nugat
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Post by nugat on Jul 16, 2014 11:44:49 GMT
Hi all I've been the proud owner of a PAL Sega Saturn for a number of years now and a couple of weeks ago I picked up a Japanese model HST-3200 to enjoy some of the Japanese games releases in NTSC glory. The Saturn was sold as faulty owing to the video output having a lurid green tint to it. I thought what the heck, it sounds like something that could be fixed so I'll have a play. If it's beyond help I'll keep it for spare parts but it would be nice to try and save it. I've tried a few things so far without luck, so if anyone has any ideas or could point me at something specific I should be looking at it would be much appreciated I've included a video and photos below so you can see the problem. Basically the screen is green Apart from that it works fine, there's no random video corruption and it doesn't crash. An interesting thing I have noticed is that any pixels that are supposed to be bright white appear as a magenta colour on the screen. If the intensity of the magenta pixels is lowered by the game they go back to a 'normal' colour. This can be observed if I play Street Fighter and press the pause button. Pausing the game lowers the brightness of the overall screen and any magenta areas disappear. I've included two photos which show this. Here's what I've tried so far :- - Three different RGB video cables, one purchased from consolegoods.co.uk. There is no difference between any of the cables. - Opened up the Saturn and given it a good clean, it only had a small amount of dust in it. - I've re-flowed the solder on the video port pins and checked the continuity between the port holes and the motherboard solder pins, they all seem fine. - I've had the Saturn running with the motherboard exposed and poked at various chips etc with a plastic implement. Paying particular attention to the video encoder (IC21?). So far I have been unable to trigger any change in the video output. - Visually inspected all capacitors including those on the power supply, non look blown. However it's difficult to tell as apart from the orange decoupling capacitors, they're all of the small silver can type variety (see photos). Erm, that's about it really, any suggestions welcome Video : Photos: Street Fighter paused and un-paused. Mainboard photos :
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Post by zyrobs on Jul 16, 2014 18:52:39 GMT
It seems the blue color is entirely missing... I'd look into that. You should check the schematics on the service manuals to see which components it goes through, and then try changing out those. It goes from VDP2 -> IC21 -> video output, with a couple of caps and resistors inbetween. We have detailed VA0 schematics so that should be possible to figure out.
I'd definitely recap the machine as a start, those type of caps are known to be dodgy in other systems.
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fightingvipers
Saturn Gamer
Fucking circles, how do they work?
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Post by fightingvipers on Jul 16, 2014 19:27:45 GMT
I agree looks like a video issue, it also looks kinda like NTSC through a pal tv, usually just black and white.
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nugat
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Post by nugat on Jul 16, 2014 20:01:27 GMT
Thanks for your responses. Yes now you mention it it does look like the blue is missing, you can see some shades of red and plenty of green, but no blue. I'll start with re-capping the main board as you suggest. Do you think it's safe to ignore the orange/brown ones (em4, em5 em6, etc) for the time being? They have three legs and there are loads of them so unless they're likely to be the cause it would be nice not to have to replace them Sorry if this is obvious but where would I get hold of the schematics?
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Post by zyrobs on Jul 16, 2014 21:34:44 GMT
I'd recap the stuff around the vdp2 and the video encoder first, specifically the stuff that touches the video lines (and out of those, first the ones that go through the blue signal). Then the PLL (ic20). If those do not fix the problem, recapping other stuff may not help much. Since the problem globally applies to everything and games run fine otherwise, I'm thinking that the problem lies between the VDP2 and the final video output.
EM4-5-6 etc are three terminal capacitors used for EMI filtering... also a possible candidate, though I've never seen those go wrong so badly before. Also, I don't know if they are still being manufactured? Seems only Murata makes them now?
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Post by zyrobs on Jul 16, 2014 21:39:26 GMT
Here are the schematics for VA0 machines: saturn_va0_schematics.rar 61.2 MB mega.co.nz/#!MxdQBarZ!3Qn6chcxR-VMDCKhWuu8k1W-dZxek3AGr3yHM1rzaRY The Japanese one is practically reverse-engineered - but it is also vectorized, so very useful even with the language barrier. You can use the English one to look up what part is what, as that one is a full scanned service manual.
