OSSC PRO settings for Atari 1040STe

[Felipe Rios]

I have the OSSC v1 and recently purchased the OSSC PRO (both from VGP).  The OSSC worked out of the box with my ATARI ST, the PRO does not.  It tries forever to sync and it is unable to get a lock. I tried all modes and tried adjusting some of the settings based on the original OSSC, but nothing works.

Does anyone use the PRO with an ATARI ST that can share any custom settings?  Or maybe my OSSC PRO is defective and I should send it back.

Thanks!

Fell

• This topic was modified 1 week, 3 days ago by Felipe Rios.

[marqs]

I’m not aware of anyone having tried Atari ST(e) with Pro, but some time ago I debugged one 7800 that didn’t sync. In that case the reason was cable, or fundamentally bad design from Atari. Essentially pin 2 of the AV connector carries either composite video or TTL composite sync depending on the model. If you happen to have RGB cable designed for the other sync circuit type, you may end up with sync level which is either too weak or high enough to potentially damage modern receivers. If the cable is suitable, you could try adjusting Analog sync Vth on Pro’s sync menu (although this should not be needed if sync level is right).

[Felipe Rios]

Thanks for the reply.  I tried a VGA cable that works fine with the OSSC but didn’t work with the PRO.   Then I tried another SCART cable and had the same issue, but I changed LPF to (2.5) and the Atari GEM screen appeared but rolling vertically!   I have no idea what to change to make it stable.

The PRO works with my other computers without any adjustments just like the original OSSC.   It’s the weird ATARI ST video output that the PRO is no longer able to handle.   If there is no settings fix, I will continue using the OSSC and use the PRO just for the C128 and Apple IIGS.

[BuckoA51]

Did the SCART cable you tried tap composite video for sync or did it have some kind of internal sync combiner?

[Felipe Rios]

Both scart cables are supposed to be RGB to Scart but I don’t know if composite pins are connected. I would have to take it apart.  I do have another Atari ST Scart cable from Cool Novelties. I will try that one.

[TheCorfiot]

Hi Felipe

ST and STe scart cables are notorious for sync issues where scart cables are concerned…

This is because they don’t natively have 5 or 12 Volts on the monitor connector which is usually used by other systems to derive the Fast blank switching voltage on scart Pin 16 which TV’s need to be informed to use RGB signalling instead of composite video.

Instead a “hack” which works most of the time was used using the Vsync signal and a 10uF capacitor to ground to provide a “rough” blanking voltage.

And Yes commercial cables used this.

The OSSC and Pro have no need for a fast blanking signal.

If you don’t mind trying an experiment…

Open your scart plug and look at pin 16… if it is connected by a wire then snip it.

Please double check your numbering….I cannot be held liable.

By all means upload a picture or 2 of your scart so we can advise further.

 

Most ST scart cables have

150R inline RGB resistors

330R inline CSYNC (pin20) resistor

• This reply was modified 6 days, 17 hours ago by TheCorfiot.

[Author]

Posts