555+741 IC TESTER


2B-555 + 741 IC TESTER


This project is very useful for electronic hobbyist,  because both 555 and 741 are used in most of the projects and projects are easily performed with good result.  Due to use of FND in this project it is easily assembled.


This project has been developed and tested O.K. in our TV Engineers Technical Lab.  The components and PCB used in the projects published in our books are available for sale at resonable price.

This project is a boon for electronic hobbyist.  Because 555 and 741 IC’s are mostly used by them.  It checks the quality and fitness of IC555 and 741 so these can be used in other projects without any doubt.  The working system of this project is very simple and output of the circuit can be conformed from FND display.  IC555 is used as astable multivibrator in the circuit and output is available of 2Hz.  A common anode 7segment FND display has also been used.  IC741 has been used in inverting mode, Digit no. 7 & 5 are shown alternately in the FND display.  Testing of IC is done like this.  First time use new IC’s 741 and 555 and observe the display, Change the switch S2 in inverting mode.  IC 555 will show digits 7 and 5 and IC 741 will show the digits 9 & 7.   In case after taking out IC741 from its socket, display shows 5 & 7.  It means that IC555 is OK. If there is no display it means that IC 741 is faulty. If both IC’s are faulty or in non-operating state then display will indicate the digits 7 [Switch 2 may be in any position].  If IC555 is OK and IC741 is in non-operating, state, then display will blink alternately showing 5 and 7. If IC741 is OK and IC555 is non-operating then display will show 7 in inverting as well as in non-inverting mode.  Moreover it will not flash.


  1. While soldering transister check the base, emmiter and collector with multimeter.
  2. While soldering diode take care for anode and cathode terminal.
  3. Do not solder IC directly on PCB. It may get spoiled due to leakage current from the soldering iron.
  4. While soldering condenser on pin no. 6 of IC 555 take care for the polarity.


PCB [Code 5TP17]=1


12K=1, 68K=1, 10K=2, 1K=8


4.7mfd/16V=1, 47mfd/16V=1


IC 555 =1, IC 741=1, IC SOCKET [8Pin]=2, LED =2

FND [LT542/FND507]=1, Push To ON Switch =1, DPDT Switch =1


Cabinet = 1

DC Battery [9V] =1