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Remove rf modulator


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#1 Marius OFFLINE  

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Posted Fri Mar 4, 2011 1:43 AM

Hi

I want to remove the rf modulator. Can I simply remove it or do I have to restore som contacts on the atari pcb then?

It's an atari xe

Thanks
M.

#2 flashjazzcat OFFLINE  

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Posted Fri Mar 4, 2011 3:11 AM

As long as you don't want composite video, just pull that hunk of metal out. IIRC, the XE modulator generates the composite video signal "in house", so you'll lose that when the RF is removed.
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#3 papa_november OFFLINE  

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Posted Mon Feb 11, 2013 2:07 AM

I really want to get rid of the RF modulator can on my 130XE, but I want to keep composite video just in case. Apparently, all you have to do to get composite from S-video is to stick a 470pF capacitor in line with the Chrominance signal and join it to the Luminance signal. I could easily do this at the connector for the RF modulator right on the motherboard, but before I do it, I'd like to know if this is going to degrade the performance of the S-Video signal. I suppose I could always put a switch in if it does.

What would be best is if I could replicate what is happening inside the RF modulator, but I don't think there's any schematics for it floating around.

#4 atari8warez OFFLINE  

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Posted Mon Feb 11, 2013 5:26 AM

I really want to get rid of the RF modulator can on my 130XE, but I want to keep composite video just in case. Apparently, all you have to do to get composite from S-video is to stick a 470pF capacitor in line with the Chrominance signal and join it to the Luminance signal. I could easily do this at the connector for the RF modulator right on the motherboard, but before I do it, I'd like to know if this is going to degrade the performance of the S-Video signal. I suppose I could always put a switch in if it does.

What would be best is if I could replicate what is happening inside the RF modulator, but I don't think there's any schematics for it floating around.


Combining the signals (with the capacitor) does not affect the S-Video signal performance.

I just did this on a 600XL. Removed the RF modulator, installed a 5 pin DIN monitor connector, connected the luminance and chrominance signals to the DIN connector to obtain S-Video, and combined them (with a 470 pf caps) to obtain composite. The S-Video mod I did on the 600XL also required a 75 ohm resistor (to reduce banding on LCD screens somewhat) on the chroma line, but that resistor apparently needs to be disconnected for Composite usage, so I also added a switch to do that.

#5 BillC OFFLINE  

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Posted Tue Feb 12, 2013 10:42 AM

Combining the signals (with the capacitor) does not affect the S-Video signal performance.

I just did this on a 600XL. Removed the RF modulator, installed a 5 pin DIN monitor connector, connected the luminance and chrominance signals to the DIN connector to obtain S-Video, and combined them (with a 470 pf caps) to obtain composite. The S-Video mod I did on the 600XL also required a 75 ohm resistor (to reduce banding on LCD screens somewhat) on the chroma line, but that resistor apparently needs to be disconnected for Composite usage, so I also added a switch to do that.

The 130XE uses a different RF modulator which also contains the circuitry to create the composite video signal, on the XL series the RF modulator just creates the RF signal.

#6 BillC OFFLINE  

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Posted Tue Feb 12, 2013 10:50 AM

I really want to get rid of the RF modulator can on my 130XE, but I want to keep composite video just in case. Apparently, all you have to do to get composite from S-video is to stick a 470pF capacitor in line with the Chrominance signal and join it to the Luminance signal. I could easily do this at the connector for the RF modulator right on the motherboard, but before I do it, I'd like to know if this is going to degrade the performance of the S-Video signal. I suppose I could always put a switch in if it does.

What would be best is if I could replicate what is happening inside the RF modulator, but I don't think there's any schematics for it floating around.

Attached is a Sobola schematic of an RF modualtor that is supposed to be for the XE.
Attached File  XE-CO70000-NTSC-modulator.pdf   8.52KB   150 downloads

#7 atari8warez OFFLINE  

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Posted Tue Feb 12, 2013 5:14 PM

The 130XE uses a different RF modulator which also contains the circuitry to create the composite video signal, on the XL series the RF modulator just creates the RF signal.


Yes they look different too, so does that mean if one removes the RF modulator from an XE there is no way to obtain Chroma and Luma signals any more, or do they simply loose the "built-in" composite output? If the latter is true then one can re-create the composite from Luma/Chroma.

#8 pixelmischief OFFLINE  

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Posted Tue Feb 12, 2013 5:34 PM

I removed the RF can from my 130XE and the S-Video still worked fine.

#9 Larry OFFLINE  

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Posted Tue Feb 12, 2013 6:28 PM

I started to remove the RF mod. from my NTSC 130XE. When I cut the 2nd or 3rd connection, I lost most of the video. I'm merely suggesting that you don't do anything that is not reversible until you make sure that it works. In my case, it was easy enough to solder that connection back together and then everything worked fine again. I did not merely lose composite, I lost most all of the video.

Check this thread and pics.

http://www.atariage...._hl__+modulator

-Larry

#10 atari8warez OFFLINE  

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Posted Wed Feb 13, 2013 1:51 AM

I removed the RF can from my 130XE and the S-Video still worked fine.


So that means the Composite can be restored by simply combining luminance with chrominance + 470 ohm ceramic cap just like i did in my 600XL.

