Exsample:Mac LC video connector pinouts:

 Pin Number    Signal Name
 1             RED.GND
 2             RED.VID
 3,15          /CSYNC or /HSYNC
 4             SENSE0
 5             GRN.VID
 6             GRN.GND
 7             SENSE1
 8             n.c.
 9             BLU.VID
 10            SENSE2
 11            C&VSYNC;.GND
 12            /VSYNC
 13            BLU.GND
 14            HSYNC.GND
 Shell         CHASSIS.GND

shown NO.10 to 14 as mini connect to coax line for rear sealded box area. (green).
NO.5,7 to J59,J27 are power SW NO.28 to 34 as connect to internal Plain Talk microphone.(yellow)
ColorClassic standerd 512 x 384 mode is NO4 and 10(DB15) to ground. What same line this connecter...

Sense 0,1,2
Perhaps connect 0,2 to ground or all opened. Require 480x640 mode a sense 0 to ground.

Display             	Pixels   	Hz	Pins grounded
Apple Hi Res RGB    	480 x 640	67 Hz	4
Apple 12" RGB       	512 x 384	67 Hz	4,	10
Apple IIe RGB       	560 x 384	67 Hz    
VGA                 	480 x 640        		10
RS-170A (interlaced)	480 x 640	60 Hz	4, 7

----sample doc-----
The Macintosh LC does not supply vertical synchronization with the Green video signal (pin~5). The vertical synchronization signal is supplied on pin 12.
The Macintosh LC requires that pin 4 (SENSE0) be connected to Ground to signal the connection of a 640 x 480 monitor. The Macintosh LC requires that pin 4 and 10 (SENSE0 and SENSE2) be connected to Ground to signal the connection of a 512 x 384 monitor (i.e., the Macintosh 12" RGB Display). The Macintosh LC requires that pin 10 (SENSE2) be connected to Ground to signal the connection of a VGA monitor. Pin 7 (SENSE1) is grounded in the Macintosh LC.

Change to 480 x 640 mode: replace R78 chip to R79!
Internal audio out put are left-channl only, but a may be able stereo!