Need help installing transistors properly

[z-adamson]

Working on pioneer sx-1250.

I have my new transistors.

However, I am having dificulty looking at the screening on the board and determining with 100% certainty which lead goes where.

I have the data sheet for the new transistors, I know which leads are emmiter, collector, base, but some of the transistors that I am replacing are not labled for E,C,B and on those transistors I am not sure how to proceed.

The transistors I a n installing are NPN Epitaxial Silicone Transistors, made by Fairchild.

Is there some guide out there explaining what the board screenings mean? See pic for the screening I am working with.

 

[gadget73]

Look up the datasheet on the originals and verify the pin config. Once you know it, use colored pens to code the board and make sure your new ones match up. The pinout isn't always the same, so you may end up with the new parts rotated relative to the old, or with the legs crossed to make it work.

 

[z-adamson]

Look up the datasheet on the originals and verify the pin config. Once you know it, use colored pens to code the board and make sure your new ones match up. The pinout isn't always the same, so you may end up with the new parts rotated relative to the old, or with the legs crossed to make it work.

Tried that, it's not so simple. No numbers on them.

 

[z-adamson]

So, looking at the board, it's for the circle with the lines and the arrow.

The line in the circle with the arrow is emmiter, right?

Middle lead of the teansistor is going to be collector, right?

The remaining leg will be base

 

[z-adamson]

This is what the screening looks like and I marked it E,B,C.

Do I have it right?

 

[fernarias]

That's correct

 

[Alan0354]

What is the transistor you are trying to replace? you need to look up the pin out of the old transistor and try to match the new one by twisting the leads. KSC1845 has pinout different from common transistor, so you have to be careful.

I cannot see the silkscreen on the pcb in your picture. Can you take a close up shot of the transistor you are trying to replace?

 

[Goldie99]

You do also need to be wary of mistakes in how the pcb is marked - they are not always correct and mistakes are quite common.

Use the schematic to identify what the E, C, & B leads of any particular transistor should each be connected to, and compare to the pcb itself, e.g., the parts & traces actually there.

 

[slimecity]

As the others state above - do things in this order:

Identify the original transistor by finding the number (ie: TR something usually) in the service manual or schematic,

The above will tell the transistor number. There may also be different transistors actually installed, check this by double checking the actual transistor markings (are there really no markings on your trannies?),

Also, see if there is screening on the PCB to assist with pinout ID,

Use Goldies' advice as above if in doubt re: pinout:

Use the schematic to identify what the E, C, & B leads of any particular transistor should each be connected to, and compare to the pcb itself, e.g., the parts & traces actually there

Using the info above, find the datasheet for the original tranny,

Look for info on a suitable replacement part, ie: by doing a google search or on replacement sites like alltransistor.com,

Find the datasheet for a recommended new replacement, compare the old and new data and make sure the new part meets or exceeds the specs of the former part.

 

[z-adamson]

Thanks guys, got it figured out with your help . Looked up original part number, found data sheets, compared to board screening. Then I looked at the data sheets for new transistors. New transistors were pinned differently than originals which confused me at first. I was expecting direct replacements to be the same.

 

[z-adamson]

Double post

 

[Alan0354]

But it's easy to twist the pin around and fit the pcb. If you worry about leads shorting out, cut a sleeve from a wire and fit through the leads of the new transistor. That will prevent the leads from shorting to each other.