Horizonal white lines across picture, but only when using RGB Scart - Repost with new video link

[WilboDC]

Hi All

 

Sorry for the repost, but I realised the last video I tried to attached was in a format that could not be displayed easily, so here goes again....

 

I have a strange issue with my Jag which I am struggling with and could do with some advice please.

 

It's a recently acquired unit purchased from eBay. I'm on my 3rd round of "wish I hadn't sold it all, must buy retro gear back again"!

 

Jag plays absolutely fine when using RF output, picture is as good as it should be on RF with no lines at all.

 

When using an RGB Scart lead I'm getting horizontal white lines flickering across the screen. This happens on multiple carts, and on multiple TV's, and I have now tried multiple Scart leads.

The frequency of the lines seems to change depending on what is being displayed at the time. There's always a lot on the intro screen, but the number reduces whilst playing a title (but never go away completely)

 

A video showing what's going on is here: 

 

At the same time as purchasing the lead I bought a complete cap replacement set. Fitting this has made no difference. The lines were there before the recap, and exactly the same after. I even replaced the caps individually testing the Jag each time to see if I had fixed the problem, or made it worse.

 

Any advice much appreciated!

 

Cheers
Wilbo

[+Stephen Moss]

Well although not impossible, I would think it unlikely that the RF converter and modulator could mask such issue if they were a fundamental artefact of the primary video single generated by Tom.

 

Therefore, although you have tried multiple SCART leads if they were all made by the same company/person? If so then it is possible that all have the same inherent fault that could be the source of the problem, however if they were produced by different people then although not impossible it would seem less unlikely that the SCART lead may be the issue.

 

So, if we feel that we can eliminate Tom, the SCART lead and the TV (as you have tried several) as the possible cause what does that leave us with? Well, not much apart from an issue with the single leaving Tom, not being correctly transferred to the AV connector, so personally I would be looking L6, L7, L8, L10 through L18 and R83.

For the ferrites you could try pushing on them with something non conductive with the Jaguar running to see if the image improves because there is a bad solder joint or just apply a little more solder, the same can be done for R83 or you could measure the voltage across C49, C50 or at TP 30 which I would expect to read approximately 9V DC if there is not issue with R83.

Although I am doubtful that an R83/C49/C50 would result in the issue shown, I would check it any way just to be sure.

 

If that appears to provide no solution and you have not already done so try using the forums search facility to search both the Jaguar and the Hardware forums as I have a feeling this or something very similar has come up before and so the solution may already be posted somewhere on AA.     

[str0m]

Something as simple as a mucky port on the jag? Clean the contacts up or try pulling the lead back out 1mm or so

[Zerosquare]

This is a very strange fault. Single-pixel gaps are visible in the lines:

which strongly implies the problem is in the digital signal generation part. But then, if it was, it would show up on RF as well!

 

Also, the lines are white/grey, so it can't be anything specific to one of R/G/B outputs.

 

As other have said above, I'd recommend cleaning the A/V port and the cable, and trying a different cable if you have one. Maybe there's some kind of weird contact issue or short-circuit inside the cable.

[WilboDC]

Hey Guys

Thanks for all the advice, much appreciated! Here is where I'm at so far...

Was away for a few days after posting for help so thought I'd fire up the Jag yesterday afternoon and start running through your suggestions. To my surprise it started up perfectly with no lines on the screen at all. Played games for a bit with no issues and thought it may have been down to a bad connection that I'd sorted in moving the console about. However, after time the lines started to appear, only very occasionally though. I left the machine on for a while and the problem slowly got worse and back to it's original state as per the video. I'm wondering if the unit got cold whilst I was away?

I've tried two scart leads from different suppliers now with the exact same results, although they are both what I would call budget leads, nothing like the very chunky official Atari lead I used to have.

The connectors at the back of the Jag have been cleaned with IPA and are nice and shiny. I've also tried the connector pulled out a bit from the back.

 

I've pushed gently on the ferrites and R83 with no visible difference. R83 checks out perfect with a multimeter.

 

Voltage at C49/C50 reads at 8.1V DC. Not sure if that's too low? I also have no components on the PCB at C48 & C50 - is this normal?

My next move is to try to apply a bit more solder to all the ferrites & R83 in case there is a bad connection there.

 

Any more suggestions most appreciated, will keep you all updated. The fact I've seen this run perfectly now makes me even more determined to fix it!

Cheers
Wilbo

[Zerosquare]

Since the issue appears to be intermittent, I wonder if it's really correlated to the type of video cable, or if it's just a coincidence.

Can you connect both the RF cable and the SCART lead to your TV, and switch back and forth between the two inputs when the problem occurs?

 

 

[+Stephen Moss]

10 hours ago, WilboDC said:

Voltage at C49/C50 reads at 8.1V DC. Not sure if that's too low? I also have no components on the PCB at C48 & C50 - is this normal?

