Supervideo Atari 600xl - PAL

[shoestring]

I want to share my results & findings doing this simple mod. Anyone here who has performed the Supervideo mod using the original article by Ben Poehland would have quickly discovered a mistake regarding the position of the CV disable switch, although it doesn't take much investigation to realize that the toggle switch is meant to be installed at L12 ( see 600xl schematics ) it's still somewhat confusing. Installing the switch at L13 as suggested actually breaks the RF out which you don't want, so I put the choke back in. I hope this helps someone clear up some confusion regarding the position of the CV toggle switch.

 

He mentions L14 for the installation of the 2.2ohm resistor but I didn't notice any improvement or change so I re-installed the 820uh inductor. Maybe I'll hook up a toggle switch temporarily and toggle between the 2.2ohm resistor and inductor to determine if it's worth installing the resistor instead.

 

I also couldn't see any improvement or degradation of the luma/chroma display when toggling the CV switch so i couldn't justify drilling a hole in the back of the 600XL since I might not be using it much, Instead I left the switch inside the case and mounted it on top of the rf shield with the switch set to CV on. I'm tempted to re-install the rfc and not have a switch since I don't think there's any benefit but If anyone knows better then please let me know.

 

Here is a small summary of the standard changes I made.

 

1.Cut the ground connection between pin 2 & 5 on the foil side of J7

2.I removed C109 - this small change has the most impact

3.Replaced R123 ( 390 ohms with 75 ohms )

4.Restored luma ( via 75 ohms ) and chroma ( via 100 ohms ) to J7

 

The other challenge was making a cable to go from the back of the Atari to the Commodore monitor. I had the incorrect orientation, so white.. which I designated as audio was wired to pin 1 ( luminance ) instead of pin 3 on the Atari end. Stupid I know.

 

I'm quite happy with the results, RF isn't too bad, it's probably the best I've seen on any 8bit after doing these changes.

 

 

 

 

[ndary]

can you upload pictures from the changed you made on the PCB?

[shoestring]

Sure. I'll get get in there some time this week or on the weekend and update the thread.

[shoestring]

can you upload pictures from the changed you made on the PCB?

 

 

See attached. I hope that helps.

 

I realized that I used the wrong valued resistor at L14 ( 2.2kohms instead of 2.2ohm ), so I removed the choke and installed the 2.2ohm.

 

There appears to be a little improvement so I'm leaving the new resistor in.

Edited February 25, 2016 by shoestring