Damaged RGB CRT - was it the SMS' fault?

[bonzo.bits]

I connected my PAL SMS 1 to a Loewe CT1170 using a NTSC SCART cable for the first time. I didn't notice any problem with the picture but the sound wasn't coming out the TV speakers (EDIT: was using WBIII:TDT with the FM card on the wrong setting, so no sound was coming out of the SMS. Doh!) so I switched the SMS off after about 30 seconds. Then I remembered that the SMS is PAL (unlike all my other consoles) and that I might have damaged the RGB circuitry in the TV. (EDIT: per below replies this is an incorrect assumption due to PAL/NTSC for Sega using same pinout so no problem with the 12V line like on some other PAL consoles).

So I hooked up my SNES Mini via SCART to see if I'd busted the TV somehow. Sound from the SNES works fine - but now the picture is dark. I can't really explain in words, but for anyone familiar with 240P test suite, the test with the graded colour bars (red, green, blue, white) the first three or fours bars in each colour are no longer visible. The balance of the colours themselves is fine, it's more that the overall brightness is now lower than it should be. Prior to tonight, all bars were visible for all colours.

The picture has the same problem when connecting a JPN model 2 Saturn.

SNES Mini, Saturn and SMS were all connected using using C-Sync cables from RCA. SNES Mini was working fine earlier that day with the Loewe and the Saturn was working fine when last used about a week ago.

Before I put the SMS away, I connected it to the CRT via RF (not cos I'm some backward sicko, just for curiosity ) and the brightness issue does not exist. So my conclusion is that the damage must be limited to the SCART circuit itself.

Does anyone have any know-how in this regard? There don't seem to be CRT dedicated forums (EDIT: found some after refining search terms) so I'm hoping someone on here can point me in the right direction. I've played around with the contrast and brightness settings and also the service menu and the issue did not resolve.

On a side note, does anyone know what the bytes in the service menu do? I've been told to never mess with them, but I'd still be interested to know.

Edit: resolved. Damage was caused by crappy mod work I did on the SMS. Have added final post with details.

[Guspaz]

The SMS/Genesis use the same pinout globally, there is no such thing as a PAL vs NTSC SCART cable for those consoles. As to if a PAL signal would hurt an NTSC TV, I wouldn't think so, but I'm not an expert.

[ChuChu Flamingo]

Is the cable Csync? Maybe you weren't using a properly attenuated 75 ohm Csync

[bonzo.bits]

The SMS/Genesis use the same pinout globally, there is no such thing as a PAL vs NTSC SCART cable for those consoles. As to if a PAL signal would hurt an NTSC TV, I wouldn't think so, but I'm not an expert.

That's interesting. Well it would be quite the coincidence that the picture is not what is previously was. I'm no expert either, but the picture was perfect this morning when playing some F-Zero. Now after hooking up the SMS, the SNES doesn't look so good. My Saturn also has the same problem - IE, it was fine previously, but now it's not.

Is the cable Csync? Maybe you weren't using a properly attenuated 75 ohm Csync

I haven't had problems with the cable before - it works fine with a Genesis 1 to the same display (EDIT: incorrect. Have never previously connected the Genesis to the CRT. This was the first time connecting either the SMS or the Genensis SCART cables to this display). The cable works fine with Genesis to OSSC and Framemeister. Have never tried it with the SMS to those, only with HDR's component cable for genesis - and it worked fine. (EDIT: The SMS has a 50/60Hz switch and neither the FM nor the OSSC liked that, hence I was hoping the CRT would make nice with the SMS and I'd finally see it in RGB glory for the first time and without stutter. )

[Xer Xian]

As already suggested (and can be seen from here), the SMS and the MD/Genesis have the same pinout, so if you've already succesfully used the same cable with your Genesis, it's difficult to figure out what went wrong. PAL vs NTSC encoding doesn't have anything to do with RGB btw, and anyway your TV is german so it'll be happy to take PAL anytime (as you must have realized yourself by hooking up the SMS through RF).

[ChuChu Flamingo]

The SMS/Genesis use the same pinout globally, there is no such thing as a PAL vs NTSC SCART cable for those consoles. As to if a PAL signal would hurt an NTSC TV, I wouldn't think so, but I'm not an expert.

