s2a2_diagram.png (4164 bytes)


Audio/Video Input
I highly recommend the use of official or high quality third party cables. Poor quality cables are often wired incorrectly, break easily, and cause a buzzing sound to be heard through the audio. If you wish to build your own video cables, might I suggest my page of Game Console RGB SCART Cable Diagrams as a reference? Take note that this adapter does ignores the SCART switching voltages on pins 8 and 16.

All pre made SCART cables will used composite video for sync information. If for some reason you would like to connect a device which does not have composite video available (such as an Amiga or other microcomputer) you may want to construct a non-standard cable with a TTL composite sync signal in place of the composite video. There are a set of jumpers located next to the SCART socket labeled TTL and 75.

75 on, TTL off  = Terminated composite video. Default.
75 off, TTL off = Unterminated composite video. Try this if you have any sync related problems.
75 off, TTL on = TTL composite sync or TTL horizontal sync.

The video amplifier will not function without some form of sync input.

The adapter requires a well regulated 12 volt supply capable of supplying at least 1 amp of current. This can be connected via the JAMMA card edge or the terminal block. Other voltage from the JAMMA power supply are not used.

Sometimes switching power supplies have trouble keeping regulation without a load on the +5V line. For these situations you will need to connect a power resistor (supplied) between the +5V line and ground to act as a dummy load. This resistor will get hot so should ideally be connected directly to the power supply, away from stray fingers. power_resistor.jpg (43717 bytes)

Refer to the photo to the right on connect the white power resistor --->


Speaker Output
The speaker must have an impedance of 8 ohms or higher (two 4 ohm speakers in series, or two 16 ohm speakers in parallel are ok) speakers of lower impedance or two 8 ohm speakers in parallel may overload the amplifier. The speaker would normally be wired to the JAMMA but may be connected to the terminal block if desired.

The onboard amplifier is monaural (i.e. has only one channel) which mixes both left and right audio signals together. The speaker must be connected between speaker -ve and speaker +ve, not between either speaker terminal and ground as is normally done with a HiFi amplifier.

The volume control adjusts volume of the sound, as all good volume controls do.

Video Output
Red, Green, and Blue video is output from the JAMMA card edge as well as a composite sync signal. Video and composite sync are also available from the terminal block along with separate horizontal and vertical sync outputs (I hear some pre-JAMMA arcade monitors require sync signals like this).

There are two controls which affect the video signal, contrast and brightness. The contrast control adjusts the amplitude of the video signal, the brightness adjusts the black level. The brightness control is a high accuracy 4 turn trimpot which is pre adjusted to a black level of 0.2V. This is suitable for most monitors and will usually require no additional adjustment. Note that if the black level is set to less than 0.05V the picture may cut out, even with the contrast at maximum. There are is a square test point next to the brightness trimpot. I use this to calibrate the black level but you may use them too, should you wish to do so.

Take note that the contrast can be adjusted higher that the previous model. Be careful not to over drive your monitor.

Audio Output
The red 3.5mm jack above the SCART socket is a buffered line level stereo audio output from the game console. Useful if you feel the built in audio amplifier is far too puny and would like to use something with a bit more heft.

The level is unchanged by the volume control.

Audio Input
The green 3.5mm jack above the SCART socket is a buffered line level audio input. This is a switched jack, so the audio in from the SCART input (if any) will be switched off.



Appendix I: Pin Listings

Terminal Blocks (blue) -
From right to left.

GND Ground
5V +5V Input (not required)
12V +12V Input
HS Horizontal Sync Output (active low)
VS Vertical Sync Output (active low)
SPKR Speaker Output Positive
SPKR Speaker Output Negative
RED Red Video Output
GREEN Green Video Output
BLUE Blue Video Output
CSYNC Composite Sync Output (active low)
GND Ground

Control Expansion Connector

1 Second Player Fire Button 5 2 First Player Fire Button 5
3 Second Player Fire Button 4 4 First Player Fire Button 4
5 Second Player Fire Button 3 6 First Player Fire Button 3
7 Second Player Fire Button 2 8 First Player Fire Button 2
9 Second Player Fire Button 1 10 First Player Fire Button 1
11 Second Player Right Joystick 12 First Player Right Joystick
13 Second Player Left Joystick 14 First Player Left Joystick
15 Second Player Down Joystick 16 First Player Down Joystick
17 Second Player Up Joystick 18 First Player Up Joystick
19 Second Player Start Button 20 Coin Switch 1
21 Coin Switch 2 22 (reserved)
23 Slam Switch 24 Test Switch
25 First Player Start Button 26 OSD Blue Input
27 OSD Green Input 28 OSD Red Input
29 OSD Enable Input 30 OSD Sync Input
31 Vertical Sync Output 32 (reserved)
33 +12V 34 +12V
35 +5V 36 +5V
37 +5V 38 Ground
39 Ground 40 Ground

