Investgating PAL 7800 picture issues (was 7800 RGB Musings)

[+karri]

Not RGB scart. I use pins 15 and 20. So there should be a monochrome image at least.

 

But now I powered up my scope. I can see the sync signal on the LMO pin going to pin 15 in the SCART. But the CRO has pretty random signal going to pin 20.

 

The grounds go to pins 4 and 17.

 

But perhaps I have messed up something on the TV?

 

PS. I just solder random wires to the SCART connector at this point. I still don't have a real cable...

 

PPS. I may have the LMO and CRO going to the wrong pins. Swapping them now...

[+karri]

Now I have a really sharp and steady Asteroids game running - in monochrome  

Obviously this TV does not support S-video...

[juansolo]

Are you connected to the composite pin as @marauder666 suggested or is this wired as S? If it's wired as S have a twiddle of the 7800 chroma trimmer (top one on the main board), just to make sure it's not that.

[marauder666]

Chroma always looks pretty random, but if you zoom right in you can see the colourburst.

 

You could temporarily connect the CVO on the board to the composite on the TV.  Should get colour, but will look a little weird, like its got fake scanlines!  We have no idea why this is happening.  Doesn't using same FMS6400 and a 2600.

 

 

 

 

 

[+karri]

Thanks for the ideas. In the long run I want to have correct colours. For eJagfest in two weeks I can live with monochrome or even striped composite. At least I should be able to demo my experiments on the SN cart.

[+karri]

I connected the CVO and got really nice colours on the screen.

 

But I see the point with crawling pixels.

For Wizzy this small living is definitely not a problem. Actally it gives a nice breeze to the scenery.

 

This is so much better than the RF-screen I have been using so far. I may actually add a composite, a s-video and a 3.5mm audio output. Then I can choose what to use.

[marauder666]

On a 2600 composite modded console we use a 3.5mm stereo socket for composite and mono audio.  Tip connected to composite.

Makes a neater install.  Most TVs with stereo audio input, will recognise when audio is input into the left channel only and automatically send it to the right channel too.

Edited October 5, 2023 by marauder666

[+karri]

I still need to finish the installation. But I am really happy to have an usable PAL 7800 unit. Thanks guys!

[+karri]

4 minutes ago, marauder666 said:

On a 2600 composite modded console we use a 3.5mm stereo socket for composite and mono audio.  Tip connected to composite.

Makes a neater install.  Most TVs with stereo audio input, will recognise when audio is input into the left channel only and automatically send it to the right channel too.

A neat idea, but I believe I will be using headphones while developing. So most likely I add an extra connector for the composite video out.

[juansolo]

Glad it's working right. The Composite out is there but sometimes gets an odd scanline effect for some reason we haven't fathomed yet. We use the FMS6400 all over the place and it's never done that before. If it works, it's no problem to use it. You will need to set the colours but you should be able to do that via composite ok. When you get an S-Video capable TV that'll just be a lot better.

[+karri]

The space is quite small so I decided to add 3 pins only for the composite. GND - Composite - GND. Then it does not matter which way I insert the cable. Here is the 3D printout. The hole to the left is for an 3.5mm Audio. The hole to the right is for S-video. The square cutout at the bottom is for Composite video.

7800PAL.stl

[+karri]

Unfortunately this design was too tight. I gave up and cut away some plastic.

7800PAL.stl

[juansolo]

As long as the plugs go in I call it a win.

[+-^CrossBow^-]

2 hours ago, karri said:

Unfortunately this design was too tight. I gave up and cut away some plastic.

7800PAL.stl 20.39 kB · 0 downloads

And that is one of the more brittle case shells discussed earlier in another thread. Again, I can tell by the rectangular shape around the original RF opening where the plastic is different textured and out of place from the rest of the shell. So not sure what you used to cut it but you did good!

 

[+karri]

10 minutes ago, -^CrossBow^- said:

So not sure what you used to cut it but you did good!

Solder gun to melt exactly what I want and a file to clean up the cuts. Note: the Composite video out has to be in the most left position as there happens to be a cut in the lower shell at the position for the connector to go when you lift the pcb.

[+karri]

I realized that my better TV does not even have SCART anymore. So I bought a cheap €36 anything to HDMI converter. It arrived today.