I haven't had problems with the cable before - it works fine with a Genesis 1 to the same display. Also works fine with OSSC and Framemeister.

So do other scart cables work on that tv? The reason I state this is recently people have been finding out some scart cables don't attenuate csync to 75 ohms or even amplify it. If im not mistaken I think the Genesis outputs an abnormally high TTL csync level that can damage certain equipment if not attenuated correctly. Not sure if master system has the same high TTL csync.

A few people have reported their framemeisters and other stuff dying probably due to this. With this in mind, it isn't like it instantly kills your shit, more so reduces its lifespan and puts more load on it pushing it past the intended spec. The guys at theretro roundtable had a good discussion on this.

[theclaw]

The SMS/Genesis use the same pinout globally, there is no such thing as a PAL vs NTSC SCART cable for those consoles. As to if a PAL signal would hurt an NTSC TV, I wouldn't think so, but I'm not an expert.

I haven't had problems with the cable before - it works fine with a Genesis 1 to the same display. Also works fine with OSSC and Framemeister.

So do other scart cables work on that tv? The reason I state this is recently people have been finding out some scart cables don't attenuate csync to 75 ohms or even amplify it. If im not mistaken I think the Genesis outputs an abnormally high TTL csync level that can damage certain equipment if not attenuated correctly. Not sure if master system has the same high TTL csync.

A few people have reported their framemeisters and other stuff dying probably due to this. With this in mind, it isn't like it instantly kills your shit, more so reduces its lifespan and puts more load on it pushing it past the intended spec. The guys at theretro roundtable had a good discussion on this.

I wouldn't be surprised. You're not supposed to use the straight rgb lines of most consoles. Those resistors, capacitors, and all aren't just for show.

[bonzo.bits]

So, we can exclude pinout as the source. Thanks for that

It could be any of these then:

A) Either the console or SCART cable has missing/faulty/incorrect componentry, causing too high of a signal (voltage?) to be delivered to the display and this has caused damage to components in the TV.
B) The display was due to go anyway and it's just a coincidence that it occurred when hooking up this particular cable/console combo for the first time
C) Unknown environmental condition

Does this sound like an adequate approach for investigating A?

- Obtain schematic for PAL SMS
- Identify RGB circuitry and other signals feeding to multiout on SMS
- Check voltage levels are within acceptable range
- Check resistors/capacitors are resisting/capaciting correctly
- Perform same tests on SCART cable

...240P test suite, the test with the graded colour bars (red, green, blue, white) the first three or fours bars in each colour are no longer visible. The balance of the colours themselves is fine, it's more that the overall brightness is now lower than it should be. Prior to tonight, all bars were visible for all colours.

I was hoping that someone with CRT tech know-how could infer from this a starting point for the investigation. Anyone?

[bonzo.bits]

Another question for any RGB signal / circuitry guru that might take a peep in this a thread, is it possible that installing the (super primitive) 50/60hz mod that is just a switch (IE, no new crystal, no DFO) could cause damage to the RGB equipment? There's also one of eTim's FM sound boards installed in the SMS. It was in the machine when I bought it, at a cursoryglance it appears to have been a shit install job.

I haven't gotten around to any of the investigation mentioned in previous posts.

[matrigs]

http://www.sega-16.com/forum/showthread ... cart-Cable

Try removing the caps from the colour lines in the cable.

[theclaw]

Another question for any RGB signal / circuitry guru that might take a peep in this a thread, is it possible that installing the (super primitive) 50/60hz mod that is just a switch (IE, no new crystal, no DFO) could cause damage to the RGB equipment? There's also one of eTim's FM sound boards installed in the SMS. It was in the machine when I bought it, at a cursoryglance it appears to have been a shit install job.

I haven't gotten around to any of the investigation mentioned in previous posts.

Unlikely but not impossible. A 50/60hz switch without adding the appropriate crystal oscillator is technically incorrect.

[gray117]

... what's happening to the sound on all your scart consoles? If all using that scart cable are off I'd suspect cable in some manner.

... if it's just the sms that is off, then yep something is wrong with sms. Is the audio also not working with composite cable? Is the sms cause of your knackered picture? Probably more coincidence, BUT, I'd avoid it and focus on getting something like your saturn looking right.

