Guide for installing the 2600RGB into a Atari 2600 Junior.

This guide is for version 2 of the 2600RGB board. You can find the version 1 guide here.

Tools and materials required:

• Soldering iron and leaded solder wire.
• Insulated copper 'hook up' wire. It's better to use wire that is thin and easy to work with.
• Solder sucker or desoldering iron.
• Pliers and cutters and screwdrivers and tin snips.
• Drill with a 12mm step drill bit.
• Two part epoxy glue (Araldite or similar).
• Electrical tape.
• Hot glue gun.

Click on the pictures to make them bigger.

	Look at all the parts you get! 40p dual wipe IC socket (not used) 40p round pin IC socket (not used) 7 wire ribbon cable 350mm 3.5mm audio socket 8p mini-DIN socket with pin label board for RGB video 4p mini-DIN socket with pin label board for S-video (not used in this guide) pair of 20p 11.5mm pin strip (not used) mini panel mount pushbutton power supply board 3p right angle pin header for power supply diode board and 2 diodes yellow 100nF plastic capacitor (not used) 3.3k resistor
	In addition to the above, 2600RGB board
	And the junior flex adapter.
	There are five solder jumpers on the version 2 board. JP2 - TIA type. Open for NTSC, closed for PAL. If in doubt, the part number for the NTSC TIA is C010444, while the PAL is C011903. JP4 - LED disable. Close this jumper to turn off all the LEDs on the 2600RGB board if they bother you. JP5 - Test mode. Close this jumper to enter test mode. Read more about test mode here. JP8 - Sync mode output for the CS# pad. Open is for TTL, closed for 75 ohm. For best results, close this jumper and use cable with no components in series with the sync signal inside the cable. If you must use a cable with a series resistor in the cable (such as some Nintendo RGB cables) then this jumper must be open. It is always safe to connect CS# directly to a 75 ohm video input regardless of the state of this jumper. JP9 - Low pass filter enable. Open leaves the filter off, closed turns it on. For EMC reasons it's best to have it on. It doesn't really matter much either way.
	Take some screws out of from the bottom. Most of the motherboard is covered by a metal RF shield. Normally there is another, separate metal piece over the RF modulator section to the right, but I seem to have lost that one.
	The two halves of the metal straightening the little tabs on the underside. The TIA (Atari graphics chip) is the 40 pin DIP package closest to the edge of the motherboard. The NTSC version is labelled C010444 or UM6532. The PAL version is labelled C011903 or UM6526P1.
	PAL consoles only: Locate R31, the resistor connected between pin 6 of the TIA and +5V. The PAL junior model has a 10k (brown-black-orange) resistor fitted, but in the PAL version of every other Atari 2600 model this is a 3.3k (orange-orange-red) resistor. The wrong value appears to been fitted by mistake here. For correct operation of the 2600RGB board, this resistor must be replaced with the 3.3k value one supplied in the kit. The NTSC version console is not affected as the NTSC version of the TIA does not use the pin 6 output.
	This is where the 2600RGB board should be mounted. Above the motherboard, between the two grey capacitors C27 and C29. Capacitor C29 may need to be bent to the right slightly to allow the 2600RGB board to fit. Before the 2600RGB board is mounted it must be prepared.
	Find the flex adapter. One side is slightly narrower and is marked "FACE 2600RGB UNDERSIDE".
	Solder the flex adapter in place to the underside of the 2600RGB board as shown. Only the pads with labels need to be soldered.
	The other end of the flex adapter fits between the pins of the TIA on the underside of the motherboard. Make sure it is aligned correctly and solder it in place. Only the pads with labels need to be soldered.
	Carefully turn over the tethered pair of boards then go and fetch your sharpest pair of side cutters.
	There are four signals that must be routed through the 2600RGB board for it to function correctly. The signals are RDY, CLK, D1, D2, D3, which connect to TIA pins 3, 11, 15, 16, 17 respectively. TIA pins 3, 11, 15, 16, 17 need to be cut in such a way as to disconnect them from the motherboard. A wires is soldered to each of these pins, the other end of which is soldered its associated pad on the 2600RGB board, RDYT, D1T, D2T, D3T, respectively.
	Position the cutters around the pin. The cut should be made slightly below the bend in the pin. Once the pin is severed press down on the cutters and bend the cut off part of the pin down to the motherboard. Avoid placing any stress on the remnant of the pin on the chip.
	TIA pins 3, 11, 15, 16, 17 have been cut. (in the photo pin 11 has not been cut yet)
	Solder 55mm long tinned wire to each of the five TIA pin stubs. It's helpful to use wires of different colours of you have them.
	Place the 2600RGB board over the motherboard as shown. Solder the wires from TIA pins 3, 11, 15, 16, 17 to the equivalent TIA pads on the 2600RGB board. Close solder jumper JP2 if this is a PAL console (that is, a PAL TIA is fitted). Leave it open for NTSC.
	To hold the 2600RGB board in place, I recommend two blobs of hot glue where the arrows indicate. Just avoid getting it on the wires or flex adapter. Hot glue is good because it will hold the board in place and may be removed in future if necessary.
