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Roxbury
29th December 2011, 07:50 PM
Atari 2600 JR S-Video Mod

Parts Required:


20 column x 13 row Vero board
1 x 4.7k resistor
1 x 9.1k resistor
1 x 18k resistor
1 x 750 ohm resistor
1 x 2k resistor
4 x 75 ohm resistor
1 x 1.6k resistor
1 x 10 ohm resistor
1 x 6.8k resistor
1 x 100uF capacitor
1 x 10uF capacitor
2 x 2n3904 transistors
1 x diode (any value)
1 x 470pF capacitor
1 x S-Video socket
2 x RCA sockets (for composite & audio)
Variety of hook up wire


Creation of the circuit

The schematic for the circuit is as follows:

http://tehkella.net/damian/Atari2600JR/pic_4.png

The following diagram illustrates how to create the circuit on a piece of 20 column by 13 row Vero board.

http://tehkella.net/damian/Atari2600JR/pic_5.png

You cannot use a bigger piece of Vero board as it will not fit. To cut the Vero board to size, use a metal ruler and a sharp stanley knife to score a deep groove along the board, allowing you to snap the excess off.

http://tehkella.net/damian/Atari2600JR/pic_6.jpg

Methodically solder the components onto the board as illustrated. Pay attention to the polarity of capacitors, and the transistors. For the components which have both legs in adjacent holes, orient the component vertically rather than horizontally across the board. See the picture of the completed circuit below:

http://tehkella.net/damian/Atari2600JR/pic_7.jpg
http://tehkella.net/damian/Atari2600JR/pic_8.jpg

Console Modification

Turn the console upside down, and remove the 5 screws.

http://tehkella.net/damian/Atari2600JR/pic_1.png

When opening the console, the upper half is connected by a flat cable. Remove the cable to separate the top half.

http://tehkella.net/damian/Atari2600JR/pic_2.png

The cable can be easily removed by pulling out.

http://tehkella.net/damian/Atari2600JR/pic_3.png

To remove the motherboard from the lower casing, squeeze out the small tabs located on the left and right hand sides.

http://tehkella.net/damian/Atari2600JR/pic_9.png

Flip the board upside down. See the small tabs as highlighted in red. Using a set of needle nose pliers, carefully straighten the taps in order to remove the upper and lower shielding.

http://tehkella.net/damian/Atari2600JR/pic_10.png

As indicated by the red square, this is where the S-Video circuit can be mounted.

http://tehkella.net/damian/Atari2600JR/pic_11.png

It is a good time to plan where you are going to mount the RCA & S-Video sockets. It is easier to reassemble the console if you mount the RCA sockets in the lower half of the casing. However by mounting on the lower part of the case you may need to hack away some of the motherboard. The console this S-Video mod was performed on already has RCA sockets mounted in the top part of the casing. The S-Video socket ideally can be mounted by removing the RF socket in the top right hand corner.

Now for attaching the S-Video circuit to the console. Refer to the picture below:

http://tehkella.net/damian/Atari2600JR/pic_12.png

Sync ? R51, upper side
Lum0 ? R52, upper side
Lum1 ? R49, upper side
Lum2 ? R53, upper side
Colour ? R29, bottom side
Audio ? W2, upper side
5V ? R34, upper side
Ground ? Pad to the left of W1 (check with multimeter)

Now attach all of the wires to the S-Video circuit. Use a different colour for each, and remember to note which colour you are using for each signal. The length to use for each wire will depend on how you route the wires. See the picture below for an indication of how this was done for this mod. Please note the highlighted area ? these wires need to be routed as close as possible to the right hand side side away from the cartridge slot to allow the top casing to fit.

http://tehkella.net/damian/Atari2600JR/pic_13.jpg

For each wire, measure out how much length you need to get from the S-Video circuit in situ to get to the relevant point on the motherboard. Cut each wire with a couple of extra cms, which can be cut back when finally attached. Once you have all the wires attached to the S-Video circuit, place double sided tape to cover the underneath of the Vero board to both insulate it and attach it to the Atari motherboard.

Attach the circuit to the motherboard, then route the wires to the corresponding points on the motherboard. Cut the wires to size, then strip a mm or 2 from the end, tin it then solder to the corresponding point. Once you have attached all wires, either use cable ties or hot glue to help keep the wires neatly together in the desired route.

