Colour issue using my new OSSC Pro with a DOS PC – no problem with OSSC v1.8

[Merkurio]

Dear OSSC Pro users, Dear Forum members, Dear Markus,

 

I have to ask you for your expertise/help concerning colour problems with my new OSSC Pro using with my DOS PC (ISA graphics).

The problem is: to have no colours – only levels of gray/fawn – when booting up DOS (first catching my eyes the missing of the common yellow lettering of AMI BIOS infos) and by using common DOS-programs (e.g. as Turbo Pascal, VGA-Copy, Star Commander …) –> BUT using the same setup (DOS PC – ISA graphics, monitors) with my OSSC v1.8 everything works fine !!! – please see my added pictures to compare

I don’t have an idea, if this is caused by a real technical defect/bug of my copy of the OSSC Pro or if it would be eventually cureable by a fine tuning (I tried out some – without effect – but I have no plan to go deeper with) ???

It’s strange, but colour is present, when starting a DOS game like „Prince of Persia“ or when starting up Win 3.11 from DOS level …

 

I went for the OSSC Pro vs. the common OSSC v1.8 to have origin screen aspect ratio of my DOS machine –> that works really fine

I used factory settings on my OSSC Pro as well as on my OSSC v1.8.

I also tried to flash firmware v0.77 once again new. (I have no access to older firmware versions, to try them v0.76 … – maybe it’s worth trying ?)

I hope you have an idea, what I could maybe try in fine tuning ? – maybe it’s a known issue … ?

For now, I’m rather thinking of a hardware defect !? Matt Buxton suggested to me, to post in your forum first.

 

Many thanks in forward for your inputs & Sending many greetings from Austria

Mario

 

 

[Merkurio]

attendum:

… DOS game „Prince of Persia“ or starting up Win 3.11 from DOS level works just fine.

 

[BuckoA51]

Quick question, do you get the same problems in line multiplier mode as well as scaler mode?

[Merkurio]

Hi back BuckoA51,

Yes, I get the same screen pictures in line multiplier mode – adaptive or pure …

 

[Merkurio]

Hi U all once again,

 

In the meanwhile, I found my problem solved by going this procedure:

1. connect my OSSC Pro as recommended to display and power supply – power OFF

2. let boot up my DOS machine COMPLETELY – without VGA connection to OSSC Pro !!!

3. after that – plug in VGA-cable to the OSSC Pro – then turn it ON

4. everything works in colour as it should do !!!

5. YES 👍👍👍

 

Many greetings from the Alps,

Mario

[BuckoA51]

Still it’s quite some mystery why you would need to do that, a simple power cycle of OSSC Pro is not enough?

[Merkurio]

Since now, no chance getting colours by having connected the VGA-cable during DOS boot process !

If I need to enter BIOS I have to accept “monochrome like style”

It seems, my OSSC Pro is kind of sensitive for some “signals” out of the VGA connection from my ISA graphics (TSEN LABS ET4000) during running DOS boot process …

I also tested with my second (faster) DOS machine – this has PCI graphics – with no issues & having colour also during boot process; very very strange of course😎

Thanks a lot,

Mario

[marqs]

Does the same happen in scaler mode with framelock turned off (60Hz option)?

[Merkurio]

Hi back marqs,

Yes, the same problems also happens with framelock turned OFF (60Hz, 50Hz, …)

 

p.s.: in the meanwhile I also found out, that the issue doesn’t occur (means colour is present correctly), in case of:

1. starting up my DOS machine as described in post #64799, followed by

2. computer “warm boot” (ctrl old delete) from the running DOS

–> it seems the whole issue will be determined in the first phase of “communication / hardware contact” between my OSSC Pro & my ISA graphics …

p.p.s.: yesterday I have also ordered a “new” graphics (with VESA Local Bus) at ebay – maybe I could report in some weeks how this will work …

 

Thank’s a lot,

Mario

 

[Merkurio]

… just opened my DOS machine – my graphics is the: Tseng Labs ET4000AX P/N 9109 REV (ISA-version)

[marqs]

It might be also worth trying to adjust sampling phase if in the unlikely case auto mode locks into a tiny time slice the card perhaps outputs monochrome.

[Zacabeb]

It could be an issue with the ID pins making the graphics card think the OSSC Pro is a monochrome device, replicating a monochrome signal across all three RGB outputs.

How does the OSSC Pro behave with VGA sources that don’t have DDC?

[marqs]

DDC pins are floating on both Pro and Classic, but pin 4 (ID2) is terminated with 75ohm to GND on Pro to enable video-level composite sync connection via AV adapter. Most VGA cables have this pin unconnected / grounded so it makes sense to try another VGA cable (preferably modern one) if that is the cause.

[Merkurio]

Hi back marqs,

ad #64814 concerning sampling phase, I tried out some “turn off AUTO” – but maybe you could tell me the exact OSSC Pro’s menu item, you mean ?

ad #64818 concerning VGA-cable & pins, I tested with circuit indicator/checker every pin-pair (from end to start of my cables) – especially pin 4 (ID2) with no issue found.

The only thing, I could find out, which is different comparing my cable to the schema (from internet) below is: only pins 6, 7 & 8 (RGND, GGND, BGND) are short circuited – pin pair 10 (SGND) and pin pair 5 (GND) are separeted / not connected together – but I think that wouldn’t matter … ?

For that moment, I only have access to two (new) VGA-cables with the same colour issue, but I will have it in mind to try out others …

Many thanks,

Mario

 

[Merkurio]

Hi back Zacabeb,

I think, you hit the problem exactly !

I’m also thinking, something is “making the graphics card think the OSSC Pro is a monochrome device”

As I wrote before (#64810) it’s very strange, that:

A. the failure doesn’t occur doing warm boot (ctrl old delete) from a running system but

B. the failure does occur doing boot with the reset button from a running system

With my second DOS machine (PCI graphics) everything runs in perfect colours !

For the future, I would like to try my C128/C128DCR’s in 80 Columns Mode with CGA2RGBv2 – unfortunately in that moment I don’t have access neither to this nor to any other VGA sources …

Thanks a lot,

Mario

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