800XLF S-video C54 removal alternative to eliminate jailbars,etc on LCD screens

[Beeblebrox]

Regarding S-video Jailbars/zigzag/checkerboard interference when using LCD screens  - I've recently implemented the well known C54 capacitor removal mod on a stock 800XL. (Well actually I installed a switch which means I get to keep composite/RF as I can toggle the C54 on and off).

Worked really well. See here.

 

I realised I have the same issue on my 800XLF (800XL with a Freddie chip for those who aren't familiar).

 

I therefore planned to do the same but realised I can't find the C54 cap on my 800XLF's PCB. Is there an equivilant to the C54 which when taken out of the circuit does the same? 

They layout of the XLF PCB is quite different from stock 800XLs.

 

Thanks

 

 

Edited April 1, 2022 by Beeblebrox

[BillC]

27 minutes ago, Beeblebrox said:

I therefore planned to do the same but realised I can't find the C54 cap on my 800XLF's PCB. Is there an equivilant to the C54 which when taken out of the circuit does the same? 

They layout of the XLF PCB is quite different from stock 800XLs.

I searched the forum and found the post linked below which may help.

 

 

[ACML]

What is the equivalent capacitor or resistor on the 1200XL main board to lift?  I assume that will also remove the jail bars (i.e. no composite signal crossing over into the monitor cord if its open downstream of the monitor jack).  

[reifsnyderb]

This may help to find the capacitor equivalent to c54.  Here is a schematic of the video section of an 800xl with chroma added:

You'll need a schematic and you'll be looking for the capacitor that connects the composite video (between what here is C54 and R56) connection to the chroma section (between R67 and R68).

 

In this schematic you can see how Lumina and Chroma are combined for the composite video.

 

 

Edited April 2, 2022 by reifsnyderb

[Beeblebrox]

7 hours ago, ACML said:

What is the equivalent capacitor or resistor on the 1200XL main board to lift?  I assume that will also remove the jail bars (i.e. no composite signal crossing over into the monitor cord if its open downstream of the monitor jack).  

That was gonna be my next post question too 

[Beeblebrox]

@BillC @reifsnyderb  thanks for your suggestions/info - I'll have a look at these sometime this weekend.

[reifsnyderb]

I found I have 2 1200XL schematics with the video.  Here they are:
 

1200XL OEM video.pdf

 

1200XL Schematics.pdf

 

If these schematics are right, the 1200XL is missing the chroma output on pin 5, too.  (I don't have a 1200XL to look....)

 

So, I'd try adding the chroma line at the junction of Q7 and R45 and removing C63.  The chroma line should go to pin 5 on the monitor port and have a 100 ohm resistor between the pin and the junction of Q7 and R45.

 

 

 

 

Edited April 2, 2022 by reifsnyderb

[Beeblebrox]

Well bit of an update regarding the 800XLF and also the 1200XL - having installed the CV switches in both thus ridding S-video of the cross talk causing the jailbars/zigzags/checkerboard interference on an LCD monitor.

 

800XLF

 

Thanks @BillC @reifsnyderb - The signposted old topic thread and the diagram putme on the right track.

 

After a painful 3 hours of staring at 800XLF scematics, images of PCBs and my own XLF PCB, and jabbing away at it with my multimeter following various video circuit paths, I finally found C46!  The differences between component placement and number between different revisions of XLF boards (those made in April  1984 and September 1984 - mine being the latter), made it really difficult. Doesn't help my understanding of schematics isn't the best.

 

The capacitor that connects to the composite circult (C46), was hiding to the left of the RF modulator unit.

 

So I made up my detachable header cable and hooked it up to one ofmy newly purchased 2 position swtiches:

 

          

 

.... and whilst there is a tiny amount of vertical banding when composite is disconnected on S-video, the difference with the crosstalk removed is very obvious and a great improvement as expected:

 

Before (with C46 and crosstalk from composite):

 

    after with C46 switched off, no signal crosstalk: 

 

       Concealed switch in one of the casing vents:    

 

 

1200XL

 

This wasn't without issues and still isn't right at all when it comes to hooking up the chroma. I may well do the Supervideo 2.1XL mod at some stage as I hear it takes advantage of an extra colour circuit element the 1200XL has which other XLs don't have.

