Do I need a UAV to fix this ?

[Ricky Spanish]

Stock 1200XL / 20" JVC CRT tv Video in (colour-luminace to a Y-connector). Happens with some programs, others are perfectly fine. Thanks !

 

Edited August 16, 2022 by Ricky Spanish
my grammar sucks.

[+Stephen]

Odd - you shouldn't be seeing the artifacting (orange / blue) using separate luma/chroma (s-video).  Are you sure you're not feeding composite into the chroma input?  OH - you say you are using a Y connector.  If this means you are using composite input, then no - a UAV won't fix it.  You will always get artifacting in hi-res mode if using RF or composite.  Only s-video will not, but then, you get dotted white lines, not solid.

[Ricky Spanish]

40 minutes ago, Stephen said:

 but then, you get dotted white lines, not solid.

Translation ? Cause I'm not a video expert.

[Rybags]

It's NTSC artifacting caused by the hires video signal being interpreted as colour information when using RF or composite video input.

 

You need to use S-video.

2 problems though - some devices actually combine it into composite which will still produce artifacting, and S-video is pretty dead as a standard and not included on TVs these days.

[flashjazzcat]

1200XL video is a mess until it's fixed up. I recommend Bob Wooley's mod, which I routinely perform on all 1200XLs which come through my hands:

 

http://retrobits.net/atari/clearpic.shtml

 

Edited August 16, 2022 by flashjazzcat

[ACML]

1 hour ago, flashjazzcat said:

1200XL video is a mess until it's fixed up. I recommend Bob Wooley's mod, which I routinely perform on all 1200XLs which come through my hands:

 

http://retrobits.net/atari/clearpic.shtml

 

I've done this mod on all my 1200XLs and it is a great improvement besides returning Chroma to the monitor jack.  I do have a question.  I've used both the 8-bit Classics and Hercules s-video cables and I still get mild jailbars.  Does the ClearPic2002 mod combine composite and chroma somewhere.  My guess is not, not my area of expertise, but since you are just swapping components and not adding any new traces, how could it?  Any idea why I'd still get mild jail bars using ClearPic2002?

 

I say, no new traces save the added wire from the motherboard to the chroma pin on the monitor jack (junction of R27 and C61 to J2-5).  Is this really the best point to pick off chroma or is there a better place to grab it if this location shares a path with composite which might be the source of the jailbars?

 

   

Edited August 16, 2022 by ACML
spelling

[flashjazzcat]

2 minutes ago, ACML said:

Does the ClearPic2002 mod combine composite and chroma somewhere.

I assume it preserves composite video out, so chroma and luma will have to be mixed somewhere. Jailbars are usually on the luma signal, however, and not a result of chroma/luma mixing. I installed UAV in a 1200XL a couple of years back and was disappointed that jailbars remained (in fact, were worse than with the legacy video circuit) and could not be alleviated via cable shielding, etc. Supposedly, jailbars are caused or worsened as a side-effect of DRAM refresh (which causes voltage fluctuations in the video circuit, or AC interference; someone else can explain this better than I), but even then, there have been users still suffering from jailbar effects even on machines in which the DRAMs have been removed and the base memory replaced by SRAM. It's a complex and subtle problem.

[ACML]

31 minutes ago, flashjazzcat said:

I assume it preserves composite video out, so chroma and luma will have to be mixed somewhere. Jailbars are usually on the luma signal, however, and not a result of chroma/luma mixing. I installed UAV in a 1200XL a couple of years back and was disappointed that jailbars remained (in fact, were worse than with the legacy video circuit) and could not be alleviated via cable shielding, etc. Supposedly, jailbars are caused or worsened as a side-effect of DRAM refresh (which causes voltage fluctuations in the video circuit, or AC interference; someone else can explain this better than I), but even then, there have been users still suffering from jailbar effects even on machines in which the DRAMs have been removed and the base memory replaced by SRAM. It's a complex and subtle problem.

Thanks for the explanation.  I've read threads that blame jailbars solely on cable shielding.  For the 1200XL, the ClearPic2002 is awesome and only costs like $3 in parts.  It only replaces existing components so the mod still appears a "stock-like" look.  How on earth Atari engineers either intentionally left out chroma or just missed it before the mainboard went into massive production baffles me.    

[flashjazzcat]

2 minutes ago, ACML said:

How on earth Atari engineers either intentionally left out chroma or just missed it before the mainboard went into massive production baffles me.

I still have this idea that it was to allow compatibility with Commodore video cables, but I'm probably wrong.

[+mytek]

14 hours ago, flashjazzcat said:

Jailbars are usually on the luma signal, however, and not a result of chroma/luma mixing. I installed UAV in a 1200XL a couple of years back and was disappointed that jailbars remained (in fact, were worse than with the legacy video circuit) and could not be alleviated via cable shielding, etc. Supposedly, jailbars are caused or worsened as a side-effect of DRAM refresh (which causes voltage fluctuations in the video circuit, or AC interference; someone else can explain this better than I), but even then, there have been users still suffering from jailbar effects even on machines in which the DRAMs have been removed and the base memory replaced by SRAM. It's a complex and subtle problem.

Sorry you experienced jail bars after your UAV install.

 

For future reference here's what I did...

 

I have a 1200XL with a UAV installed and still got jail bars until I changed to a cable with individually shielded wires like the one made by Hercules Workshop, only mine was a DIY version I built from a high quality double shielded Mini-DIN S-Video cable and a DIN-5 plug. Once I changed the cable, the picture had zero jail bars via the S-Video output (separate Chroma and Luma connections). The previous cable I was using that had jail bars was made by 8-Bit Classics.

 

Here's what my installation looked like in the 1200XL (please ignore some of the other unrelated upgrades that I installed later).