 

I picked up the instruction leaflet. It was in broken Swedish? Here is a translation:

 

"Dry your hair to remove excess moisture. Detach the cable and plug it into the mains socket. Push the On/Off switch to adjust the air speed for you hair" ???

 

I was a bit scared to plug in my 7800 to the unit after this. Reading the box text revealed that there may be some guy in India who has a Swedish/Gibberish lexicon for making the box and the manuals.

 

But to my very big surprise the 7800 is now connected to my TV using HDMI.

 

[marauder666]

@karri  get it connected by svideo.

[+karri]

5 hours ago, marauder666 said:

@karri  get it connected by svideo.

Soon. I am waiting for my S-video cable to arrive. These cables are not stocked anywhere.

[+karri]

I did get my S-video cable and the colours are less washed out compared to the composite colours.

 

Is there some calibration paper of how to set up the trimmers on board and on the S-video board? My desire is to show the same colours as defined by the a7800 emulator. Like a PAL warm would match the real PAL 7800 colours.

 

Composite output:

 

S-video output:

 

Both images are then converted to HDMI as my TV does not have S-video or SCART connectors.

[juansolo]

It's difficult because there's no utlity for PAL like there is for NTSC and if you use the NTSC one it'll be wrong... Top trimmer on the 7800 main board for this one. Tweak it while it's running. Also do it slow if you're going through a processor/coverter, some can be a little slow when it comes to dealing with the chroma signal changing when it comes to catching up.

 

We set it up based on Ballblazer and Commando on the 7800 side, Combat on the 2600 side. But that's mainly because we know how they look when it's 'right' But for adjustment I recommend starting with my proceedure in the instructions. Basically start a human vs human game of Ballblazer. Get it so you have both spinners on screen as we do in the pics. Hit pause. The top spinner should be red-brown (more red). If you move to the outside of the playfield, out of bounds should be burgundy. When you start the game the Lucasfilm logo should be on a dark brown background and the gradients in the lettering should be even.

 

Next move on to Command. The title screen is a worst case scenario of dark greens which the PAL 7800 doesn't like doing (colour rolling in the darker greens is usually noticable here, that's just the Maria being the Maria, nothing you can do about that). The flesh of the soldier should be brown. Start the game, the background should be brown and green. We usually use this to tweak the settings after we've got them somewhere close with Ballblazer.

 

Obv from this point just tweak to taste.

 

On the 2600 side we use Combat (bottom trimmer on the 7800 main board). Select game 2, hit start. Background again should be dark green, the playfield surround and obsticles should be a sandy yellow. Left tank light blue, right tank pink. That'll get you somewhere near.

[Trebor]

19 hours ago, karri said:

Like a PAL warm would match the real PAL 7800 colours.

If it helps, from feedback received, and posts elsewhere, PAL Hot is typical what I've seen many people choose concerning what they experience from their PAL 7800 console.

 

From the calibration via CPS Diagnostic Cart for the NTSC units, factory tuning (cool palette) typically take place early on from the system being powered up (Diagnostic/Calibration screen appears in 10 seconds).  Ultimately, the palette leans towards warm, or for many (or 'most' from what I've seen) hot, after 15-20+ minutes of consistent console runtime. 

 

Nonetheless, warm provides a nice compromise, in part, when there is neither emulator or FPGA simulator that mimics the 'warm-up' factor of Atari console palettes.

 

Also, here is the Color Bars Selector Demo with a header set specific for PAL, along with just a no header binary file:

Color Bars Selector Demo (1984) (PAL) (D98BC2F8).a78Color Bars Selector Demo (1984) (D98BC2F8).bin

 

A few corresponding PAL charts for reference are in the spoiler below, and information is available about ensuring brightness level for the display is proper set.

Spoiler

 

 

 

[juansolo]

Another one done. @zeropolis79's PAL 7800. Nice board this one, so the installation side was easy enough and it has a cracking picture. Sadly the Post Office decided to do a number on the case and that's gonna need some significant repairs. Just waiting for some more epoxy to land to finish that up.

Just a reminder, these old machine's plastics are quite brittle to start off with, package them as if the courier/postal service is going to play football with it whenever you post them.

Edited November 2, 2023 by juansolo