[SOLVED] BC547 or BC557.. which must have been here??

• Jan 10, 2012

• #1

H

Hussainb

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hello respected members,

I have got a cfl inverter to be repaired by a friend, while inspecting the circuit, I found out that a transistor has been removed by a previous repairer, he quoted a higher repair price and the friend refused, so i think he must have removed the component so that no one else could perform the repair and have to return to him, anyways....

In the whole circuit, only BC547 and BC557 have been used, so i suspect that a trans from these two must be used here too....

But i am unable to figure out which one... 547 or 557...

Is there some way to identify by the circuit config which trans must have been used...or any other idea you could suggest...
its near an lm324... I cant provide more info about the connections as there are a whole lot of resistors and maze tracks..

your help would be really appreciated...
thankyou

attached images of the pcb



backside

 

Last edited: Jan 11, 2012

• Jan 10, 2012

• #2

mister_rf

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Some photos will make it much easier to help you get your inverter repaired.

 

• Jan 10, 2012

• #3

tpetar

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BC557 is PNP, BC547 is NPN to see what is this transistor reconstruct circuit from existing PCB on paper, then you will know.

Look silk mask on top of PCB if something is written.

 

• Jan 10, 2012

• #4

H

Hussainb

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mister_rf said:

Some photos will make it much easier to help you get your inverter repaired.

Click to expand...

I though so...
Its not quiet possible now in this artificial lighting... will do it first tomorrow in the beautiful natural day light :smile:

 

• Jan 11, 2012

• #5

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Hussainb

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mister_rf said:

Some photos will make it much easier to help you get your inverter repaired.

Click to expand...

ok here are the photos..... i really hope someone can guess this

 

• Jan 11, 2012

• #6

mister_rf

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Please one more picture to include PCB back side layout.

 

• Jan 11, 2012

• #7

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Hussainb

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mister_rf said:

Please one more picture to include PCB back side layout.

Click to expand...

i have added the backside img ......

 

• Jan 11, 2012

• #8

mister_rf

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Emitter tied to GND so that's a NPN transistor...
BC547 = NPN

 

• Jan 11, 2012

• #9

varunme

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you people are amazing , just looking at photograph of the product, the routing is identified

 

• Jan 11, 2012

• #10

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Hussainb

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varunme said:

you people are amazing , just looking at photograph of the product, the routing is identified

Click to expand...

Ya its truly amazing...
I read another post (cant find it now and cant remember the contents clearly now) by someone named jenny asking for an unknown component and mister_rf helped like he had got sixth sense what the asker was talking about...and then she asked something about some camera circuit and mister_rf provided the photo and ckt diag before the asker could put it on... even she was surprised...
what i see is there are quiet a few people truly knowledgeable and humble enough to help someone... and i think edaboard has got many of them!!!!!!!!!!!!

 

• Jan 11, 2012

• #11

mister_rf

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@varunme
I'm afraid I don't quite understand what your are getting at, but that's exactly what we have done... :roll:

 

• Jan 11, 2012

• #12

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Tipu606

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the T30 missing transistor outline is drawn on the circuit board
Now a BC547(NPN) or BC557(PNP) has collector terminal on the left, base in the middle and emitter on the right side if we look at the transistor from the front
Now see where is the solder side connection is going on the emitter terminal on PCB
If it goes to circuit ground then the transistor is BC547 an NPN

 

• Jan 11, 2012

• #13

mister_rf

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The LM324 opamp circuit pin 11 share the same PCB circuit for T30 missing transistor emitter. And that's the GND... any more suggestions? :smile:

 

• Jan 11, 2012

• #14

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Hussainb

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wow... and i thought it wasnt possible to find out what a component can be if its missing... i only know how to check if components are faulty or ok...this has thought me a different view....
thankyou mister_rf and tipu electronics for such wonderful explanations...

 

• Jan 11, 2012

• #15

varunme

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mister_rf said:

@varunme
I'm afraid I don't quite understand what your are getting at, but that's exactly what we have done... :roll:

Click to expand...

nothing mister_rf, i discribed the talent , you people are having, wonderful...