130XE - RF box required?

[morelenmir]

As a matter of course I always remove the RF can from my A8 in order to give a little more space on the motherboard. Usually with the 800XL's this has had to be quite a destructive process requiring a Dremel and a diamond wheel. However on the 130XE the thing came off quite easily. However... Once removed the video no longer worked through the monitor port...

 

Is the RF can required on the 130XE? Alternately, I wonder if it is just a case an important line is conducted through the RF circuitry and all that is required is a patch between two or more of the empty pads once the thing is gone?

[flashjazzcat]

I think the RF Modulator produces composite out in the XE line but removing it should have no adverse effect on Y/C video.

[morelenmir]

I think the RF Modulator produces composite out in the XE line but removing it should have no adverse effect on Y/C video.

 

Many thanks FJC!!! I guess that is not the case with the XL's?

 

That would explain why I got a blank screen - my 'Monitor' cable only runs to an yellow composite video plug. Annoyingly my television does not have an SVideo socket, so any more advanced video out would need to go from out from the A8 via the monitor socket and then in through the SCART... That's a bit more work than I was planning on right now.

 

I had planned to set up the Ultimate1MB on two legs via at least one hole located beneath where the RF can has to stay... Frustration.

 

Whereabouts do you locate the U1MB on XE systems?

[+DrVenkman]

 

Many thanks FJC!!! I guess that is not the case with the XL's?

 

That would explain why I got a blank screen - my 'Monitor' cable only runs to an yellow composite video plug. Annoyingly my television does not have an Video socket ...

 

 

 

 

I don't think that's the source of your problem, morelenmir, at least not directly. I can use the same 30+ year old "Monitor" cable (composite + audio) from every Atari machine I've tried it on, from an 800, to my 800XL's, my 1200XL's, and yes, my 130XE.

[morelenmir]

I don't think that's the source of your problem, morelenmir, at least not directly. I can use the same 30+ year old "Monitor" cable (composite + audio) from every Atari machine I've tried it on, from an 800, to my 800XL's, my 1200XL's, and yes, my 130XE.

 

I phrased that poorly DrVenkman, my apologies.

 

What I meant was; that explains why - with the RF can removed - I got no composite video out of the 130XE and hence no picture on my television. With the can back in the display is fine - or at least as fine as its going to get with the RAM interference, but that is another thread!!!

[+DrVenkman]

Ah, what we have here is a terminology issue: you say "RF can" and I think "RF shield," especially since you've been talking about that elsewhere. You mean the actual RF Modulator - got it.

[morelenmir]

Ah, what we have here is a terminology issue: you say "RF can" and I think "RF shield," especially since you've been talking about that elsewhere. You mean the actual RF Modulator - got it.

 

Yes indeed - again my apologies!!!

 

I learned my early electronics from my father. He was a Warrant Officer Engineeer or 'Master Technician' as I think they called them for a while for Radar and Gunnery in the RAF on the early jets like the Hunter and Lightning along with the V-Bombers (the Valiant, Vulcan and Victor) when they first came on the scene in the late fifties. He had in turn gone as an apprentice to first Yatesbury and then Cranwell just after the last war, learning what they called a 'trade' back then from chaps who had probably worked alongside Marconi himself. He talked about 'cans' and 'patches' and 'valves' and the like so I picked it up from him and never lost it even when I went to university. I often hear myself speaking at least fifty years out of date; I am a walking anachronism in many ways!!!

[BillC]

You don't need the RF modulator to combine chroma/luma into composite, just a capacitor. A problem is that when the capacitor is connected it can cause interference between the chroma/luma signals. One way to overcome this is to install a switch that disconnects the capacitor from the circuit when composite output isn't being used, another is to build the capacitor into a dedicated composite only video cable or adapter.

 

Designed by Tomi Engdahl
First published in Internet at 1999, last updated at 2006

This simple adapter can be used to convert Y/C video (S-video) to a composite video. This adapter is useful in cases where your video output device has only S-video output but your signal source accepts only composite video input. This circuit works with both PAL and NTSC video standards.

Y-ground------------------+                          +---------- RCA/composite groundC-ground------------------+Y-------------------------+                          +--------- RCA/composite videoC------------||-----------+            470pF

This circuit can be quite easily build inside a the S-video connector case if a physically small size 470 pF (ceramic) capacitor is used. Larger capacitor values will also work, but cause picture to become "softer". The voltage rating of capacitor can be 10V or more.

