How to find where signal enters an amplifier? (specifically in an organ)

[Wheres_my_chippy]

I bought a chord organ recently and I wanted to do some modifications to it but I need to know how to find where the line level signal enters the amp. (Sorry, it might be a simple question but I usually rely on schematics and instructions).

What I am trying to do is put an effects loop (for reverb and other audio effects) in the circuit right before it hits the amplifier. I was also wondering what 1/4 in telephony jacks that bypass when nothing is plugged in are called.

Thanks!

[Andy Watson]

I bought a chord organ recently and I wanted to do some modifications to it but I need to know how to find where the line level signal enters the amp. (Sorry, it might be a simple question but I usually rely on schematics and instructions).

I would look at or around the volume pot (assuming it has one).

What I am trying to do is put an effects loop (for reverb and other audio effects) in the circuit right before it hits the amplifier. I was also wondering what 1/4 in telephony jacks that bypass when nothing is plugged in are called.

Switched jacks? Usually stereo 1/4 inch with break-contacts. Be careful about specifying "telephone jacks" - the end terminal (tip) is often reduced in diameter compared to the standard musician's jack plug.

[Wheres_my_chippy]

Thanks, it does have a volume pot (foot controlled) which I was considering replacing with a variable resistor. Also I had no idea about the jacks, that's really helpful.

Is there any way I could use a multimeter to confirm that I found the audio source? i.e. Would checking for voltage spikes when I press down keys work?

[atferrari]

I would use the DMM to measure continuity first, to see who connects to whom.

[Andy Watson]

Is there any way I could use a multimeter to confirm that I found the audio source? i.e. Would checking for voltage spikes when I press down keys work?

Possibly, depends on the meter. I would try measuring the voltage across the pot on both A.C and D.C. If it's an A.C signal (the one you want)  it will not show much when the meter is set to D.C. (although it probably won't show a great deal on A.C.). If the meter says there is no D.C. potential there then connecting to, or in place of the pot should work. However, if the meter shows there is a continuous D.C. potential, you probably need to look elsewhere. It's difficult to be certain.