	Strip the insulation from the seven wire ribbon cable. Tin the wires with solder and do the same to the pads labelled EXTRA on the 2600RGB board. Solder the wires by holding the ribbon in place and applying pressure with the soldering iron tip, one at a time.
	On the other end of the ribbon cable, strip and tin the wires, making the wire soldered to pin 7 a bit longer than the rest.
	Wires from the Extra connection pins 3-7 connect to the left joystick port.
	Wires from the Extra connection pins 3-7 connect to the left joystick port. Cut the ribbon cable to length and wire it to the left controller port according to the wiring diagram. The pin listing for the Extra connection is, Reset (switch) Select (switch) Right (left joystick) Left (left joystick) Down (left joystick) Up (left joystick) Fire (left joystick)
	For reference.
	The RGB video output connection needs to be mounted somewhere. The most reasonable space seems to be at the side of the console. Use a step drill bit to drill the 12mm hole for the 8 pin mini din connector. Before drilling, screw both halves of the shell together. It's no problem if part of the hole is cut into the bottom half of the shell. As long as it's mostly in the top half it will be fine. Use two part epoxy glue to hold the mini din connector in place.
	Mount the audio jack socket and palette switch if required.
	Wire up the audio/video output connectors according to the 2600RGB wiring diagram. Now is a good time to test the console. Remember that you need the top shell fitted to be able to insert most cartridges into the cartridge slot.
	Unstable clock workaround for PAL consoles. The clock signal from the motherboard is not stable enough for the version 2 of the 2600RGB board when mounted this way. The current solution is to use the supplied clockfix board to buffer the clock signal
	Solder tinned wires to the clockfix board.
	Locate the CPU clock circuit which has a 3.546894 MHz crystal. There is a 100 ohm resistor R12 is series between the output of the clock circuit and the TIA.
	Remove the resistor and solder the clockfix board in its place.
	Unstable clock workaround for NTSC consoles. Since the 2600RGB board has its own NTSC frequency internal oscillator, just set the Auto-clock option in the on-screen menu to '3' which will force it on always. This way it the original oscillator on the Atari motherboard is not used.
	Put the metal shield back on now. You will need to cut some holes in to it for the wires to escape.
	Also, place some electrical tape around the parts of the metal shield which will contact the flex adapter. This may not be strictly necessary, but it's a good idea in case the shield has a sharp edge.
	The last thing to do is replace the linear voltage regulator with a more efficient switch mode type. This is required because the console requires more power to operate with the 2600RGB board installed. If the linear regulator was left it place it may overheat after a while. Find the linear 7805 three terminal regulator and remove it from the motherboard. Clean the solder out of the holes with a solder sucker. Bend the metal shield away from the area to allow the switching regulator to fit. Then insert the 3p right angle pin header into the regulator holes as shown, bent part into the motherboard. Align the short end of the header with the pads on the switching regulator and solder them into position (don't solder to the motherboard yet).
	Make sure the area is clean and dirt free. Remove the plastic which covers the sticky adhesive on the back of the switching regulator. Stick it to the motherboard and solder the pins.
	The pins of the switching regulator are labelled I for input, G for ground, O for output. After you have stuck and soldered it in place, I recommend testing the ground connection with a multimeter. Measure the resistance between a ground point (such as the large copper plane beneath the regulator) and the G pad to check it is close to 0 ohms. If it is not connected please solder again. The Atari may be damaged if it is powered on and the regulator is not connected properly. That's it. Put the console back together.
	Now to install the extra button on the controller. When pressed, it will assert the left and right joystick signals simultaneously. The Extra button is pressed while performing another action. This normally impossible combination of signals is detected by the 2600RGB board. Extra + Up = Select. Extra + Down = Reset. Extra + Fire = Palette switch.
	Drill a 5mm hole (twist drill bit is fine) to in the joystick and mount the pushbutton in a convenient spot. Solder the two diodes to the diode board and install according to the wiring diagram. You can mount the diode board with double sided tape or similar. There are five pads on the diode board. Button, Ground, Ground, Left, Right. Solder the pushbutton between the button an ground terminals. Then solder the ground, left, and right terminals to the joystick board. You can identify the ground connection easily because it's the only one that connects to all the switches. The left and right points should be obvious from looking at the board layout.

Change Log
28/06/2025 - Page Created.