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About Repair History

By on December 24, 2010

For the past one week ago i had been supporting one of my buyer on electronic repair. He told me that he was fixing an amplifier and do not understand why the power transistors and some resistors were getting hot even though he had checked all the components in it. I was puzzle too because usually one would easily locate the bad parts if one have check on all the components in the amplifier. This morning i got an email from him telling me that he have solved the problem and this is what he wrote

Hi Jestine,

Thanks Jestine,I have solved the problem,this amplifier was sent by the customer to his repair friend before he send it to me for repair.When I observed carefully I found that the power transistor should be arranged as PNP-NPN-NPN-PNP and not NPN-PNP-NPN-PNP as what I received from the customer ,his repair friend wrongly put in the transistors….that make me headache.Now the amp back to normal. Thanks


The moral of the story here is that one has to check the background of the set that you are repairing because it could have been repaired by someone before. The repair tech could be inexperience, wrongly replace the components or purposely doing this so that if he can’t repair the set, he also do not want other people to successfully repair it.



  1. Bernard

    December 24, 2010 at 11:55 am

    Hi Jestine,

    You are correct I heard one example from a CRT Monitor repair technician, a CRT monitor was brought to him to repair and the truth is the set was repaired by another technician when the set brought to him for repair a condenser exploded when switch on because of wrong polarity + to - . So I agree with your comment: purposely doing this so that if he can’t repair the set, he also do not want other people to successfully repair it.

  2. Humphrey Kimathi

    December 25, 2010 at 3:10 am

    You are right Jestine, this is one of the biggest challenge i usually encounter in my electronics repairs. usually equipment from other Technicians are hardest to repair due to various reasons, component replaced with wrong ones and therefore if you find it shorted you will definitely replace with the same and hence the machine will never work unless you have the circuit diagram of the same. printed circuit abused by not using good De-soldering equipment, others also use jumpers when the find a resistor Burnt and hence end up doing more harm to the equipment.
    To deal with this problem i usually scan thoroughly for any previous replaced component and make sure they are supposed to be there before i even start troubleshooting.

  3. admin

    December 25, 2010 at 6:17 am

    Hi Guys

    I personally have came across Monitor set that have this kind of problem.



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