+2a double vision - uncommon problem

sliderules · November 2013

Helloo - I was helped by Guesser on a previous occasion on a toastrack, so many thanks to him for that!
Today's problem is the RGB display from a +2a - mono output comes with excessive ghosting/double vision:-o which is not conducive for programming!

I can't see a way to upload photos here! I originally went on the RWAP forum where I've got some advice and ideas but was told the problem is uncommon and to try here too. This link will take you, kind reader, to the pics I uploaded there and comments I got there:

http://rwapadventures.com/forums/viewtopic.php?f=5&t=77&p=209#p209

I'd be grateful for any advice on how to deal with this !

all the best!
Jeff

guesser · November 2013

Could be that the signal levels are too high into the TV?

skagon · November 2013

I still haven't understood how you connected the +2 to the TV. In the other thread, you mention "I've tried different scarts - no probs with toastrack or spec issue 2 48k - just the amstrad". How did you test a SCART with a 48k? Which SCART? Where?
For the record, the toastrack and the grey +2 are slightly different in their outputs, so a SCART cable made for the toastrack isn't necessarily going to work on a +2. The internal resistors are different and also the +2 incorporates the BRIGHT signal on the RGB, where the toastrack does not.
However, it does look like ghosting from too high signal levels, like the mate upstairs said.

sliderules · November 2013

Hi Guesser
interesting idea! I don't know is the answer! But I can add this to my growing list of things to look at! cheers

sliderules · November 2013

Hello skagon - thank you for looking at all that - most appreciated! OK right I've not been as clear as I might:
toastrack goes into same TV as the +2 - but with a toastrack dedicated scart cable - no problems at all, very crisp mono
the +2 I've used several different allegedly +2 dedicated cables, each of which gives the double vision on same tv as I use with toastrack. Both +2 and toastrack are also fine with CRT
the 48k does everything asked of it perfectly - I think I was maybe just celebrating it, but no I don't plug it into the flatscreen. But am thinking about a conversion.
Thank you again! any ideas v welcome!

1024MAK · November 2013

Which +2 is this?
Is it the grey +2 that uses a power plug similar to a 48K?
Or is it a black +2A or +2B that uses a DIN plug for the power connector?
I ask, because the +2 Grey uses a different SCART lead to that used on a black +2A or +2B.

Can you please confirm that the picture from the UHF TV out is okay and shows no artifacts like on the pictures you uploaded to RWAP's forum.

Looking at the pictures that were posted on the other forum, there are artifacts on the colour picture, they are just not so noticeable.
On the black and white picture, if you look carefully you can see a thin weak line ahead of (to the left) of a thicker, darker line. This is most unusual. I would say that it is a digital timing error, not any type of analogue error. It cannot be signal reflections or incorrect termination in the TV.

You cannot upload pictures/images or attachments to this forum, as this is not permitted. To show pictures on this forum, you have to upload them to a photo sharing web site, your own web site or another web site which allows photos and images to be shared. Then to show the image, use the tool button above the edit box (looks like yellow and black postcard, but I think it is suppose to be a mountain range) to link to a URL of the image that you uploaded on the other web site.

Mark

1024MAK · November 2013

sliderules wrote: »

OK right I've not been as clear as I might:
toastrack goes into same TV as the +2 - but with a toastrack dedicated scart cable - no problems at all, very crisp mono
the +2 I've used several different allegedly +2 dedicated cables, each of which gives the double vision on same tv as I use with toastrack. Both +2 and toastrack are also fine with CRT
the 48k does everything asked of it perfectly - I think I was maybe just celebrating it, but no I don't plug it into the flatscreen.

Okay, here you talk about a CRT TV and a flat-screen TV.

Is this problem only occurring when using a SCART cable on your +2/+2A/+2B to a LCD flat-screen TV?

Does it work okay when using a SCART cable on your +2/+2A/+2B to a CRT TV?

Mark

1024MAK · November 2013

"prolog wrote:

On WoS there is a whole Science of Scart going on and controversy over the loading on pin 16 etc. - the more mathematical posters there (that have cranked ohm/resistance/voltage calculations) seem to think there shouldn't be significant ULA overheat problems using the rgb/scart; the man with the thermometer on his ULA says otherwise.

So, I am now going into panic mode about the appropriate scart lead to use with my toastrack - please tell me there's a safe option!! Couldn't see anything on sellmyretro

Don't worry about SCART leads killing you Spectrum, the heating effect that is being talked about takes about one hour or more to show up. For short periods of testing this is not a problem. Also, so far, only one person has reported the problem. I'm not saying there is no problem, just that these SCART leads have been on sale for some time. So no need to panic.