 

It was as (@reifsnyderb)  stated:

 

Adding the chroma line at the junction of Q7 and R45 and removing C63, where rather than removing C63 I just lifted the right side off the PCB and installed the swtich cable as before:

 

The chroma line was connected to pin 5 on the monitor port with the 100 ohm resistor between the pin and the junction of Q7 and R45, at the lower leg of Q7 as that is the only connection that gave me a passable colour signal

(I'd tried the left side of R186 and also left of R44 but colour was poor):

 

 

Incidentally you'll notice there is a wire already connected to the left side of R44. This connects up Chroma to the bespoke mini DIN S-video that this modded 1200XL came with when I bought it.

 

It could be that someone has already applied a video mod such as Clearpic or Super Video to this 1200XL. I've not checked to see as yet.

 

However whislt I have Chroma colour hooked up now on the original DIN, it is definitely not right and there is lots of bleeding and over blooming/saturation when the S-video on LCD is used. To make matters worse the image off the mini S-video port is even worse now on LCD. The mini S-video din isn't really usuable now on LCD displays with this current issue.

 

By contrast CRT isn't too bad. Not great but no where near as bad as the LCD.

 

Incidentally this has nothing to do with the fact this 1200XL currently has the NTSC chipset. There was no bleeding of colours or anything aside the jailbars/zigzags/checkerboard patterns on LCD before I undertook this mod. Nor is it the LCD screen as proved by the other 800XL/XLF working well with it after the CV switch mods is installed.

 

The little switch works and eliminates the jailbars, etc crosstalk when C63 is turned off - it's just the colours that are looking awful now.

 

I forgot to take some pics of the screen when it was hooked up so will do so at some stage.

 

In the meantime the little switch glued in place in the 1200XL's casing vent:

      

 

 

So I am gonna put this on hold whilst I fiz a few other A8s (including a 600XL recently saved from landfill I suspect).

Edited April 4, 2022 by Beeblebrox

[reifsnyderb]

Looking more at the 1200XL schematic, I'd also remove (or lift a leg of) C61 as that goes to the RF Modulator.

[Beeblebrox]

@reifsnyderb thanks for the suggestion. So in addition to the C63 switch installed over the weekend, I also just lifted the right (top) side of C61 and installed a switch cable for this too, (see pics below)

 

Appears to not have made any notable difference unfortunately when I flick the switch enabling or dissabling C61. Running an LCD display off the stock DIN to S-video connection no difference, on bespoke mini din a little shift vertically as you flip the switch but still same poor image. This is all the while always having C63 disabled.

 

Basically on the stock DIN to S-video (with chroma), is still the same over saturated output with some vertical bleeding and what I believe is called ghosting. The bespoke mini din output is uttertly horrendous with little colour and horrendous vertical bleeding.

 

So I think this is more likely an issue I have taking the chroma to pin 5 of the stock Din and where 

 

I think I am gonna look to see if any prior owner had undertaken the clearpic mods or Supervideo 2.1XL one or any other at the point they installed the mini S-video din. Likely I'll do the latter Supervid mod.

 

********

 

Some pics re C61:

 

         

 

(Following images are all with C63 and C61 disabled BTW.)

 

Here is the stock Din to S-video on LCD (with recently hooked up Chroma to pin 5), showing some bleeding and ghosting:

  

   

 

 

and here is the output from the bespoke 4pin S-video mini Din on LCD, (again with C63 and C61 disabled), showing horrendous vertical banding and colour bleeding plus lack of colour:

 

        

 

So something definitely not right as this mini din output wasn't like this before I did these mods and hooked up the Chroma to the Stock DIN. #

 

Weirder still - even if I remove the Stock DIN pin 5 to Chroma hook up line, the mini din poor output remains the same. So perhaps something has happened elsewhere, or perhaps a grounding issue? Very odd.

 

BTW for visual ref, stock DIN on left, bespoke mini 4 pin S-video on right with 3 x wires attached to it, one picking up chroma from the left side of R44 which was done by whomever installed the mini din.

All wiring continuity checks out with all the detachable header connectors.

 

       

Edited April 5, 2022 by Beeblebrox

[Beeblebrox]

Just a quick thought. The 20guage wiring for the 2 x new CV switches is thin, unsheilded and quite long. Furthermoore as per the images said cabling also rests on the PCB and across several ICs. Is there a possibility the wiring is picking up noise from the PCB and ICs causing some of the colour bleeding/bad output? I don't think it could cause such a horrendous issue as is evident with the mini DIN output - but worth asking.