CTRLEXP1: Terminal Blocks (green)

2PCN Coin Switch 2 1PCN Coin Switch 1
2PST Second Player Start Button 1PST First Player Start Button
2PUP Second Player Up Joystick 1PUP First Player Up Joystick
2PDN Second Player Down Joystick 1PDN First Player Down Joystick
2PLT Second Player Left Joystick 1PLT First Player Left Joystick
2PRT Second Player Right Joystick 1PRT First Player Right Joystick
2PF1 Second Player Fire Button 1 1PF1 First Player Fire Button 1
2PF2 Second Player Fire Button 2 1PF2 First Player Fire Button 2
2PF3 Second Player Fire Button 3 1PF3 First Player Fire Button 3
2PF4 Second Player Fire Button 4 1PF4 First Player Fire Button 4
2PF5 Second Player Fire Button 5 1PF5 First Player Fire Button 5
GND Ground   (reserved)*
GND Ground   Slam Switch*
TEST Test Switch    

* No screw terminals exist for these signals, though they can bee added by request.

CTRLEXP2: JAMMA Pass-Through

Parts Side (top) Solder Side (bottom)
Description Pin Passed through? Description Pin Passed through?
Ground 1 YES Ground A YES
Ground 2 YES Ground B YES
+5V (not required) 3 YES +5V (not required) C YES
+5V (not required) 4 YES +5V (not required) D YES
-5V (not required) 5 YES -5V (not required) E YES
+12V 6 YES +12V F YES
KEY 7   KEY H  
N/C 8   N/C J  
N/C 9   N/C K  
Speaker +ve 10   Speaker -ve L  
N/C 11   N/C M  
Red video 12   Green video N  
Blue video 13   Composite Sync P  
Ground 14 YES Service Switch R  
Test Switch 15 YES Slam Switch S YES
Coin Switch 1 16 YES Coin Switch 2 T YES
First Player Start Button 17 YES Second Player Start Button U YES
First Player Up Joystick 18 YES Second Player Up Joystick V YES
First Player Down Joystick 19 YES Second Player Down Joystick W YES
First Player Left Joystick 20 YES Second Player Left Joystick X YES
First Player Right Joystick 21 YES Second Player Right Joystick Y YES
First Player Fire Button 1 22 YES Second Player Fire Button 1 Z YES
First Player Fire Button 2 23 YES Second Player Fire Button 2 a YES
First Player Fire Button 3 24 YES Second Player Fire Button 3 b YES
First Player Fire Button 4 25 YES Second Player Fire Button 4 c YES
First Player Fire Button 5 26 YES Second Player Fire Button 5 d YES
Ground 27 YES Ground e YES
Ground 28 YES Ground f YES

Appendix II: Electrical Specification

Input Voltage Ratings

Description Min Typ Max Unit
Power supply voltage 11 12 13 Vdc
Red, Green, Blue video   0.7 2 Vp-p
Composite video (JP3 off) 0.7 1 2 Vp-p
Composite sync (JP3 on) 1   5 Vp-p
Max sustained DC voltage into R,G,B,CV input     2.5 Vdc
Left, Right audio 0.2 0.5 2 Vp-p

Input Impedance Characteristics

Description Typ Unit
Red, Green, Blue video 75 Ohms
Composite video (JP2 on, JP3 off) 75 Ohms
Composite video (JP2 off, JP3 off) >1k Ohms
Composite sync (JP2 off, JP3 on) 800 Ohms
Left, Right audio 10k Ohms

Output Voltage Characteristics
Power supply = 12V / R, G, B video input = 0.7Vp-p / CV input = 1Vp-p / L, R audio input 0.5Vp-p
Horizontal, Vertical, Composite sync output load = 1.5k / R, G, B video output load = 1k

Description Min Typ Max Unit
Red, Green, Blue video (AC) (contrast) 0   7 Vp-p
Red, Green, Blue video offset (brightness) 0.1   3 Vdc
Horiz, Vert, Composite Sync logic high 2.5 3   V
Horiz, Vert, Composite Sync logic low   0.24 0.5 V

Other Characteristics

Description Min Typ Max Unit
Bandwidth (-3dB) @ max contrast 50     Mhz
Peak voltage on R,G, B video output (before distortion) 7 7.5   V
Minimum video output black level (before cut out)   0.05   V
R, G, B video output impedance   300   ohms
L, R Audio output impedance   300   ohms
Speaker load impedance 6.5 8   ohms
Power draw (audio amp disabled)       mA
Power draw (audio amp active)     1000 mA
Gain mismatch between R, G, B video     3.5 %
R, G, B video voltage gain 0   7.5  

Appendix III: Resources

Appendix IV: Ordering Information

See ordering page.

Page created 3/1/2011.

Updated 22/8/2012.