To get audio, attach a wire to W2, upper side. See in the picture below how the audio wire has been routed, using hot glue to hold in place.

http://tehkella.net/damian/Atari2600JR/pic_14.jpg

The metal shielding can now be replaced. Firstly, a hole needs to be cut in the top shielding as picture. The hole needs to be big enough to let the wires through.

http://tehkella.net/damian/Atari2600JR/pic_15.jpg

If you have the audio wire routed as pictured, place it through the hole as pictured before securing the upper and lower shielding back on the motherboard.

http://tehkella.net/damian/Atari2600JR/pic_16.jpg

Now that the shielding has been re-attached this is what things should look like at this stage. Notice how the wires are routed through the hole in the metal shielding.

http://tehkella.net/damian/Atari2600JR/pic_17.jpg

Now it is time to connect to the S-Video and RCA sockets. Refer to the diagram below.

http://tehkella.net/damian/Atari2600JR/pic_19.png

Connect the Chroma & Luma wires to the S-Video socket, and attach second wires to the S-video socket to run through to the Composite RCA socket.

http://tehkella.net/damian/Atari2600JR/pic_18.jpg

Connect the S-Video & RCA socket ground wires. You can get ground from the following points as pictured:

http://tehkella.net/damian/Atari2600JR/pic_21.png

A switch is required to disable Composite when S-Video is being used. If this is not done, the S-Video picture is affected. The easiest way to do this is to use the Channel switch, on the rear left of the console. Turn the board upside down, and de-solder the switch. Note that this switch can be re-used, so don't cut it off the board:

http://tehkella.net/damian/Atari2600JR/pic_25.JPG

Once desoldered, turn the board back over.

http://tehkella.net/damian/Atari2600JR/pic_26.JPG

To mount the switch, turn it upside down and secure it in place with hot glue. To connect the 470pf capacitor between Chroma & Luma I used a small piece of Vero board as pictured, again using double sided tape to both insulate and keep in place. To connect the switch to disable Composite, connect a wire from Chroma after the 470pF capacitor, and connect it to the middle pin on the switch. Connect a wire to either the left or right terminal on the switch, and run that along to the Composite RCA jack to connect with Luma. Use glue or cable ties to keep the wire runs in place.

http://tehkella.net/damian/Atari2600JR/pic_27.JPG

Now connect the Chroma & Luma wires together and attach to the composite socket. Attach the S-Video socket in place using screws if you have a socket with mounting holes, or hot glue if the socket does not have mounting holes.

Carefully place the top cover back on, ensuring that any wires or components are not in the way. Screw the console back together, and now try out your new S-Video & Composite mod!

http://tehkella.net/damian/Atari2600JR/pic_28.JPG

http://tehkella.net/damian/Atari2600JR/pic_24.jpg

vcoleiro1
29th December 2011, 07:58 PM
Great stuff , thanks for sharing that

mamejay
29th December 2011, 08:24 PM
Excellent write up Roxbury!!
You are pumping out the mod guides now. Sticky will be updated now.
I actually have a more condensed PCB to make up a diagram for.

One thing. Have you added a switch to disable composite AV as having both s-video and composite can degrade the image a bit. I normally desolder the channel select switch and flip this over and hot glue it down and use this to disable the composite.

Roxbury
29th December 2011, 08:30 PM
One thing. Have you added a switch to disable composite AV as having both s-video and composite can degrade the image a bit. I normally desolder the channel select switch and flip this over and hot glue it down and use this to disable the composite.

Didn't know about that. Have now updated the guide to include this.

Roxbury
13th October 2013, 08:35 PM
To keep this consistent with the Atari 7800 mod guide here is how to adjust the brightness of the output for this mod.

Replace R4 (750 ohm resistor) with a 10K Trimpot. Adjusting this trimpot will alter the brightness of the output. On my console I found the output to be too dull with the 750 ohm resistor, but other people who have performed this mod have had a good picture with the 750 ohm resistor at R5.

I played my Svideo modded Atari 2600 today and I must say it looks very good! Very crisp.

Eliminat3r
11th November 2013, 05:20 PM
A big thanks Roxbury for this guide. I performed this on my pal Atari 2600jnr and it worked perfectly! Thanks heaps! It's amazing how good the graphics look on the old 2600 after doing mod.

For anyone else looking to do this mod, I purchased everything I needed from Jaycar.

jacl3
20th May 2017, 01:50 AM
I realize this thread is years old but I just wanted to thank you for your work. I just did this modification to my NTSC 4 Switch 2600 and it worked, of course I soldered it to the NTSC equivalent of the traces off the TIA but I built the circuit itself exactly as you explained and it works great! I was unable to get my 2600 working in color prior to this!