SMS Jailbars Solution

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WestRGB
Posts: 6
Joined: Wed May 03, 2017 11:17 pm

SMS Jailbars Solution

Post by WestRGB »

I'm looking to resolve the jailbars on my Sega Master System Model 1.

I have my SMS Model 1 hooked up through a gscartsw_lite, into a Framemeister, and then to my TV.

I understand there is an RGB Bypass available, but it uses a THS7314 with a low pass filter. And given that I run my setup through a Framemeister, I don't want to double up on low pass filters.

Can anyone on these forums tells me what is causing the jailbars? Is it interference from circuitry in the console? If so, can this be resolved by cutting unnecessary circuitry like composite video? Would a cap replacement help?

Any and all suggestions would be welcome.
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zeruel85
Posts: 150
Joined: Mon Nov 30, 2015 3:47 pm
Location: Italy

Re: SMS Jailbars Solution

Post by zeruel85 »

What I've done 'till now:

1) Used a THS7374 RGB bypass
2) Disabled CVBS
3) Disabled subcarrier
4) Did not recap the console

Unfortunately, jailbars are still there... :|
Sega90s
Posts: 29
Joined: Sun Jul 23, 2017 4:09 pm

Re: SMS Jailbars Solution

Post by Sega90s »

I have done a full recap and can confirm it does not resolve the jail bars.
Using a scart cable with csync did minimize them, but they are still visible in solid blue color backgrounds.
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cr4zymanz0r
Posts: 356
Joined: Sat Oct 19, 2013 6:36 am

Re: SMS Jailbars Solution

Post by cr4zymanz0r »

zeruel85 wrote:What I've done 'till now:

1) Used a THS7374 RGB bypass
2) Disabled CVBS
3) Disabled subcarrier
4) Did not recap the console

Unfortunately, jailbars are still there... :|
Did you disconnect or cut the traces for the RGBs signals coming out of the Sega 315-5124 chip so they were only connected to the RGB bypass board and not still connected to the SMS board?
Johnpv
Posts: 275
Joined: Tue Apr 04, 2017 4:46 pm

Re: SMS Jailbars Solution

Post by Johnpv »

cr4zymanz0r wrote:
zeruel85 wrote:What I've done 'till now:

1) Used a THS7374 RGB bypass
2) Disabled CVBS
3) Disabled subcarrier
4) Did not recap the console

Unfortunately, jailbars are still there... :|
Did you disconnect or cut the traces for the RGBs signals coming out of the Sega 315-5124 chip so they were only connected to the RGB bypass board and not still connected to the SMS board?
This is what worked for me. I did the RGB bypass mod, and cut the signals. No more jailbars on my SMS.
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zeruel85
Posts: 150
Joined: Mon Nov 30, 2015 3:47 pm
Location: Italy

Re: SMS Jailbars Solution

Post by zeruel85 »

cr4zymanz0r wrote:
zeruel85 wrote:What I've done 'till now:

1) Used a THS7374 RGB bypass
2) Disabled CVBS
3) Disabled subcarrier
4) Did not recap the console

Unfortunately, jailbars are still there... :|
Did you disconnect or cut the traces for the RGBs signals coming out of the Sega 315-5124 chip so they were only connected to the RGB bypass board and not still connected to the SMS board?
Disconnected. I will try to cut the trace when I have some free time and I'll report back.

Thanks
WestRGB
Posts: 6
Joined: Wed May 03, 2017 11:17 pm

Re: SMS Jailbars Solution

Post by WestRGB »

I appreciate the feedback from everyone. It sounds like gaming community is still trying to figure this one out.
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cr4zymanz0r
Posts: 356
Joined: Sat Oct 19, 2013 6:36 am

Re: SMS Jailbars Solution

Post by cr4zymanz0r »

Last night I installed a RGB bypass board for my SMS. It was better, but not perfect. Here are my results:

Before: Couldn't really see the jailbars on a 27" Trinitron modded for RGB, but they were VERY obvious on my HDTV via OSSC.
After RGB Bypass, original RGB traces NOT cut: It definately was better. The jailbars were still there but much more faint on the OSSC. I could see them up close, but could hardly tell when sitting a few feet back on the couch.
RGB Bypass, original RGB traces cut: Oddly, this didn't seem to change anything over the traces not being cut (at least as far as I could tell).

I'm much happier with it now, but the perfectionist in me is still annoyed :P. I'm beginning to wonder if some (all?) Master Systems have a design flaw similar to PC-Engine where there's not enough capacitance on the power filtering circuit for one of the video related chips. Investigating that is beyond my level of expertise, but I'd be happy to work with someone who does have the knowledge.
Johnpv
Posts: 275
Joined: Tue Apr 04, 2017 4:46 pm

Re: SMS Jailbars Solution

Post by Johnpv »

I don't know which bypass amp RetroRGB was selling back in early 2016, but that bypass amp, along with cutting the RGB traces worked really well for me. Mine were SUPER bad before that and like 99.5% gone after that.
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cr4zymanz0r
Posts: 356
Joined: Sat Oct 19, 2013 6:36 am

Re: SMS Jailbars Solution

Post by cr4zymanz0r »

Johnpv wrote:I don't know which bypass amp RetroRGB was selling back in early 2016, but that bypass amp, along with cutting the RGB traces worked really well for me. Mine were SUPER bad before that and like 99.5% gone after that.

I couldn't find one for sale anywhere so I ended up just ordering the PCB and populating it myself: https://oshpark.com/shared_projects/KiETPmh8
I wouldn't say 99.5% of the jailbars are gone for me though. maybe like 80% gone. There's a few different internal revisions of SMS that might affect things too.
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