 

I might try routing them around to avoifd the ICs when I can get to it.

[reifsnyderb]

I suppose it's possible.  For a test, eliminate the wiring (and switches) and see what happens.

[_The Doctor__]

also the last picture shows insulation melted in and contaminating your solder joint

[Beeblebrox]

I pressed pause in the 1200XL troubleshooting last spring. Must get back to it. I've learn a fair amount fixing other models of A8 since so perhaps I'll get to the bottom of it. 

[+Stephen]

Looks like someone is trying to win an award for most threads necro-bumped in a week!  Why stop at just 10 month old ones?

[_The Doctor__]

Since the last couple years have been unkind, and I've had to deal with loved one and pets passing away, I am getting to all of the stuff that is in my unread thread list that does not show resolution. If it's been shelved, I am going to see if it can be handled, helped, or if it's been resolved the thread will show it and will have a closure of the issue. Looks like a good deal of things are now getting back into gear and we'll be happier for those projects coming off the back burners. More software and more working Atari's the better! More Atari computer users the better! Hopefully with a few more jumping in and support of the vendors it's going to be a better next couple of years.

[flashjazzcat]

Having lost both my parents and one cat in the space of the past eighteen months (and the cat died two days after my dad passed away), I really do sympathise (as I did on mIRC the other night when we talked about this) and can appreciate all too well how real life can interfere with one's involvement with the forum. The stated intention to patrol the forum and resolve or offer closure on subjects which have lain neglected for months or years on end is certainly admirable. However, the following threads were bumped to the top of the feed in a manner which didn't appear to offer closure, extra information, or otherwise drive the discussion forward:

 

https://forums.atariage.com/topic/334215-bloody-planet-alien-breed-inspired-game/page/2/#comment-5204053

https://forums.atariage.com/topic/336808-atari-8-bit-meet-up-saturday-june-25th/#comment-5203719

https://forums.atariage.com/topic/332724-starflight-1986-pc-development-started-on-the-atari-800-originally/#comment-5206062

https://forums.atariage.com/topic/334408-800xl-with-purple-and-green-wires/page/2/#comment-5203344

https://forums.atariage.com/topic/333581-lucasfilm-press-conference-pass/#comment-5206744

https://forums.atariage.com/topic/334049-atari-800xl-keyboard-keeps-typing-n/#comment-5205122

 

Seven to ten months had elapsed since the last post in all the above threads, and in one case you bump the thread by actually replying to yourself.  I was actually driven to ask admin if any facility existed to curate the forum content in a manner which would keep such bumped threads from the top of my feed, but no-one has so far answered the question. If no reply is forthcoming in ten months, I guess I'll bump the thread.

 

[/end OT]

[_The Doctor__]

A) showing admiration for the box art is something I wanted to do.

B) Amiga and it's items being at Atari events is something I support, if found it funny.

C) The post for the Atari version of the game was truncated and isn't there... I requested it be deleted and it hasn't happened yet.

D) Responded to a thank you I missed.

E) Valkyrie was something I was tracking down and talking to someone about, it was bumped so I'd remember it and maybe catch the attention of another person who was doing the same.

F) Gave a 'your welcome' to a 'thank you',  repeating keypress issue has come up a bit so it serves more than one purpose to show it worked.

 

I like when people say thank you and your welcome, especially when they've been helped or given help. It's nice.

Edited February 11, 2023 by _The Doctor__

[SviRu]

On 4/4/2022 at 7:19 PM, Beeblebrox said:

Well bit of an update regarding the 800XLF and also the 1200XL - having installed the CV switches in both thus ridding S-video of the cross talk causing the jailbars/zigzags/checkerboard interference on an LCD monitor.

 

800XLF

 

Thanks @BillC @reifsnyderb - The signposted old topic thread and the diagram putme on the right track.

 

After a painful 3 hours of staring at 800XLF scematics, images of PCBs and my own XLF PCB, and jabbing away at it with my multimeter following various video circuit paths, I finally found C46!  The differences between component placement and number between different revisions of XLF boards (those made in April  1984 and September 1984 - mine being the latter), made it really difficult. Doesn't help my understanding of schematics isn't the best.

 

The capacitor that connects to the composite circult (C46), was hiding to the left of the RF modulator unit.

