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!

We've gotten spoiled now, used to be that all you could get was photo-copies, which were usually at best, on par with this one.   
This one if from '98, so probably taken from a copy or early tech scanner and that will be as good as it gets.
The only thing I have any issue with is the labeling of components on the 'pictorial'.  If they are not labeled on the board itself, that can make things more time consuming.

Maybe not. Weird. It looks better before uploading it?

I think this one is better.