Sync issue on Enterprise 128

[JohnFante]

Hi

I am having a problem displaying a demo program on my Enterprise 128 retro computer that I have connected via RGB-Scart to my OSSC (running latest firmware).

I have made two adjustment in the default settings:

Sync opt.
Analog sync LPF = off

Output opt.
240p/288p proc = Line3x: Linetripled 720p output.

That has cured most of my issues and the picture is normally rock solid. However I now have a rather strange issue left.

I am trying to run a demo that looks like this (video taken of scart output directly to tv): Demo-scart.

When I try to run that through my OSCC (that gives me much better picture quality) I get this on the display: Sync error.

Any suggestions to what I can change in the settings to get it to catch that?

[BuckoA51]

Analogue sync LPF off is highly unusual. Without knowing exactly what the demo is doing it’s hard to say. Demo software often does highly unusual things/tricks to push hardware beyond it’s usual limitations.

[JohnFante]

Thank you for the reply! I have so far had best result with “Analog sync LPF = off”. If it is “on” the picture – in some cases – have a tendency to turn on an off. It is like the OSSC can not fix the sync.

This particular demo is not a huge thing for me but I would like to have the most stabile overall setup. Are there some settings that are common to adjust for 8 bit machines in the Spectrum, Amstrad, MSX “area”? I know that no machines are the same but maybe there “common” issues?

No matter what thank you for your help 🙂

[BuckoA51]

Do you know what kind of sync the computer uses? Composite video, clean CSYNC, etc?

[JohnFante]

I think it is csync but I am not sure. The video RGB out from the machine looks like this:

Video out – Enterprise 128

The scart end needs some small resistors. This is the normal pinout:

Scart resistors

My cable should have all the necessary resistors etc.

[BuckoA51]

So it looks like we have csync and composite sync available from the machine, question is, does your cable have the correct attenuation on the sync line? It is extremely strange to have analogue sync lpf off entirely with 15khz sources.

[nmalinoski]

So it looks like we have csync and composite sync available from the machine

I think you mean “csync and sync-on-composite”; csync is composite sync.

[JohnFante]

does your cable have the correct attenuation on the sync line

I should have. I am using this cable from Retrocables. I have opened the scart end a bit and there are resistors in there. It is used by a “lot” of people in the Enterprise community … lot in quotation marks, we are not that many 🙂

It is extremely strange to have analogue sync lpf off entirely with 15khz sources.

I have not done a lot of testing of the different OSSC settings so it can be that it is the wrong thing I have turned off. I turned Analog sync LPF off because it said on the wiki that “Required if there is noise or glitches on the sync line.” and I was having issues with some games loosing picture. The screen just turned black once in a while. Turning this off made it better but it can be the wrong solution to my problem.

[paulb_nl]

Standard sync settings to try are setting H-PLL Pre-Coast and Post-Coast to 3 and tweaking Analog sync Vth. Keep Analog sync LPF at default 2.5Mhz.

Can you post some pictures of the resistors in the cable? The drawing you posted of the SCART pinout has only 100 Ohm resistors which are not enough.

[JohnFante]

Standard sync settings to try are setting H-PLL Pre-Coast and Post-Coast to 3 and tweaking Analog sync Vth. Keep Analog sync LPF at default 2.5Mhz.

Ok 🙂 I will start testing …

Can you post some pictures of the resistors in the cable? The drawing you posted of the SCART pinout has only 100 Ohm resistors which are not enough

The scart end is glued together but I wrote the company that produces the cable and they got back very quickly:

“The resistors value are 100ohm(in RGB signals and Sync) and 470 ohm between pin 8 and 16 for RGB activation singnal.”

[paulb_nl]

According to the video out specs the sync is TTL level and the RGB signals are 4 volts. The 100 Ohm resistors are not enough. They should be at least 330 Ohm for RGB. For TTL Csync 470 Ohm is usually used. Otherwise the sync voltage will be too high for SCART and may damage the OSSC.

The 470 Ohm which is already in your SCART cable is not used for Csync but for the RGB activation signal which is only for some devices like SCART TV’s. The OSSC does not use it.

You should be seeing a very bright image with your current cable.

At this page you can also see that they recommend to replace the resistors with 330 Ohm if the image is too bright which seems to confirm it. http://www.ep128.hu/Ep_Konyv/EnterFace.htm

[JohnFante]

You should be seeing a very bright image with your current cable.

I do not when I use the OSSC. If I take the scart directly to my TV/monitor (an old Samsung that has both scart and DVI and VGA) then the picture is rather bright.

Therefore, the resistors could very well be to small. There are reports of people using 220R resistors with good result. I will give that a go and see if that changes things :-).

[JohnFante]

I am waiting for a new RGB-cable with a 220 ohm resistors instead of the 100 ohm to see if that solves my sync problem.

In the meantime I am looking for advice on getting the OSSC to show a interlaced picture correctly.

The image is this loading screen. When I run the program the picture turns on and off like this.

I have talked to the author of the program and he writes this about the picture:

“It is an interlace LPT:

40 lines upper border
6×9 lines are 6 4color character lines (Bricky text)
100 lines are attribute mode
6×9 lines are 6 4color character lines (Prise text)
28 lines between Prise text and Enterprise text
8 lines Enterprise text
2 lines color lines
sync: 14+3+4+1+4
40+54+100+54+28+8+2+26=312
Sync (there is no reload bit in this sync
F2 92 3F 00 00 00 00 00 00 00 00 00 00 00 00 00
FD 00 3F 00 00 00 00 00 00 00 00 00 00 00 00 00
FC 00 20 3F 00 00 00 00 00 00 00 00 00 00 00 00
FF 00 3F 38 00 00 00 00 00 00 00 00 00 00 00 00
FC 12 06 3F 00 00 00 00 00 00 00 00 00 00 00 00
LPT continuing
40 lines upper border
6×9 lines are 6 4color character lines (Bricky text)
100 lines are attribute mode
6×9 lines are 6 4color character lines (Prise text)
28 lines between Prise text and Enterprise text
8 lines Enterprise text
2 lines color lines
sync: 14+3+4+1+4
40+54+100+54+28+8+2+26=312
Sync: (here reload bit sets, so this is the end of LPT)
F2 92 3F 00 00 00 00 00 00 00 00 00 00 00 00 00
FD 00 3F 00 00 00 00 00 00 00 00 00 00 00 00 00
FC 00 06 3F 00 00 00 00 00 00 00 00 00 00 00 00
FF 00 3F 20 00 00 00 00 00 00 00 00 00 00 00 00
FC 13 06 3F 00 00 00 00 00 00 00 00 00 00 00 00”

Is the OSSC not capable of showing interlaced pictures?

[BuckoA51]

OSSC of course supports interlace, it could be your display struggling with the off spec mode though?

[JohnFante]

OSSC of course supports interlace, it could be your display struggling with the off spec mode though?

I thought the OSSC outputtet a standard format or does that vary depending on the input?

Sorry if this is a noob question 🙂

EDIT: Found the list. Will start testing my different displays 🙂

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