 

So I made up my detachable header cable and hooked it up to one ofmy newly purchased 2 position swtiches:

 

          

 

.... and whilst there is a tiny amount of vertical banding when composite is disconnected on S-video, the difference with the crosstalk removed is very obvious and a great improvement as expected:

 

Before (with C46 and crosstalk from composite):

 

    after with C46 switched off, no signal crosstalk: 

 

       Concealed switch in one of the casing vents:    

 

 

1200XL

 

This wasn't without issues and still isn't right at all when it comes to hooking up the chroma. I may well do the Supervideo 2.1XL mod at some stage as I hear it takes advantage of an extra colour circuit element the 1200XL has which other XLs don't have.

 

It was as (@reifsnyderb)  stated:

 

Adding the chroma line at the junction of Q7 and R45 and removing C63, where rather than removing C63 I just lifted the right side off the PCB and installed the swtich cable as before:

 

The chroma line was connected to pin 5 on the monitor port with the 100 ohm resistor between the pin and the junction of Q7 and R45, at the lower leg of Q7 as that is the only connection that gave me a passable colour signal

(I'd tried the left side of R186 and also left of R44 but colour was poor):

 

 

Incidentally you'll notice there is a wire already connected to the left side of R44. This connects up Chroma to the bespoke mini DIN S-video that this modded 1200XL came with when I bought it.

 

It could be that someone has already applied a video mod such as Clearpic or Super Video to this 1200XL. I've not checked to see as yet.

 

However whislt I have Chroma colour hooked up now on the original DIN, it is definitely not right and there is lots of bleeding and over blooming/saturation when the S-video on LCD is used. To make matters worse the image off the mini S-video port is even worse now on LCD. The mini S-video din isn't really usuable now on LCD displays with this current issue.

 

By contrast CRT isn't too bad. Not great but no where near as bad as the LCD.

 

Incidentally this has nothing to do with the fact this 1200XL currently has the NTSC chipset. There was no bleeding of colours or anything aside the jailbars/zigzags/checkerboard patterns on LCD before I undertook this mod. Nor is it the LCD screen as proved by the other 800XL/XLF working well with it after the CV switch mods is installed.

 

The little switch works and eliminates the jailbars, etc crosstalk when C63 is turned off - it's just the colours that are looking awful now.

 

I forgot to take some pics of the screen when it was hooked up so will do so at some stage.

 

In the meantime the little switch glued in place in the 1200XL's casing vent:

      

 

 

So I am gonna put this on hold whilst I fiz a few other A8s (including a 600XL recently saved from landfill I suspect).

Any other 800XLF mods to further fix video output? Removed C46 > big difference but still there is some color bleeding. Looking for mods that might fix that issue also.

[Beeblebrox]

5 minutes ago, SviRu said:

Any other 800XLF mods to further fix video output? Removed C46 > big difference but still there is some color bleeding. Looking for mods that might fix that issue also.

A decent S-video cable. Whatever you do, if you are running on an AV composite cable you'll have some form of bleeding/artifacting.

 

There are various other mods which involve tweaking passive components, like the following, (this one for stock 800XL's, so would be different for the XLF:

 

 

[SviRu]

11 minutes ago, Beeblebrox said:

A decent S-video cable. Whatever you do, if you are running on an AV composite cable you'll have some form of bleeding/artifacting.

 

There are various other mods which involve tweaking passive components, like the following, (this one for stock 800XL's, so would be different for the XLF:

 

 

OFC I use quality SVIDEO cable. My A8 has zero color bleeding compared to modded C46 800XLF. I know 800XL is worse but was looking for additional mods that could be done. VBXE is the last resort. 

[Beeblebrox]

33 minutes ago, SviRu said:

My A8 has zero color bleeding

which model just out of interest?

 

Well there are of course UGV and UAV, Spectre AV as well. I've installed a good few UGVs as very cheap and nice output:

 

 

It may or may not have a bearing, but remember an 800XLF is effectively an XE, (it has a Freddie and maybe it is closer to the XE in terms of video output quality. The XE range is never that great stock). Although the PCB quality of the 800XLF is undoubtidly better than the XE PCBs.

 

BTW it might be worth checking the video circuit components, (the transistors), and also the R38 colour pot. Spray the latter with contact cleaner and give it a couple of turns.

 

I am not expert here BTW.

 

Personally installing a UGV or SpectreAV is cheap and easily obtained.

Edited January 29 by Beeblebrox