Part 1: the board and how it's connected

I'm looking at a headphone sound amplifier that is used to help experts detect pests in palm trees when a microphone is placed on the trunk of the palm tree. Here's what the board looks like on the front,

Not a surprise, IC sanded on purpose

On the left side are 9V battery wires coming in to supply the whole circuit . Top right is ( i presume ) microphone pre-amplifier circuit which has input from a microphone ( silver Wire is the Signal Line while the bare wire is ground ) , the output of the BJT microphone circuit (brown wire) gets through a potentiometer to the input of the unknown IC (red wire) , the IC is then connected to the purple and blue wires which go to the headphone . The yellow and green are 9V Lines that are connected / disconnected through a switch .

Part 2: my conclusions for far

Here's my guess,

  • The BJT circuit is a microphone preamplifier circuit .
  • The IC is some sort of a special purpose Audio-ish amplifier .

Part 3: schematic of the board

Schematic traced from the PCB

Part 4: my questions

  1. What is the IC Model/Type/Category .

  2. BJT Circuit drawn earlier ( Preamplfier ? ) .

  • \$\begingroup\$ The IC marking is unreadable in that photo. Try under a microscope or magnifier with light from an angle. \$\endgroup\$
    – pjc50
    Commented May 23, 2016 at 15:56
  • \$\begingroup\$ This is a nice question with a lot of details. I can't answer, but I want to comment about the potentiometer. Usually it has three connections, you have only drawn two. \$\endgroup\$
    – pipe
    Commented May 23, 2016 at 15:56
  • \$\begingroup\$ @pjc50 It looks like the marking has been scraped off, either accidentally or on purpose.. \$\endgroup\$
    – pipe
    Commented May 23, 2016 at 15:57
  • \$\begingroup\$ 1. IC Marking is sanded off \$\endgroup\$ Commented May 23, 2016 at 16:49
  • \$\begingroup\$ 2. Potentiometer / Switch Hybrid has the following wires : A. Yellow : 9V from battery , B. Green : 9V at the load side ( Circuit ) , C. Orange : Ground , D. Brown : Microphone BJT Circuit Output , E. Red : Potentiometer Output \$\endgroup\$ Commented May 23, 2016 at 16:50

1 Answer 1


Can't be absolutely certain but the IC looks to be a TDA7052 (http://www.nxp.com/documents/data_sheet/TDA7052.pdf)

enter image description here

The bjt looks like a pre-amp stage for an electret microphone. Not totally convinced you have the correct circuit but there are lots of similar circuits out there on the net you could use.

for example:

enter image description here


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