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OSSC Fails to sync

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This topic contains 10 replies, has 5 voices, and was last updated by  marqs 6 months, 2 weeks ago.

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  • #19654

    Morden
    Participant

    Hello!

    Let me start by saying I love the OSSC. It is, by far, the best scaling device for RGB video I’ve had a pleasure of using. I got my unit early January, and thus far, using it has been a great experience. Until today. Unfortunately, something doesn’t work as it should, as the OSSC fails to sync with any and all RGB signal via SCART, which I’ve been using from the start.

    I was using the OSSC almost exclusively with my arcade hardware, on the same, unchanged setup. A Vogatek IV Supergun, a PC power supply, Supergun and OSSC were connected by a SCART cable, with no audio on the SCART lines. My OSSC is v1.6, by the way. I of course use a HDMI cable to connect the OSSC to my TV.

    I was trying to fire up Taito’s F3, which is notorious for its sync problems. It usually worked for me, after increasing the pre and post coast values to 4, and turning the OSSC off and on again after saving the settings. Once the image locked in, it would stay that way.

    Not this time. Instead I got some garbage on the OSSC display. The whole screen flickered, displayed random characters for a second, blacked out all of the letters, as if the contrast was screwed way up … this went away, but after that, I was no longer able to get a sync on ANYTHING. Neither the F3, nor any other board, which thus far gave me no trouble whatsoever.

    I did some checking, of course. I live in Europe, and my TV still has the SCART, so I tried connecting the F3 to the TV directly. It worked. So did every other board. CPS, CPS2, Neo Geo, PGM2 … It’s not a problem with the Supergun, nor the cables, nor the boards. Everything pointed to the OSSC.

    I checked the settings, I reset everything to defaults. Nothing. I can get the test pattern, but no image from the boards. CPS2 once popped in for a fraction of a second at startup, but disappeared again. The red diode is blinking, like with the F3, seemingly trying to sync, but no go.

    So I figured maybe the firmware got corrupted somehow. I followed the steps provided here, and updated from MicroSD to the latest audio-enabled firmware. No dice. Same thing. The OSSC won’t sync properly to arcade boards connected via SCART. I haven’t tested VGA or component inputs, but I haven’t used them once since I bought the device, as RGB is what I’m after.

    Being a relatively recent purchase, the OSSC is still covered by the warranty, and sadly, it appears that I will have to send it in, unless someone has some suggestions. Like I said, though. I haven’t changed my setup. The OSSC itself is placed in front of the TV, so it’s a well ventilated area. Overheating could not have happened. Help … I can’t go back to playing the games unscaled.

    #19662

    James-F
    Participant

    TV have 2 prong power plugs, but the orientation matters very much when interconnecting equipment.
    If I plug my 2-prong CRT in reverse I have 230V potential difference between equipment grounds !! that’s enough to fry any electronics.
    Check AC voltage with a multimeter between equipment grounds that run form different power sockets, and between each device ground (composite shielding) and power socket ground,, flip the reversed 2 prong plug to prevent accidents.

    #19668

    Morden
    Participant

    A small update. It seems that after some cool-down time, the OSSC can display picture from CPS2 and Neo Geo [haven’t tested anything else], but it only works for about 10 minutes or so. After that, the red diode will start blinking and lose the signal, until there is no picture at all, and “no sync” appears on the LCD display.

    I’ve been using the OSSC every day since I got it, and this never, ever happened with any of my boards. Not even the F3, once it locked onto the signal. I honestly have no idea what could be at fault.

    As for the TV prongs, my current TV setup hasn’t changed for years. I use arcade PCBs with it directly via SCART, but the TV’s scaling leaves a lot to be desired. That’s why I got the OSSC. Arcade boards get their power from an ATX PC power supply. I don’t know how this setup could have damaged the OSSC after working perfectly for so many years, without any incidents with all of my other equipment.

    #19697

    BuckoA51
    Keymaster

    Aren’t those superguns known for outputting nonstandard/TTL sync? I can’t remember if it’s that brand but that’s maybe the issue.

    #19703

    Morden
    Participant

    I wouldn’t know about Vogatek’s output sync, BUT … there’s definitely something wrong with the OSSC itself. To eliminate the possibility of the Supergun being at fault, I have tested the OSSC with consoles via RGB SCART and the symptoms are the same. It works for a while, but then, the screen goes black. It’s like that with everything now. Plus, the console image had some weird flutter on brighter colors, which I didn’t see before.

    Also, the Vogatek worked perfectly fine up until yesterday, and it still works when connected directly to the TV. I’ve had it for a while and never had any issues. I’ve used it with other scalers as well. No issues.