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nugat
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Post by nugat on Jul 16, 2014 22:17:54 GMT
Brilliant, thanks very much for taking the time to advise. I'll let you know how it goes after I've replaced some of the caps.
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supersega
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Post by supersega on Jul 23, 2014 21:31:04 GMT
I have to throw my hat in the ring; seems to be a PAL/NTSC video thing. Could you try on an American or JPN TV?
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nugat
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Post by nugat on Jul 24, 2014 14:18:01 GMT
I have to throw my hat in the ring; seems to be a PAL/NTSC video thing. Could you try on an American or JPN TV? Thanks for the suggestion. I'm afraid I don't have an American or Japanese television to test with. However it was my understanding that as long as you're using RGB and your TV supports NTSC it doesn't matter? Since my last post post I wired up a cable to test the composite video output of the Japanese Saturn. It displays a black and white picture as you'd expect on a UK telly, however the weird magenta bits that are present on the RGB output are still there (but in greyscale). I have now ordered a complete set of replacement capacitors for the mainboard, a new soldering station and a few other tools to help me. I could have bought two working Japanese Saturns with the money I've spent LOL, but at least I'm now set up well for future repairs. I thought ordering the caps would be easy but it turned into a bit of a chore after I started researching which manufacturer/model to buy. I ended up ordering the capacitors from uk.farnell.com/ as they seemed to be the only place that stocked all the correct values in the Panasonic FC series, which are 'good caps' apparently There's a lot of info about such matters on www.badcaps.net if you want to waste a few hours of your life you'll never get back
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Post by zyrobs on Jul 24, 2014 15:37:49 GMT
I have to throw my hat in the ring; seems to be a PAL/NTSC video thing. Could you try on an American or JPN TV? PAL/NTSC issue would get you lack of colour. Here, only one colour channel from the three are missing. So definitely not a PAL/NTSC problem.
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nugat
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Post by nugat on Aug 3, 2014 12:10:59 GMT
So I replaced the 20 of electrolytic capacitors this morning in the vicinity of IC21 (video encoder) and IC20 (PLL), unfortunately it hasn't made any difference. On the positive side, it's the first time I'd done surface mount soldering and I managed it without making it worse than when I started I also re-flowed the solder on all the pins on VDP2 and IC20 just to make sure there were no dry joints. So what next? I might try to get hold of a replacement for IC20 (Sony CXA1645M), as I'm fairy confident that I could solder a new one in. If that fails then I'm out of ideas and I think I'll be on the lookout for another Japanese Saturn (a working one this time! . For anyone wondering how to replace the caps I found this method to be the easiest. - Cut off the old cap with a pair of flush cutters. - Clean up the solder pads using solder wick, make sure to remove any cap legs that may have been left behind. - Reapply new solder to just one of the solder pads. - Apply solder flux to both pads. - Position the new cap using tweezers or fingers and solder one side to the pad you put new solder on, you shouldn't need to add more solder. - Now it's tacked in place you can solder the other side of the cap. I used a temperature controlled iron with the temp set between 320C & 380C depending on the size of the component. I used a 0.8mm chisel tip.
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nugat
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Post by nugat on Aug 28, 2014 15:57:18 GMT
A further update on this, I bought a brand new Sony CXA1645M chip from everyone's favorite auction site and replaced IC20. Guess what, it has made no difference at all! :-) Whatever is causing the green screen is not capacitor related and it's not video encoder related. When a get some spare time I might go over the VA0 schematics again but for the moment I'm stumped! For anyone wanting to replace chips of this type, it really was quite easy. I actually found replacing the capacitors more difficult. I invested in some Chip Quik to remove the old chip, without that it would have been a different story. To save me typing, here's a video I found showing the procedure... www.youtube.com/watch?v=UmD7F0--7Lc
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kikenovic
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Post by kikenovic on Oct 16, 2014 17:38:46 GMT
Amazing all the work you did on the "Hulk" and still the same. I hope you haven't given up.
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