Here are wave forms of the 6 signals we are interested in.
The HSYNC signals control the end/start of the lines and the VSYNC
pulses control the end/start of the screen. CSYNC signals
control both (horizontal flyback and vertical retrace).

           ||         ||         ||                                 
.._________||_________||_________||____... HSYNC (active high)      
                                                                    
                                _____                               
                               |     |                              
.._____________________________|     |_... VSYNC (active high)      
                                                                    
                                _____                               
           ||         ||       |     |                              
.._________||_________||_______|     |_... CSYNC (active high)      
                                                                    
                                                                    
.._________  _________  _________  ____...                          
           ||         ||         ||        _____                    
           ||         ||         ||        HSYNC (active low)       
                                                                    
.._____________________________       _...                          
                               |     |     _____                    
                               |_____|     VSYNC (active low)       
                                                                    
.._________  _________  _______       _...                          
           ||         ||       |     |     _____                    
           ||         ||       |_____|     CSYNC (active low)       
                                                             _____
For JAMMA we need the last one (active low version of CSYNC, CSYNC).

The basic equation is that CSYNC is the logic-OR of HSYNC and VSYNC
i.e CSYNC <=  HSYNC OR VSYNC

Everthing else is based on that with the oppropriate inversions.

Most of the old boards I've had to mess with start with active
high H/VSYNC and I need to convert them to active low CSYNC
    _____
i.e CSYNC <= HSYNC NOR VSYNC   (i.e TTL chip 7402)

or you can do it with a NAND gate (chip number 7400) as follows
_____
CSYNC <=  INV(INV(HSYNC) NAND INV(VSYNC))

where INV(A) is (A NAND A) i.e you can invert a signal by feeding it
into both inputs of a NAND gate. Believe it or not this is the one
I tend to use because I had some 7400's sitting around, and you
still only need one chip to do it.

Another hand combination is:
_____    _____     _____
CSYNC <= HSYNC AND VSYNC

Apologies if all this is second nature (or totally confusing). It is
difficult to know how much info to include.

One other thing, if you don't have an oscilloscope, you can figure
out if a HSYNC/VSYNC is active low or high using a analogue voltmeter
(I haven't tried it with a digital voltmeter). Active high HSYNC/VSYNC
will read close to 0V because they are low most of the time. Active
low HSYNC/VSYNC read just under 5V, because they are high most of
the time.