Here's the GX-120 / GX-212 schematic I was referring to.

But you can!
It just needs the proper probe/adapter.
Everyday I measure power transistor current for servicing, power supply current under load, say when playing Music, current through a speaker, etc.
In this case,all it takes is a 0.1 ohm resistor in series with load, and clipping scope leads across it.
It turns 10A peak current into very measurable 1V peak, easy to display on any scope screen.

Warning: you need to have scope ground floating OR to have that resistor with one end grounded.

I used to wonder how they measured current when set 📐 up in x-y mode

So I just accepted it 

So now I think they are just showing voltage. (Ya think ?!?!?  )

And yeah isn't that what oscilloscopes do 

I don't know the complete details I think the volts per division is set to "make it right" I'll see how it's done when I actually do this.  (Eek  )

So what's all the fuss about well in my book 📖 I'm working through the have a sections where students use a Tektronix 575.  I would love to have one but I looked at some and they are big and heavy, have lots of tubes (huh?!?) and $$$$ 

Dont get me wrong I would love to have one 

Now credit to the book 📚 they have instructions how to monitor Ic on the scope which is cool.

Seems like I saw on MEF one of the members here posted some beautiful pics of output characteristic curves 

Although there are about 6 different G100 schematics, all of them basically take the speaker output & resistor the signal down for the record out.
To be specific please advise the exact model amp.

Good!!!
Please post the  GX-120/212 diagram  here se we can also compare them.
Thanks.

*There is* line level signal out of that jack, so it should work.

Please post schematic here so we can check where does that jack pull signal from.

Thank you for that! It confirmed my suspicions about the GX-120/212 diagram since my original GX-65 PDF has the parts list - the 2 boards' component values are the same, minus the locations that show "unused" on the GX-65. For any "mods" (bright switch, multiple channel reverb), I can get the values off the 120's schematic.

Thanks again!

 Hello Forum,
  I've had my Yamaha G100 now for about 4 years. I really love this amp. There is a jack on the back of the head labeled "Record output". Because I have no way of recording with a mic i would like to try using this and I have with no success.
  I believe I'm using or doing something wrong. The schematic says "+4dBm nominal  +31.2dBm max  For 600 ohm unbalanced lines".

So far Ive tried using a guitar cord from the record out to my instrument in jack on my Line6 and got nothing. I didnt want to risk frying anything so thats all Can anyone explain what im doing wrong and how I can properly use this jack. Everything on the amp works perfectly (I bought it used) so I dont think anything is wrong with the amp.

ANY help on this would be greatly appreciated Thank You

Here's a slightly better one from my paper files but only the main schematic.You cannot view this attachment.

Thank you all for your help.

Where should I look for a good "once over" guide for going over it and "refreshing" (i'm thinking things like reflowing solder, etc.), just in general?

Thanks again!