ClearPic2002 worked great, but no NTSC RF video

[ACML]

I completed the ClearPic2002 mod on my 1200XL and the results were fantastic. The fuzzy stock video is sharp using an S-Video (separate chroma and luma) and composite. I checked the NTSC RF modulated (Channel 3) and no video. Should the ClearPic2002 mod render RF video inoperative? If not, what component/s in the mod would be most directly related to the RF modulated video? Thanks!

[+Guitarman]

I may be wrong, but I think doing the Clearpic mod renders the RF unusable. This is why some remove the RF modulator altogether from the board and use the space to add an s-video plug.

[+bob1200xl]

ClearPic disconnects the RF modulator. Try restoring R22 and R27. No promises, but those are required for RF.

 

Bob

 

 

 

I completed the ClearPic2002 mod on my 1200XL and the results were fantastic. The fuzzy stock video is sharp using an S-Video (separate chroma and luma) and composite. I checked the NTSC RF modulated (Channel 3) and no video. Should the ClearPic2002 mod render RF video inoperative? If not, what component/s in the mod would be most directly related to the RF modulated video? Thanks!

[ACML]

ClearPic disconnects the RF modulator. Try restoring R22 and R27. No promises, but those are required for RF.

 

Bob

 

Bob,

 

Thanks for the quick reply. Would replacing R22 and/or R27 effect the ClearPic2002 mod? I love the sharpness and the quality and don't want to compromise the results. Also, if I replace them (R22 & R27), I don't remember their original values. What Ohm resistance do I replace them with. I can't imagine needing the RF modulated output, but if it does not effect the ClearPic2002 output for S-Video or composite, I don't think there's any harm in keeping the capability. You never know, maybe my monitor cable will break and then its RF to the rescue. If RF is restored, should it also be cleaner and sharper?

 

Thanks Bob!

Edited June 21, 2011 by ACML

[+bob1200xl]

R27 is 3.0K and R22 is 4.3K. I don't know that restoring them will affect the video. The RF itself may be affected... You'll just have to try it.

 

Bob

[ACML]

R27 is 3.0K and R22 is 4.3K. I don't know that restoring them will affect the video. The RF itself may be affected... You'll just have to try it.

 

Bob

Update: I completed another Clearpic 2002 on a 1200XL, but this time I left R22 and R27 in place to see if RF video was retained and if so, did it effect the quality of the chroma and luma. Well, looks like R22 and R27 are absolutely for RF and when connected, it did not adversely affect the quality of the chroma and luma signals. However, the RF was of so very poor quality, its nothing you'd consider keeping. That being the case, I removed R22 and R27 like Bob's instructions list. Wow, I have two 1200XLs and the sharpness is a little different, but I used different sources for resistor and capacitor components. Maybe there is some machine to machine variances, but both look great.

 

I used:

1/4 watt carbon film resistors (5% tolerance)

50V, 5% tolerance capacitors

0 ohm resistors (1/4 watt, one black stripe)

 

This modification is significantly better than just replacing L15 and C115 with a 1 ohm resistor. If you want to use Onmiview 80, the Clearpic 2002 mod featured in retrobits.net is a must!

 

P.S. Another plus for using the Omniview XE OS is that its allows 64K on an OS based on the 400/800 OS-B and it has the fast math routines. It runs the AHL Benchmark in half the time of the stock Atari OS. Also runs Archimedes Spiral much faster.

Edited August 9, 2014 by ACML