Custom Arcade PCBs -
Arcade Table Workshop

RGB to NTSC Encoder (Rev. 1)

Vision All fans of genuine classic arcade games usually need either an arcade cabinet or an interfacing solution to their exiting tv/display at home. When it comes to non-arcade cabinet solutions, the 15 kHz RGB video signal from JAMMA standard arcade hardware needs to be displayed somehow. In Europe however, most tv sets feature RGB SCART inputs which will usually accept that 15 kHz RGB signal. Arcade classic fans outside of Europe either have to purchase an expensive multisync display or look for video signal conversion solutions. After numerous requests, we have been developing a small encoder circuit which is capable of converting the RGB video output into an NTSC video signal, thus allowing the user to connect a display/tv set via s-video cable.

Solution First of all, we need to design a printed circuit board (pcb) which will host all the necessary components and connectors.
The new encoder should compliment our existing JAMMA Supergun/MAK boards and also be usable on a stand-alone basis. All signal paths on the pcb should be minimized for excellent video quality. The selection of components is crucial as well since lower signal noise will also result in better picture quality.

NTSC Video The first decision was to drop the PAL conversion and go for NTSC-only. The frame rate of JAMMA arcade games is the same as of NTSC video anyway (60 Hz, half-frames) and fans in Europe (where PAL is predominant) still have their RGB SCART input devices.
After several weeks of development, we have been finalizing a pcb layout which meets our high expectations.

Test A couple of days later, we receive a batch of bare multilayer pcbs. After carefully soldering the various components to the board, we are ready for the first tests. Thanks to the small form factor, the NTSC encoder can be plugged directly in our recent JAMMA Supergun/MAK board as well. Some color adjustments are being done with the trimmpots on the Supergun/MAK board. Once this is done, everything is ready to play! The s-video output offers a truly convincing video quality thanks to the seperated crominance and luminance lines The optional composite output has a slightly softer image which was to be expected. Therefore, it is highly recommended to use the s-video output with priority.

Benefits The extensive planning and high Der hohe Aufwand bei der Entwicklung hat sich gelohnt:
The multilayer pcb has minimized signal paths. Thanks to tantal capacitors the signal to noise ratio kept at a minimum. Instead of a simple crystal clock circuit, we have opted for a stabilized oscillator clock which provides a rock-solid timing for the NTSC video output.

Power supply The NTSC encoder needs +5 V power supply. The user can select between two different power sources:
1) A 4-pin Molex type socket is wired according to PC floppy/disk drive standards. Two labeled can be used to connect ground and +5 V lines directly.
2) Power supply can also be provided via the D-Sub video input plug. If +5 V power is being supplied on pin 9 then no other power source is needed to operate the NTSC encoder.
In either case, a red LED will indicate when power is attached.

RGB video
input 15 kHz RGB video input: HD D-Sub 15-pin plug The 15 kHz RGB video input signal can be connected via a 15-pin HD D-Sub plug. Of course, the RGB video output from JAMMA (arcade videogame hardware) is being support. The NTSC encoder can either deal with a single composite sync signal (JAMMA standard) and also with separate horizontal and vertical sync signals on the respective input pins. Both operation modes are user selectable via selector/switch.
The big advantage of this design is the fact that the encoder can plug directly on the RGB video out of our recent JAMMA/Supergun board.
Please refer to the following table for the detailed pin assigned of the RGB video input. Supported pins are marked in yellow color:

Pin	Name	15kHz RGB Video In (JAMMA)
1	Red	Video Red
2	Green	Video Green
3	Blue	Video Blue
4	Monitor ID2	not connected
5	Ground	Ground
6	Ground (Red)	Ground
7	Ground (Green)	Ground
8	Ground (Blue)	Ground
9	Key (no pin or +5V)	User Switchable: +5V Power Input or not connected
10	Synch Ground	Ground
11	Monitor ID0	not connected
12	Monitor ID1	not connected
13	Horizontal (Composite-) Synch	Horizontal or Composite Synch
14	Vertical Synch	User Switchable: Vertical Synch or not connected
15	Monitor ID3	not connected

S-video output This output delivers the best quality of the encoder since the crominance and luminance lines are separated. The video standard of the signal is NTSC.

Composite
output This output also delivers an NTSC signal. the picture quality is slighly inferior compared with the s-video output.

Summary We are quite satisfied with the results of our NTSC encoder project - a small form factor and great encoding quality for everyone who does not own an RGB SCART display/tv set.

The small encoder module is also well suited for "consolized" arcade hardware projects; e.g. when arcade hardware has to be adapted for home use.
Moreover, the new RGB to NTSC encoder can be combined with our Supergun/MAK interface (not included) - just plug into the RGB video output, attach the power supply and there you go!

Specifications:

Input:

RGB video (analogue, 15kHz, 60Hz interlaced) with composite sync or seperate H/V sync via HD D-sub15 plug

Output:

NTSC video (3,58 MHz) via S-video and composite sockets

Sync Select:

CSync or H/V sync input user switchable

Power Supply Range:

+5 Volts (min. +4,75; max. 5,25 Volts)

Power Select:

via Molex type or HD D-sub (pin 9) user switchable

Notice: If you would like to use the RGB to NTSC encoder as a "stand alone" module without our Supergun/MAK interface, then please make sure that the RGB input signal (red, green and blue colors) is adjustable. If you would like to solder your input (or output) lines directly to the board, we can always omit the connector(s), just let us know.

Availability If you would like to have an NTSC encoder for your own arcade projects then we can offer the remaining boards 69,- Euro each incl. VAT. (ask for packaging and shipping costs, please).

This is not a do-it-yourself kit. All boards come fully assembled with all components. We also assure full ROHS conformity of our RGB to NTSC encoder boards. This is a private sale, so no refunds or warranty but no reason to worry: All boards are carefully tested and in working condition. We will also provide four pcb legs and one power supply cable (approx. 50 cm) with each board while supplies last.

If you are interested, please drop us an email:
ofni.regit-repap@ybbob

All references to the JAMMA standard refer to the JAMMA «First Edition».

Errors and omissions excepted. All descriptions and specifications are subject to change without notice.