The ground strap noted as 'GND BRIDGE' in the image is required when the RF modulator has been removed, otherwise you will see some video interface, which I believe looked a bit like a moving herring bone pattern if my memory serves me correctly. I used a piece of copper solder wick for the strap, but a simple piece of wire is all that is required.

 

I did nothing fancy on the UAV end, and let it pick up its GND and +5V from the CD4050 socket it was plugged into. Over time this setup got tested with both the original linear 5V regulators and later with upgraded switching regulators (hence the reason the heat sink is missing - it's no longer needed). In both cases I never experienced any video noise issues.

 

BTW, this unit still had the stock 64K DRAM in use in the beginning, and now has a 256K Rambo XL upgrade. Still DRAM in both cases, and no jail bars in either case.

 

Edit: I'll have to see if I have a photo of the underneath side to show specifically where the Chroma wire was connected to (Check out this article and scroll down the page to find the photo of where the Chroma connects to on the A/V jack).

 

Edit2: I also found during my tests of the UAV that the composite video output initially was noisy until I installed that ground strap where the RF Modulator had previously been.

 

Edit3: Jail bars really are caused by the Chroma signal somehow mixing with the Luma signal. It can happen in several ways. One is by cross coupling of the signals when using non-individually shielded wires in the A/V connection cable between the computer and your TV/Monitor. The other is electronically induced by direct coupling of the two signals in the video driver circuit of the Atari computer, hence the reason people have also experienced good results by breaking this interconnecting circuit (usually a capacitor that is being used to cross connect the Chroma to the Luma to create a composite output). Of course by breaking this connection, you end up with a B&W image coming out the composite connection, so people also install a switch to reconnect the broken circuit for when color composite output is desired. Basically anytime Chroma gets into your Luma connection the end result will be jail bars when viewed with an S-Video monitor.

 

[Ricky Spanish]

6 hours ago, flashjazzcat said:

I recommend Bob Wooley's mod

Will that work with my setup ? Thanks.

[flashjazzcat]

5 minutes ago, Ricky Spanish said:

Will that work with my setup ? Thanks.

A stock 1200XL? Certainly.

[Ricky Spanish]

Just now, flashjazzcat said:

A stock 1200XL? Certainly.

Awesome. Thank you.

[+bob1200xl]

I have some opinions on this, but no real verification.

 

Shielded cable probably has a lot more capacitive load than twisted pair. This will limit bandwidth to the TV, which will likely smoosh any jailbars.

 

Don't connect LUMA to CHROMA to get COMPOSITE. The cable already has COMPOSITE. You can drive CHROMA from COMPOSITE if you have not

done the "fixes".

 

I think you can cure jailbars by leaving C60 in the board.

 

Jailbars seem to be caused by ground bounce when the DRAMs execute REFRESH. REFRESH occurs even if you install SRAM because ANTIC can't see the SRAM.

 

Ricky: I did all my mods to your 1200XL. Get a new video cable and try adding C60 (100nf). Do not modify the new video cable, OK?

 

Not picking on anybody, here...

 

Bob

[Ricky Spanish]

1 hour ago, bob1200xl said:

Ricky: I did all my mods to your 1200XL. Get a new video cable and try adding C60 (100nf). Do not modify the new video cable, OK?

Will do ! Thanks Bob !

[ACML]

2 hours ago, bob1200xl said:

Get a new video cable and try adding C60 (100nf).

 

Bob

The original C60 is listed as a 100pf axial ceramic (25V).  Are you saying replace it now with a 100nf to reduce jailbars?

 

Would these work?

https://www.amazon.com/mxuteuk-Multilayer-Monolithic-Capacitor-0-1uf-104/dp/B08B3VCK42/ref=cm_cr_arp_d_product_top?ie=UTF8

Edited August 18, 2022 by ACML

[+mytek]

I didn't want to side track this topic any more than I already have, so I decided to start a separate topic talking about what causes 'Jail Bars'.

 

 

[+bob1200xl]

Nope... 100pf is what you want.  (where did I get xxxnf?)

 

I believe it would be marked 102.

 

Bob

 

 

 

 

[ACML]

Just checked for parts.  I believe a 100pf is usually marked 101.  A 102 is a 1nf.

 

 

Edited August 19, 2022 by ACML

[Ricky Spanish]

Ok I just ordered the Hercules cable. One down. Now to order the 100pf capacitor. 

[ACML]

My order from Amazon for the 100pf caps arrives Monday.  I'll be busy, but for some reason I may be up at 11:30 PM firing up the solder iron. 

 

If this works, I will be very pleased.  Regardless, it at least provides me one more opportunity to break something by accident.  The law of averages has to caught up at some point.  Fingers crossed.

 

Engineer's moto:  If it ain't broke, it needs more features.

 

Then there's the other side of the sword, "Perfection is the enemy of good enough".  It takes a while and more than a few "been there done that" moments to arrive at the latter.

 

 

[Ricky Spanish]

40 minutes ago, ACML said:

If this works

For the problem I posted ?

[ACML]

2 hours ago, Ricky Spanish said:

For the problem I posted ?

Reducing or getting rid of jailbars.  

[Ricky Spanish]

16 hours ago, ACML said:

Reducing or getting rid of jailbars.  

Ahhh I see, but I don't have a jail bar problem. I though that was why Bob recommended getting a new cable & using the 100Pf capacitor on c60 for my specific problem. 

Edited August 21, 2022 by Ricky Spanish
grammar sucks ha-ha

[Ricky Spanish]

No jail bar problem. Just colour bleed problem. So hence I'm following Bob's advice.

Hard to take a good pic of a CRT tv screen.

Edited August 21, 2022 by Ricky Spanish
added information