This circuit works in practice quite well even though the circuit operation is not ideal. This means that impedances and signal levels not matched exactly right, but near enough to work accetably. The picture quality you get from this circuit is is good, but not as good as with best possible composite video output circuitry.

 

http://www.epanorama.net/circuits/svideo2cvideo.html

[Beeblebrox]

Necrobump

 

Bit of mystery. A 130XE with no rf modulator installed (so of course not expecting composite out). However having read this and other threads I was expecting s-vdeo to work. It doesn't. (BTW the Din5 to s-video cable itself has been ruled out as the issue as works with other A8's.) 

 

So I wondered what needs checking to ensure the connections on the PCB are still in place for S-video in the absence of the RF modulator. 

 

I don't wish to build a dedicated cable for composite. Nor to I wish to reinstate an rf modulator. I just want to run S-video again on this 130XE. 

 

Edit BTW I am not able to get to it to take photos of the PCB just yet. 

I will be checking the chroma and luma lines are connecting to the pins on the Din5 but just wanting to know if I need to check anything else obviously on the PCB itself. 

 

Thanks

Edited January 30, 2023 by Beeblebrox

[Beeblebrox]

Just to add I get no signal on LCD and on CRT I get a black screen with intermittant colour lines flashing up every now and then.

These CRT images from the other day, (again with a known working Din5 to S-video (Hercules workshop) cable):

 

    

 

What I completely forgot to mention is that the RF modulator was removed as part of the Sophia (1st version with DVI) install. But as I understand it the removal of the RF modulator for such an install does not disable S-video so that should still work from the Din5 jack.

 

Any ideas?

[Peri Noid]

It looks partly like a broken Antic to me. You mentioned Sophia - I hope, it's been removed here. RF is not needed if you use S-Video.

[Beeblebrox]

14 minutes ago, Peri Noid said:

It looks partly like a broken Antic to me. You mentioned Sophia - I hope, it's been removed here. RF is not needed if you use S-Video.

Hi. So Sophia works fine. It appears there is just no S-video connection inside the machine or something has been removed during the Sophia install related to S-video.

 

The images above are just when you have din5 to S-video cable plugged in. (Antic is still present, as is Sophia)

 

I'll check the schematics and have a look at the PCB when I can get to it but in the interrim I just wondered if anyone could point me to perhaps an existing post relating to where the S-video might be failing in this case so I can fix it/resetablish the connection, etc.

 

The machine is fine on Sophia but I always like to have at least one other legacy video connection present, and there is no reason why this shouldn't work on this machine, despite Sophia being present.

 

 

 

 

Edited January 30, 2023 by Beeblebrox

[_The Doctor__]

I hate to say this, but I've had to do this when stumped. Returning to fully working stock and then reinstalling upgrades is a path I sometimes had to take. It was quicker than dealing with too many variables from this or that. If it continues to vex you might consider that simplification helpful and then you more than likely will know where things have gone wrong either at base or during re install.

[+scorpio_ny]

3 hours ago, _The Doctor__ said:

I hate to say this, but I've had to do this when stumped. Returning to fully working stock and then reinstalling upgrades is a path I sometimes had to take. 

My goto 800XL had stopped working one day with a blank screen.  It had a Sophia installed and it would not give me any normal clues to what was going on. I replaced the Sophia with GTIA again I was able to get the normal red screen of death to begin my trouble shooting.

These enhancements to the Atari computers are great. But when issues occur,  they really throw off the established troubleshooting methods due to change in behavior introduced by the new hardware. 

 

[Beeblebrox]

Thanks all.

 

I actually worked it out half hour ago.

 

Turns out it was the oscillator crystal and one transistor located under the Freddie chip bottom left of the PCB. Replaced the transistor after taking it's reading off the board that didn't seem right, and then it transpired the oscillator wasn't working. Replaced both and got S-video alongside DVI out. For once not a painful long drawn out fix.  Bit of a fluke fix tbh.

 

I had both outputs hooked up simultaneously on my LCD and CRTs: left hooked to Sophia DVI LCD, and right hooked up to S-video Din5 on CRT: