HI Karthik,

my question is i experimentally test some common transistors  first i starts my testing work with the transistor BC547it is a NPN TRANSISTOR the first pin is collector and second one is base and the third one is emitter given in the data sheet but iwant to identify it by testing it with analogue multi meter i conduct the test as per the information given by  you in your e book TESTING OF ELECTRONIC COMPONENTS  the testing result shows that it is an pnp transistor but it is actually a NPN TRANAIATOR  after thes result i connduct a switching test it ans wers that it is an NPN TRANSISTOR but  the multi meter fails in testing while doing these test i tes the LED IN CONTUNITY MODE it gives the ANODE AND CATHODE IDENTIFICATION PROPERLY BUT WHEN I DONE THE SAME TEST TES IN OHMIC MODE THE POSITIIVE AND NEGATIVE TERMINALS REVERSED iam not able to identify it and what is the reason for these changes because iam is a beginner and new to this field so i request you to tell me what is the reason for thes problem my electronic friend thank you iam waiting for ur replay

Yes the BC547 is a NPN transistor but may i know what brand of analog meter you are using because some do not have a reverse output polarity. I’m using Sunwa multimeter thus the red probe is actually a negative and black probe is positive.



i’m working with a 4 pin opto iso, part ## is  425 PC817Bi’m not getting this part # in trinidad,, what part # could i use as a substitute????


You can try order from this link:


You can try pc123 as replacement.



Can we buy small amount signal diode from you? I just move to kuantan and have no idea where to find electronic store here.

General diode like IN4148 would be ok. Qty – 30 pcs

HI Kamarul,

I search the web and i called them and they sell the components you are looking for. The address is in Kuantan and please click on the link below:


They even sell TV Flyback.

Have a good day!



Hope you’re well.

Please could you assist with identification of a component. I have looked everywhere without success.

Its markings are STR F6267 SK6527D. It is an IC I’m sure and has 5 legs. I removed it for test from the primary side of a SMPS.

HI Robert,

Yes it is an IC and it can be purchased from the link below:



Comments are closed.