If I remember I will compare it to a Jag I have, although I doubt it is critical.

The only use I can think of for that output would be for the TV to automatically switch to the SCART input which is think generally should be around 12V input anyway and if that is what it is for there is no guarantee that it was wired in to any of your  SCART cables.

If that is what it was provided for then I could be wrong but don't I think problem with that would produce what you are seeing. 

 

10 hours ago, WilboDC said:

However, after time the lines started to appear, only very occasionally though. I left the machine on for a while and the problem slowly got worse and back to it's original state as per the video. I'm wondering if the unit got cold whilst I was away?

That does sound more like a bad joint issue, as the Jag is used it warms up and thermal expansion interferes with a joint, or a component start overheating and creating issues.

If it is a bad joint then unfortunately it will be difficult to find, with no idea where problem lies the only real solution is to wait for the problem to occur and start pushing down on the solder joints/parts of the PCB and see if anything changes, if it does that at least narrows down you search area.

Start at the rear left quadrant as that is where most of the video circuitry is located.

[WilboDC]

Thanks again for all the help guys!

 

This is where I'm at currently.

I cut the end off a Phono to Phono cable and temporary hooked it directly to the input side of the Composite Video and Video Ground ferrites.

 

I've captured a video of the Jag running through RGB scart, RF, Composite, and back to RGB Scart for you to see what happens. My view is that RF and Composite are as good as can be expected with no lines.

 

 

I took apart one of the RGB scart leads I purchased and the manufacturing quality left a lot to be desired! Next stage is to rebuild the TV end of dismantled scart lead to a standard I'm happy with, and connect direct to input side of ferrites to confirm signal is good there. If it is and I still have an issue with Jag AV connector back on the cable I'll reflow all connections to AV out.

 

Cheers!
Wilbo

 

 

[WilboDC]

Hi All

 

Latest update on the White lines saga.

 

So, I made good the scart end and made connections directly to the input side of the video/audio output ferrites and still had the same problem.

 

Then I had the idea of trying the Jag on a CRT TV, and the results are different, and hopefully something that someone has seen before.

 

Instead of the broken white lines I see on an LCD, on a CRT the picture seems to shift aspect ratio between 4:3 and Widescreen. Not in a constant pattern, just random, like the lines used to appear.

I've tried this on both a Toshiba and Sony Trinitron and get the same on both TV's. Some kind of sync signal issue?

Does this shed any light on what the source of the issue could be? I'm going to do some reading up on Scart signals as its been a long, long time, but if anyone has any ideas they would be much appreciated

Cheers!
Wilbo

 

 

 

[WilboDC]

Last update - Disconnecting Pin 8 in the scart end has temporarily sorted the problem!

 

Found the following online and can only assume that the voltage being output by the Jag is fluctuating enough to keep switching the signal between 16:9 and 4:3

This was clearly visible on a CRT, but for some reason my LCDs were just showing those strange white lines.

 

*0 V–2 V means no signal, or internal bypass
*4.5 V–7 V (nominal 6 V) means a widescreen (16:9) signal
*9.5 V–12 V (nominal 12 V) means a normal (4:3) signal

 

Now need to trace down what is being supplied to and coming out of R83. But for the moment, I can cope with manual switching knowing that I'm getting full picture quality.

 

However, seeing the Jag running through a Sony Trinitron CRT has made me realise how amazing the quality of CRTs were again!

 

Cheers!
Wilbo

 

 

Edited January 23, 2023 by WilboDC

[str0m]

Not an expert so could be wrong but is it maybe swapping between PAL and NTSC as it isn't increasing the width, just the height is shrinking and NTSC is less vertical resolution so will show black bars on a PAL TV. Didn't realise the Jag could actually do widescreen unless that info you post above is just a generic scart pin details?

 

Sounds like you are making progress anyway, Cybermorph is waiting for you lol

 

EDIT as I type this......my memory has been jogged, I had a similar issue with a Dreamcast via RGB Scart which boiled down to the Pico PSU I had put in not having 12v on it. DC originally uses 12V for the optical drive but I had a gdemu in it which doesn't require is so most remove the 12v rail or swap the psu to avoid heat. With the 12v missing my old TV would either not display the DC at all or it was incredibly dark. Put the original PSU back in with 12v and it worked perfectly so I would say this does confirm what you have said that for you it is a fluctuating 12v signal

Reading my emails back with the ebay psu seller, I also had zero issues when using the DC on RF with that pico psu

[Zerosquare]

@WilboDC: looks like your video cables are miswired. Pin 8 on the SCART side is normally connected to pin 11A on the Jaguar side, which supplies ~9 V DC, which should work fine.

 

Anyways, that's interesting. I'd never had guessed that it could cause those weird lines.