Atari STE - no monitor output, RF fine

[Hellraiseruk]

Hi all,

Just acquired a 520 STE (which I shall be recapping later today), I also ordered a Cool Novelties RGB SCART cable which seems to get good reviews. Powering up the STE and using RF gives me a picture as I would expect, however using the RGB SCART cable gives me a blank screen and shows "no signal". Now, this particular TV I have used with both an Amiga and a Spectrum 128 over RGB with no problems so it definitely supports RGB. I have also used a separate RGB SCART - HDMI converter, and this also doesn't recognise any kind of signal (and is known to work with RGB sources).

Before I start poking around, has anyone come across this before? No worries if not, it'll be something for me to troubleshoot once I've recapped the PSU, but if there's a quick fix or I'm doing something stupid then it would be good to know

[stephen_usher]

It's quite possible that the other SCART cables have a voltage on the detect pin which tells the TV to use RGB rather than composite video and the Atari one doesn't, so it's trying to use the composite input pins.

[Hellraiseruk]

Yeah part of my troubleshooting will involve checking for bad solder joints on the socket then making up a bodged AV cable from pin 2 (composite) to the AV input, just to see if I get a pic thru composite. Then it'll be multimeter and oscilloscope time I was under the impression the Cool Novelties cables were good though, and worked fine? Having popped the scart plug open it looks like a quality job, resistors on the RGB lines and a capacitor on the blanking line, so would expect all to be fine. Might have to get the old 14" CRT out the loft and see what that does!

[rubber_jonnie]

Yeah part of my troubleshooting will involve checking for bad solder joints on the socket then making up a bodged AV cable from pin 2 (composite) to the AV input, just to see if I get a pic thru composite. Then it'll be multimeter and oscilloscope time I was under the impression the Cool Novelties cables were good though, and worked fine? Having popped the scart plug open it looks like a quality job, resistors on the RGB lines and a capacitor on the blanking line, so would expect all to be fine. Might have to get the old 14" CRT out the loft and see what that does!

CoolNovelties cables are great, it's likely to be some other issue like no 12v at pin 8 of the video socket. You can check this on the SCART connector as it is also pin 8 IIRC.

[Hellraiseruk]

Right, troubleshooting done and I'm confused! Got an Atari 520 STE, recapped the PSU, sorted mouse ports and now just need to figure out why I get no video from the monitor jack.

For the record, RF output is fine - audio and video, as good as RF gets. If I hook up my RGB SCART cable, I get no signal on my upscaler, and no signal on my LCD TV. Hooking it up to a 14" CRT, I get a rolling picture that is green and pink (!) with horizontal tearing and black horizontal bars, so looks like a sync issue. Tried another cable, same problem.

I thought I'd check C415 which is installed backwards from the factory and can cause issues, replaced that, put it in the correct way same problem.

I've had a look at the monitor port, checked for connectivity, no problems, made a patch lead to an RCA plug from pins 2 and 13 to see if I could get a composite signal out, but no output. Checked with a multimeter, and it looks like there is a dead short between pins 2 and 13. Is this right? Am I reading some kind of parallel path?

Any help would be appreciated

[Steve]

You haven't mentioned it you checked pin 8 for 12v yet?

[Hellraiseruk]

Yep, 12v on pin 8. Crt shows RGB on the OSD so it's recognising an RGB signal, just doesn't seem to quite know what to do with it. Slightly concerned about the apparent short between pin 2 and 13, will have another look tomorrow and trace it all back to the MC1377.

Cheers

[Hellraiseruk]

Would someone with an STE be so kind as to measure resistance between pins 2 and 13 on the monitor port for me please? I'm pretty sure it shouldn't be a short to ground, but who knows As everything works via RF I'm at a loss as to where the issue may lie, as the composite signal is obviously intact at the RF modulator, so there's very little else to go wrong. I had money on that capacitor (C415) being the issue, was so disappointed when it made no difference

[Steve]

This website I found seems to be very informative, perhaps one of his methods could help?

http://www.florentflament.com/blog/gene ... ignal.html

EDIT: I think your problem is solved in my next post with Gadget UK using the exact same SCART cable as you.

[Steve]

Also the more I read about it, even though you say:
"Now, this particular TV I have used with both an Amiga and a Spectrum 128 over RGB with no problems so it definitely supports RGB. I have also used a separate RGB SCART - HDMI converter, and this also doesn't recognise any kind of signal (and is known to work with RGB sources)."

I think the Atari generates the sync signal differently to those computers you mention. So it could simply be a compatibility issue between the Atari and the TV. Maybe you need to try on more 15khz capable screens, or get an OSSC, or try and make a clean c-sync cable like in the article I linked.

Also here Gadget UK has the same problem as you, with SCART, and he fixes it here:



The more and more times I see problems concerning computers, the answer almost always is solved using occams razor.