Mark

sliderules · November 2013

Mark, Hi, I think we've met before somewhere !? I recognise the mak1024 moniker from somewhere. Thanks for looking at this...

Yes! it says its a black +2a with din power brick etc. and yes

your ideas about crt:
it is fine rf to crt - but I've just now tried it a SCART to a CRT and I get the weird result as here (I just typed the alphabet and I get white Klingon letters on the black screen):

http://rwapadventures.com/forums/viewtopic.php?f=5&t=77&p=212#p212

I didn't believe it when I saw it - great idea, but weirder than before!
Jeff

sliderules · November 2013

Thanks for the upload advice, I'll look into finding out where my photobucket site is
J

DaRkHoRaCe · November 2013

Hey hoo! I need a +2A scart cable ready to use. Where I should buy one?
Not the cheaper one please :D
I'd like something with resistant connectors and good video quality.
If someone could make one from scratch I can buy it.

Edit: at reasonable price of course :D

1024MAK · November 2013

It looks to me like there is an incompatibility between the +2A, the RGB to SCART lead and your TV's.

I suspect the TV's are switching between RGB mode and composite video mode.

Do either of your TV's have menu or settings to be manually set to RGB mode?
If yes, try this :D

Mark

1024MAK · November 2013

sliderules wrote: »

Mark, Hi, I think we've met before somewhere !? I recognise the mak1024 moniker from somewhere.

I use the same ID on eBay and on a number of forums: ATARI-Forum, StarDot, Sinclair ZX World, Memorum, QL FORUM to name a few ;-)

Mark

sliderules · November 2013

Hi again
so the final picture is here which is exactly the same +2a going to CRT via RF and the output is exactly what one would like!

http://rwapadventures.com/forums/viewtopic.php?f=5&t=77&p=213#p213

Mystery! Your thoughts would be very gratifying!

In sum: we have a black +2a with din power supply

RF out to CRT - FINE!!
RGB to SCART - Flatscreen - white screen ghosting on black letters and on games any mono image is ghosted, but colour stuff good
RGB to SCART - CRT - black screen with white Klingon alphabet

How weird is that?
Jeff

sliderules · November 2013

1024MAK wrote: »

It looks to me like there is an incompatibility between the +2A, the RGB to SCART lead and your TV's.

I suspect the TV's are switching between RGB mode and composite video mode.

Do either of your TV's have menu or settings to be manually set to RGB mode?
If yes, try this :D

Mark

:-o Thanks Mark. Interesting. Initially I thought it was the lead, I have a couple from different companies but same results. The Flatscreen has no probs with RGBcomp from my toastrack, so I don't see why my tellies would be confused by the Amstrad and not the Sinclair, but I'm listening to what you're saying. I'll have a look through their settings, but normally they just detect and flash up AV/Scart before kicking into the computer's signal. But I'll go and have a play just now!
J

sliderules · November 2013

DaRkHoRaCe wrote: »

Hey hoo! I need a +2A scart cable ready to use. Where I should buy one?
Not the cheaper one please :D
I'd like something with resistant connectors and good video quality.
If someone could make one from scratch I can buy it.

Edit: at reasonable price of course :D

I got the one I'm using now off RetroComputerShack on ebay.

1024MAK · November 2013

RGB to SCART cables...

See also here and here (and if you search, many other threads :D )...

Mark

skagon · November 2013

sliderules wrote: »

The Flatscreen has no probs with RGBcomp from my toastrack, so I don't see why my tellies would be confused by the Amstrad and not the Sinclair...

...because, like we've been telling you all along, the signals are different. The toastrack is TTL RGB through 68Ω, the grey +2 is TTL RGB through 75Ω but with integrated BRIGHT and the black +2A/B or +3 are TTL RGB through 150Ω. The CSync signals are TTL (68Ω), TTL (75Ω) and 1.2V p-p (470Ω and 150Ω pull-down), respectively.
So, while a cable for the toastrack *might* work on the grey +2 and definitely the reverse, it most definitely will not work on a black +2A/B or +3. The Sync signal will be too low -- which is probably why the old CRT can't understand colour and proper sync, while the newer LCD TV with its digital input is only ghosting, again probably due to the interaction of a low sync signal and a digital comb filter.

sliderules · November 2013

Yes yes skagon! I've taken all that on board! I use different cables for the different machines - the toastrack has its own scart cable and I don't use that with the +2a. I have 3 cables from different sources for the latter, all sold as for the black amstrad, but same effect on each :(

+2a double vision - uncommon problem

Comments