Fender AB763 Super Reverb - What mod is this?

[Pavels07]

Hi all,

I have an AB763 on the bench for a once-over and I've encountered something I have never seen before. The circuit appears to be mostly untouched, except for a pair of jacks, 1uf 50v electro caps and 2 watt 39k resistors.
They are tied into Tab 1 on the volume pots for each channel (pics attached below).
I don't know what their purpose is, nor does my customer. I am most likely going to remove them and revert the amp back to stock since these were clearly an add on and not crucial to the operation of the amp. I wanted to throw this out to the Board Brain Trust to see if anyone knew what this is/does. My best guess is parallel inputs, because where it is in the circuit doesn't make sense for an effects loop...

[pdf64]

My guess is that they’re somewhat ill conceived line outs.

[stratomaster]

Maybe an attempt to cascade the channels.  Out from normal channel added jack and into the low input on vibrato channel (high input might get wild quickly). 

I'd probably try that just out of curiosity.