#11 Marius OFFLINE  

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Posted Wed Feb 13, 2013 11:54 AM

So that means the Composite can be restored by simply combining luminance with chrominance + 470 ohm ceramic cap just like i did in my 600XL.


I guess you mean 470pF right? and how do i connect that? chrominance to one leg of the cap and luminance to the other leg of the cap? or else? please let me know!
thanks

M

#12 Creature XL OFFLINE  

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Posted Wed Feb 13, 2013 12:56 PM

http://de.wikipedia....=20051006154953

Maybe this?
Even I was able to make it. Although not for the A8. But should be the same.


#13 atari8warez OFFLINE  

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Posted Wed Feb 13, 2013 6:03 PM

I guess you mean 470pF right? and how do i connect that? chrominance to one leg of the cap and luminance to the other leg of the cap? or else? please let me know!
thanks

M


Ooops, yes you're right, meant to say pF, and yes that's basically it.

You connect the chroma signal to one leg and the line coming from the other leg combines with the Luma on it's way to the Composite pin of the 5 pin DIN connector. There is no Luma trap in the circuitry so color artifacts are not removed.

The photo shows how I did it in my 600XL. It's a variation of kjmann's s-video upgrade, it uses the DIN connector instead of an s-video connector for all signals including the audio, and the upgrade is not on a separate board. I used some of the vacant video circuitry vias and traces on the motherboard to route the upgrade. I am not hugely impressed with the quality of the image on my LCD screen, on CRT it looks better without any visible vertical banding but banding is apparently a problem with some LCD displays. But for such a simple/inexpensive upgrade, I think it's worth the effort, certainly much better than having to connect my 600XL to a TV next to my desk :)

Attached Thumbnails

  • svideo upgrade (3).jpg
  • svideo upgrade (4-Small).jpg
  • svideo upgrade (5-Small).jpg

Edited by atari8warez, Wed Feb 13, 2013 6:37 PM.


#14 atari8warez OFFLINE  

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Posted Thu Feb 14, 2013 12:43 AM

Further to the above. Here are two videos showing the effects of the 75 Ohm resistor on Composite video.





#15 atari8warez OFFLINE  

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Posted Fri Feb 15, 2013 12:45 AM

http://de.wikipedia....=20051006154953

Maybe this?
Even I was able to make it. Although not for the A8. But should be the same.


Yes, that's exactly it.

#16 SS OFFLINE  

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Posted Wed Apr 17, 2019 3:48 PM

As long as you don't want composite video, just pull that hunk of metal out.



BUMP!

I just put a SOPHIA board into my 600XL. Everything seems to be working fine with it so I want to remove the RF modulator to make some more room inside the case. I also figure that I can reporpose the RF hole on the back of the case to run my 3.5mm audio plug out of.

How exactly do I go about pulling the modulator out? Is it actually soldered to the board? Do I need to desolder it from the underside in order to remove it? Thanks for any insight.

#17 Gunstar OFFLINE  

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Posted Wed Apr 17, 2019 4:06 PM

I believe FlashJazzcat has a video that shows exactly what to do. Yes, LOTS of solder to remove. On an 800XL I'm rebuilding, I didn't bother to remove the RF box, because it is a hassle, and instead I just gutted the electronic board out of it, and left the box in place with the RCA plug that I will wire composite video too. There's another thread on here someplace where I think I posted a picture of it...I busted it up into tiny pieces with a wire cutter, screw driver and needle nose pliers in order to gut it.


Edited by Gunstar, Wed Apr 17, 2019 4:10 PM.

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#18 flashjazzcat OFFLINE  

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Posted Wed Apr 17, 2019 4:21 PM

Use a large soldering iron tip with high thermal mass. Any one of my videos covering VBXE installation is likely to touch upon RF modulator removal.
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#19 DrVenkman OFFLINE  

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Posted Wed Apr 17, 2019 7:18 PM

Use a large soldering iron tip with high thermal mass. Any one of my videos covering VBXE installation is likely to touch upon RF modulator removal.

 

Exactly. I followed one of Jon's videos but the trick, such as it is, is to use the largest tip you have and just heat the crap out of those solder lugs, slowly working a small flat-blade screwdriver under the edge of the modulator can once the solder around the lugs gets soft enough to let you do it. Then just keep heating the lugs, using the screwdriver to gently work the can up and out of the board mounting holes. 

 

I've now done this on several different vintage Ataris. Some models have a single solder lug close to the edge of the PCB, one on either side about halfway back along the can length, and one on the back side of the can parallel to the first. Other models might have four lugs - two on each side space along the length of the can from front to back. In any case, start with the lug or lugs closest to the edge of the board until you can get the screwdriver between the can and board and take your time. There's a lot of thermal mass and the can housing itself will get fairly warm as you work, but that just means it'll take a few minutes to do it.



#20 SS OFFLINE  

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Posted Wed Apr 17, 2019 8:37 PM

One more question.  Can I still use the wires that run to the RF modulator once the modulator is removed?  I need to pull audio from the board to run to a 3.5mm audio jack.  Wire #2 seems the most convenient place to get it or is there a better point on the board to use?  Also is wire #1 (x) a grounding point or is there a better spot for this too?  Thanks again for any info; I am so close to finally getting my problematic 600XL project up and running.

 

rf modulator.jpg






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