Go Down

Topic: Transistor Substitute? (Read 1 time) previous topic - next topic

polishdude20

I'm making an AM radio from a kit and I need an equivalent transistor.

The one that the kit came with is a  2SC828R and a 2SA564R. In my class we have 2N2222A's  2N3904's and 2N3906's. Would any of these work in it's place? If not then which other ones would work?

Grumpy_Mike

Look at the data sheet for what you have and compare it with what you need (the original transistors).
As it is an AM radio then particularly look at the gain when operating at high frequency in the 5 to 10 MHz region.

polishdude20


Look at the data sheet for what you have and compare it with what you need (the original transistors).
As it is an AM radio then particularly look at the gain when operating at high frequency in the 5 to 10 MHz region.


I think the frequency and gain won't matter because the section that the transistors are in are the audio amplifier section. I mean Im not sure if it won't matter but would something else work for the audio amplifier?

retrolefty

The 2N3904 (NPN) and 2N3906 (PNP) are almost universal replacements for most any small signal applications. Use them and I'm sure they will perform fine.


Lefty

Grumpy_Mike

Normally the gain on audio transistors is a tightly controlled parameter where as it can be a very wide range on general purpose transistors.
Also check what type of transistors you need (NPN or PNP) then need to be the same. Often audio outputs have a complementary pair, that is one of each type with closely matched gains.

polishdude20

Ok so basically I could hear the radio but VERY VERY faintly and only when I touched a point between two diodes.  I can scan and give a schematic tomorrow. But I wired up an NPN on one side and PNP on another side and they arent blowing up so thats good.

And like I said, I can hear the radio but only faintly through headphones and only when I touch a point between 2 diodes, also the volume knob isnt making it quieter or louder just produces a faint scratching noise when I turn it. So basically something is wrong with the amplifying portion of the circuit but until i can show you guys a schematic then you can't help right?

Go Up