Original info from Comos (http://csdb.dk/forums/index.php?roomid=7&topicid=25121)
and Lemon64.com forum post by keropi (http://www.lemon64.com/forum/viewtopic.php?t=52318&postdays=0&postorder=asc&start=12)

Updated 15-09-2017 With clean-ups, corrections and better documentation level by Guru (http://gurudumps.blogspot.com.au)

Modification for Commodore 1084S-D2 monitor to add Digital RGBi mode.
This works with Commodore 128 80 column mode (TTL RGBI) and makes
a 1084S-D2 into a 1084S-D1.
Listed parts are either missing or different on D2.

R242 - remove (in D2 is 330, in D1 is not connected)          Resistor quantities   
R243 - 330 (in D2 is 2K)                                      -------------------   
R245 - 470 (in D2 is wire link)                                    27  = 1         
R246 - 220 (in D2 is 1K5)                                         100  = 1          
R249 - 10K                                                        150  = 3          
R250 - 4.7K                                                       180  = 3          
R251 - 560                                                        200  = 4          
R252 - 560                                                        220  = 1          
R253 - 4.7K                                                       240  = 1          
R435 - 27                                                         330  = 10          
R436 - 2.7K                                                       430  = 6           
R437 - 200                                                        470  = 5           
R701 - 330                                                        560  = 2           
R702 - 330                                                        680  = 1           
R703 - 330                                                        820  = 4           
R704 - 470                                                        1K   = 3           
R705 - 470                                                        2.7K = 1           
R706 - 470                                                        4.7K = 2           
R707 - 330 (in D2 is 10K)                                          10K = 1           
R708 - 470 (in D2 is wire link)                                  30/5W = 1           
R709 - 330                        
R710 - 330                        
R711 - 330
R712 - 330                        
R713 - 330                        
R714 - 200                        
R715 - 200                        
R716 - 200                        
R717 - 100
R718 - 820  
R719 - 680
R720 - 430
R721 - 430
R722 - 430
R723 - 180
R724 - 180
R725 - 180
R729 - 1K
R730 - 1K
R731 - 1K
R735 - 150 (if already present on D2, no change needed)
R736 - 150 (if already present on D2, no change needed)
R737 - 150 (if already present on D2, no change needed)
R738 - 820                        
R739 - 820                        
R740 - 820                            
R741 - 430
R742 - 430
R743 - 430
R744 - 30/5W (in D2 is wire link)                    
R745 - 240                        

C701 - 100nF (code=104, polyester or ceramic)
C702 - 100nF (code=104, polyester or ceramic)
C711 - 1.5nF (code=152, polyester or ceramic)
C704 - 10nF - normally no change needed (code=103, polyester or ceramic, if already present on D2, no change needed)
C423 - 2.2uF/50V electrolytic
C229 - 10uF/16V electrolytic
C332 - 10uF/16V electrolytic

J73 - remove 24K resistor and place wire shortcut between the two points

There are a large number of equivalents for transistors.
Use https://alltransistors.com or http://www.semicon-data.com to search for substitutes.
Q203 - 2SC1815
Q401 - 2SC1815
Q701 - 2SC1959 (2SC9013 is compatible but pins 2 & 3 must be swapped)
Q702 - 2SC1959 
Q703 - 2SC1959
Q704 - 2SC3337 (2SC2570 can be used as a pin-compatible alternative)

I202 - 74LS86
I403 - LM7805. Remove the wire link between pins 1 & 3 on D2, add 7805 and a heat sink. make heat sink from a piece of metal.
I701 - 74LS06
I702 - 74LS06

add SW1 (4PDT mini push switch latching type. Switch has 2 rows of 6 pins, 12 pins total)
        Here's an example.... http://www.altronics.com.au/p/s1520-salecom-4pdt-pcb-mount-mini-pushbutton-switch/
        Also get a knob...... http://www.altronics.com.au/p/h6660-5.5mm-black-plastic-knob-for-s-1520/
add L704 bead (same type as L701/L702/L703) or use a link wire 

D214 - 1N4148
D216 - 1N4148
D404 - 1N4148
D405 - 1N4148
D704 - 1N4148
D708 - 1N4148
D712 - 1N4148 (in D2 is wire link)  
D713 - 1N4148 (in D2 is wire link)  
D714 - 1N4148 (in D2 is wire link)