Assuming the color/darkness shift is outside normal adjustments you're probably going to be looking at capacitors around anything to do with scart/rgb specifically. Likely failing but not failed/burst. This can make it difficult to diagnose, and almost a case of pot-luck replacement (not a bad thing to do but a pain in the arse even if your good at doing it and assuming you can reach/identify said caps).

If you get your saturn looking right, I'd make sure you know what's going on with that SMS and that it's fixed up to best of knowledge before plugging in. I'd still be inclined to think this is just coincidence/bad luck - but the lack of audio is an interesting standout - that should just be working the same for all scart-connected consoles ... unless there was something particularly broken in regards to that sms (aside from the issue of whether or not that 'broken-ness' was the cause of your picture woes, or just another coincidence).

[bonzo.bits]

... what's happening to the sound on all your scart consoles? If all using that scart cable are off I'd suspect cable in some manner.

Erroneous conclusion on my part, have edited initial post. Lack of sound was caused by incorrect FM card setting for WBIII. SMS and all other consoles are outputting sound find, it's just the image brightness issue.

Probably more coincidence

Agreed.

Assuming the color/darkness shift is outside normal adjustments you're probably going to be looking at capacitors around anything to do with scart/rgb specifically. Likely failing but not failed/burst. This can make it difficult to diagnose, and almost a case of pot-luck replacement (not a bad thing to do but a pain in the arse even if your good at doing it and assuming you can reach/identify said caps).

This is pretty much what I'm thinking. Now that I've obtained the TVs service manual from the helpful Loewe customer service crew, next step will be to study the schematics, ID the R, G, B and sync lines (and any other ones that might be relevant) and then check the components there. Last time I switched on the TV there was continual crackling/buzzing noises (arcing?) coming from the rear near where the SCART socket is, so I'm guessing that's an indicator something is busted.

[bonzo.bits]

So I pulled apart the head of the SCART cable, there is some sort of circuit in there - I'm not sure if it's for C-sync buffering or is one of the naughty sync-boosting circuits that can damage equipment. Given that my TV wigged out after the first ever time using it....

I checked my other cables (SNES C-Sync, SNES Luma, Saturn C-Sync) and they are all free of this circuit, thankfully

[bonzo.bits]

Pics

[xga]

Now that I've obtained the TVs service manual from the helpful Loewe customer service crew,

You mean to say that the Loewe customer service staff in Germany happily provided you with the service manual for a 20+ year old CRT TV? That's pretty impressive if so. Contacting manufacturers for service manuals of old TVs and monitors is usually met with the response of "Sorry, no longer available...".

[bonzo.bits]

Now that I've obtained the TVs service manual from the helpful Loewe customer service crew,

You mean to say that the Loewe customer service staff in Germany happily provided you with the service manual for a 20+ year old CRT TV? That's pretty impressive if so. Contacting manufacturers for service manuals of old TVs and monitors is usually met with the response of "Sorry, no longer available...".

Yep. I knew it was a moonshot, but they came good. Initially they sent the user manual, then sent the service manual after o asked again.

[bonzo.bits]

An update for anyone curious on how this is progressing. Latest observations indicate that it might be the console itself. Reason being, that when connecting the console > HDR component cable > OSSC > HDTV it is not doing weird stuff with the video signal. Say, for example, in certain games with a lot of blue graphics (surfing stage in California Games) the picture changes it's overall colour. It basically becomes more blue. Happens sporadically, most of the time the video output looks minty.

Given two different cables, two different displays + a linemulit device, and the SMS is still causing weird, new conclusion is something amiss in the SMS. Once I get around to it, I'll give it a clean and then investigate the RGB circuit and see if anything's amiss there.

Also, I contacted RCA and it's definitely NOT the cable that caused any of these problems. I have a Genesis 1 cable with the sync buffering circuit - not the booster circuit. Must have just been a aging or environmental issue occurred in the ~8 months since I last hooked up and played the SMS.

[bonzo.bits]

Took the SMS apart for a good cleaning, found that the culprit is a poorly installed 50/60hz switch. I didn't use enough solder when connecting the wire to the IC and it had disconnected. As far as I can tell, this led to two outcomes:

- Wrecked some part of the RGB circuitry in the CRT
- Caused the OSSC to be unable to lock onto sync. Which was shown by alternating Hz numbers on the OSSC LCD display

Not really helpful to anyone, other than a reminder to do your best work when installing mods