it as "poor mystic" said, but it will not so easy...
K.

 

[nanisyako]

Re: rf bug detector

Hali,
As I wrote it above: measure pls the DC voltages minimum at the mentioned points, but check to that with the potentiometer in min. & maximum positions too....
You can try experimenting with it as "poor mystic" said, but it will not so easy...
K.

I measure all of the pins and resistor which u mentioned above and let me to share with u potantiameter:1.8
base of transistors:-2
d1 cathode:1.8
r12:1.8
pin1 4.7(when ı open the transmitter it is become 5.2)

pin14:2.9
pin8:3.3
r13:3.6
r11:3.6

 

[bucklj]

Re: rf bug detector

Hi nanisyako,

don't panic - you will have to work to solve problem but should be possible to work through circuit systematically.

This is not a very well designed circuit as does not look it wil be very sensitive - u will probably need a large RF power signal (e.g. mobile phone) to see if it is capable of detecting RF - I attached doc to help debug and first step is to do basic checks - then, see if amplifier+detection stage can detect a strong RF signal like cellular phone - if it does, then the audio section is probaby at fault (may be possible to test separately) and is next step to test.

All the best,

Bucklj

 

[nanisyako]

Re: rf bug detector

Hi nanisyako,

don't panic - you will have to work to solve problem but should be possible to work through circuit systematically.

This is not a very well designed circuit as does not look it wil be very sensitive - u will probably need a large RF power signal (e.g. mobile phone) to see if it is capable of detecting RF - I attached doc to help debug and first step is to do basic checks - then, see if amplifier+detection stage can detect a strong RF signal like cellular phone - if it does, then the audio section is probaby at fault (may be possible to test separately) and is next step to test.

All the best,

Bucklj

I controlled it and all of the pieces are in the correct place. I measure the current and it was 70mA how can I fixed it and yes u right its sensitivity so bad again how can I fix it. I try it with mobile phone it about 900 Mhz there was some changing in the loudspeaker but I doubt about the EM field affect the loudspeaker how can I be sure?

 

[karesz]

rf bug detector

Hi Nanisyako,
you said "the loudspeaker works" if batter yis connected_ what means it pls, what can you hear?
Som eproblem is with the DC measuring, thta maybe you have a pulse on the pins/points, but the equipment displays a middle value of them....
Is it installed with an IC socet; can you carfully pull/bend i.e. pin 1 out, that makes no contact to the socket metall?
Other problem is, that I will be in so 3 hours on the way for 2--2.5 days, & I have to prepare my documents too; I can not make much in the next 3 houers & 2 days_sorry!
I hope that other guys can make it, help you!
Can you change some capacitors pls?
Depending of sorte, mosten the blue small ceramics, are problemativ after soldering_you can not see much outside, but after more solder time/higher temp as needed it will be melt under the lack/color stuff and is no more properly contacted inside to the electrodes...
Its only with a new one to fix, but solder it fine_not too long & hot pls.
I mean concret the C3/5/6/7/8 & C9...
K.