Novice Question - help me understand switching

Beginner Question - please bear with me

I have a korg guitar fx unit that has four foot switches to switch between fx patch's. The fourth switch simply stopped working one day. I pulled the unit open and noticed that next to each switch was a little transistor which I assumed enabled the switching system. The transistor read "A1A4M". I tried everywhere to find a replacement and couldn't. I read some stuff on the net about this transistor and it seemed I could use an NPN small signal transistor instead. So I put in a BC547 and now the fourth switch works but now wont turn off when I stomp on the switch!

It seems to me I don't understand enough about switching with transistors to know what I have done wrong.

Can someone point me in the right direction to read up about this or offer me some info here as a general start to understanding my problem?

Thanks very much and apologies if this electronics 101 question is a bit stupid.

Anyone?

Even just to point me in the direction of where I can read about this?

if you have a schematic of the device and could post it, we could begin to
examine what the problem could be.

otherwise it would be difficult to avoid wild speculation and quessing

A little bit of Googling found me these.....

http://www.diyaudio.com/forums/parts/10622-very-strange-transistors-2.html
http://www.necel.com/discrete/en/images/pdf_e/TC-3685.pdf

Maybe adding the 10kOhm resistors externally to the BC547 (providing it's in the circuit the right way round!) will solve your problem.

Check the switch. You may think that this defeats the purpose of having a transistor switch but not really. Switch turns the transistor on and off for a clickless signal switching.

But if the switch is just a momentary on button then a common application in effect pedals is that, the button controls a flip-flop. One leg of the flip flop would turn on/off a Jfet for signal switching.

Just check the circuit a bit more in depth.