1200XL video - Clearpic 2002 vs Clearpic II

[oracle_jedi]

Some years back I decided to do the CLRPIC modification to try to fix the terrible video output from my 1200XL.

 

I followed these instructions: http://www.atarihq.com/atcomp/1200vid.html

 

I include the link here as there appear to be several variations on the "sequel to CLRPIC" upgrade, such as this one: http://wolfpup.net/atarimods/1200xl-vm.html

 

Anyway, the result was a sharper image, but the colours were washed out and it also introduces the strange effect that the colours seemed to be offset from the image - everything ended up with a grey shadow to the left.

 

I recently decided to see if the newer upgrades were any better, so found the Clearpic 2002 modification: http://www.retrobits.net/atari/clearpic.shtml

 

Before I could do that I needed to figure out what I needed to put back.

That was pretty simple - R187 needed a 1M Ohm resistor and R188 needed a 750 Ohm resistor.

The Clearpic 2002 steps for CR19, C60 and C119 could be skipped as they were already done.

 

 

The result is quite remarkable.

 

The image is still sharp, but now the colours are far more vivid (as vivid as they can be on NTSC) and the colour synching problem has completely gone.

 

Anyway I thought I would share in case anyone else with a 1200XL with an older Clearpic mod is wondering if the newer version is worth the effort - it most definitely is.

 

Thank you again Bob Woolley (and also Dan Vernon for a great HTML version).

[spookt]

Hi Jedi

 

Thanks for the link and the recomendation. I think I'm going to try this on my 1200XL.

 

BTW - Can anyone explain how to add 75Ohm resistors as terminators in an A8 -> SVID cable? I built a cable for my 800XL and it does have some issues when hooked up to the TV this way. I get image distortion on bright hues etc. Could this be down to over driving the TV?

 

Cheers

Paul

[+bob1200xl]

I think if you do the 2002 ClearPic, your s-video will be OK. I used a small mini-box to mount RCA connectors to a s-video cable. The 75 ohm resistors are mounted in the box. If you only have a cable, it's going to be tough. How did you do the 800XL? Is it modified?

 

Bob

 

 

Hi Jedi

 

Thanks for the link and the recomendation. I think I'm going to try this on my 1200XL.

 

BTW - Can anyone explain how to add 75Ohm resistors as terminators in an A8 -> SVID cable? I built a cable for my 800XL and it does have some issues when hooked up to the TV this way. I get image distortion on bright hues etc. Could this be down to over driving the TV?

 

Cheers

Paul

[spookt]

How did you do the 800XL? Is it modified?

 

Hi Bob

 

So far I've only added the missing video line to the monitor jack and then built an SVID cable. How do the terminators work? Sorry if my electronics inexperience is showing. I'm slowly getting back into it after 20 years away.

 

The only other mods on this 800XL are a 32in1 from classics and a 256Mb expansion which was in there when I acquired it. I think it's a Newell.

 

Thanks for the help.

Paul

[STGAC]

You just connect the resistors between the LUMA and ground and CHROMA and ground. The Atari puts out too much signal for some of the s-video inputs. The resistors draw down the voltage to an acceptable level. They are supposed to terminate the video coax but that is secondary, really. Problem is, if they are missing you may get too much voltage.

 

How did you 'add the missing line'?

 

Bob

 

 

How did you do the 800XL? Is it modified?

 

Hi Bob

 

So far I've only added the missing video line to the monitor jack and then built an SVID cable. How do the terminators work? Sorry if my electronics inexperience is showing. I'm slowly getting back into it after 20 years away.

 

The only other mods on this 800XL are a 32in1 from classics and a 256Mb expansion which was in there when I acquired it. I think it's a Newell.

 

Thanks for the help.

Paul

[spookt]

I looked in this thread (thanks to mimo for pointing me at it) and did just this bit:

 

Missing Chroma Output

On the bottom of the board, solder a 100-ohm resistor to the junction of R67 and R68 (the right side in the picture, looking at the top of the board) and put a piece of tape under the resistor to insulate it from the board. Solder a wire from the other end of the resistor to pin 5 of the DIN connector (bottom-left pin from the back).

 

Except I used heat shrink on the resistor as insulation. Is it possible to add the terminating resistors in the XL or would it be better to make a small box with a DIN plug on one side and a socket on the other ? Hmm, I guess I could put svid and audio sockets in it instead and then just use standard cables. Or mount them in the case even ?

[+bob1200xl]

Seems pretty close... you might try a .01ufd capacitor in series with the 100 ohm resistor. If you are going to mount a separate s-video connector (plus audio) in your case, then you can tweak the values to clean up your signal. (without trashing your composite signals)

 

Bob

 

 

I looked in this thread (thanks to mimo for pointing me at it) and did just this bit:

 

Missing Chroma Output

On the bottom of the board, solder a 100-ohm resistor to the junction of R67 and R68 (the right side in the picture, looking at the top of the board) and put a piece of tape under the resistor to insulate it from the board. Solder a wire from the other end of the resistor to pin 5 of the DIN connector (bottom-left pin from the back).

 

Except I used heat shrink on the resistor as insulation. Is it possible to add the terminating resistors in the XL or would it be better to make a small box with a DIN plug on one side and a socket on the other ? Hmm, I guess I could put svid and audio sockets in it instead and then just use standard cables. Or mount them in the case even ?