    I feel that at this point I have confirmed it’s an issue with the OSSC itself. How does the warranty process work and who do I need to contact to get things going? Thanks!

    #19737

    BuckoA51
    Keymaster

    If Vogatek Supergun is outputting TTL sync direct to the OSSC that may be the cause of the damage, especially at higher voltages (JAMMA video spec is all over the place). Damage caused by that wouldn’t be covered in the warranty unfortunately. However I can’t be 100% sure that’s the case. There were reports (from SuperG with his GScart) of people using similar Superguns with this issue and that causing his units to stop working.

    Could you open your JAMMA SCART cable and show a picture of the wiring perhaps?

    #19740

    Morden
    Participant

    The cable appears to be heat sealed or glued shut, but it’s a regular male to male SCART cable I got ages ago. The Vogatek MK IV has six resistors connected to different signals on the RGB socket, which I’m assuming is to make the signals safe for consumer electronics like TVs, or other devices with SCART input. It doesn’t send audio over SCART, though.

    Like I said, This is what I’ve been using for many, many years, and thus far, everything worked fine. I’ve connected this particular supergun to other scalers, to a DVD-R recorder and to different TVs. This would be the first time I’ve experienced any issues. Even now, when my OSSC is down, I continue to use it with my TV directly.

    I feel like I’m defending myself at this point. I’m well aware the cause of this can be any number of things, but all I can tell you are basically two things: During the last X years, I haven’t experienced any other unusual things or equipment malfunctions with my current setup, and the OSSC suddenly went bonkers after working perfectly fine for two months of every day use. And I do mean every day.

    It seemed quite random. I have played hours upon hours of Taito F3 games before, and even though many people claim they can’t even get a picture from the F3, I got one. Maybe I’m lucky. All scaling multiples work on my TV as well. Same goes for my PC screen. The display showed garbled characters for a fraction of a second, and that was that.

    Clearly, the OSSC is not completely dead. It does “work”, but only for about 10 minutes from power up, after a long cool-down period.

    How do you propose we handle this? I’d like nothing more than to continue using this great product. It wasn’t exactly cheap, so I can’t just say “oh well … I guess I’ll buy another one”.

    #19741

    marqs
    Participant

    The symptoms sound like a there might be a cold joint somewhere around the digitizer chip. Many Superguns have a resistor on the sync line, and even if not, I doubt sync driver on a typical arcade PCBs has enough driving strength to output more than 2V into 75ohm termination.

    #19747

    BuckoA51
    Keymaster

    Really I had heard that some boards go as high as 5volts on sync output? An exception rather than a rule though I’d imagine.

    Ok let’s RMA and swap this one however I’d strongly advise asking Vogatek if their hardware has proper 75ohm sync as it may be the case they simply weren’t aware of this potential problem.

    Just mail in via the contact form with your order number to start the process.

    #19756

    SirRockALot
    Participant

    I think this is something that could be improved in future OSSC revisions.

    Of course, the SCART spec and the OSSC documentation is clear on what type of sync signal is expected. And that’s all good and fair – if you i.e. fry your device with a 9V DC center-positive labelled power jack by hooking up a 12V DC supply, your fault.

    But I’d argue that the sync level issue is more insidious than that. Some cables have the resistor in the SCART head, some in the DIN plug. Some consoles output video level sync and don’t need a resistor. Some RGB mods and RGB output devices have a jumper to switch between the two levels. Sync strippers can also change the situation. Many makers of cables, RGB mods & superguns have apparently gotten this wrong over the years. A 10$ radio shack meter can’t tell you the amplitude of a sync pulse. If you get it wrong, at first nothing might happen. Picture looks fine, but a year later some switch, TV or scaler is damaged.

    My point is that making sure your sync signal has the correct magnitude is not easy for the average retro gamer. You either need complete knowledge and understanding of the video signal chain in your console, RGB mod & cable or you need to own & be able to operate a scope to be sure you’re not outputting the wrong levels.

    I think adding tolerance, or even better reporting, for TTL-level sync signals would be valuable.

    #19860

    marqs
    Participant

    5v sync output is expected from arcade boards that are designed for TTL load. However, sync signal is often driven by a logic chip which have limited driving strength – with a 75ohm load instead of proper high impedance load, the chips typically can output only around 1Vpp which should be still safe for most video-level inputs. I’ve not heard anyone damaging ossc sync input with any console yet, but arcade boards are naturally more likely to contain strong sync buffers. External buffers like this should also be avoided with scart inputs.

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